Using MLAG in Dell Networks v1.3

7/23/2019 Using MLAG in Dell Networks v1.3

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A Dell Deployment and Configuration Guide

Using MLAG in Dell Networks

A deployment guide for Dell Networking switches (version 1.3)

Dell EngineeringFebruary 2015

January 2014

d



2 Using MLAG in Dell Networks v 1.3

Revisions

Date Description Author

February 2015 1.3 contains full-mesh support with VLT, new method to single-

home devices to one Peer, and improvements on “show” reporting from the secondary Peer.

Victor Teeter

August 2014 1.2 clarifies native VLAN assignment on the Peer-Link; solutions

for single-homing a Partner device to one Peer.

March 2014 1.1 includes changes to full-mesh support with VLT, limitation

of Partner switches, and added clarification of ports that can be

used in Peer-Links.

January 2014 1.0 Initial Release.

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Contents

1

Introduction .........................................................................................................................5

2

Caveats for Enabling MLAG ............................................................................................. 6

3 Supported Topologies ...................................................................................................... 8

4

Single-Tier Example .......................................................................................................... 9

5 Two-Tier Example ............................................................................................................ 13

6 Connecting Single-homed Partners ........................................................................... 19

7

MLAG with VLT ................................................................................................................ 22

8 Additional Resources ....................................................................................................... 31

Appendix ................................................................................................................................ 32

Support and Feedback ........................................................................................................ 33

About Dell .............................................................................................................................. 33




Executive Summary

Multi-switch Link Aggregation or MLAG is a feature that allows two Dell Networking switches to act as a

single switch, providing multiple paths across the network and offering benefits such as:

Failover in cases of failed cables or switches Increased bandwidth of up to double the bandwidth of a single switch

Elimination of port blocking and reconvergence delays of spanning tree

An MLAG domain is created by connecting a Dell Networking switch to another Dell Networking switch

through Peer-Link ports to create MLAG Peers (the two connected switches). Other switches directly

connected to the MLAG Peers are unaware that they are connecting to two switches, which appear as a

single switch on the network.

All links in the MLAG can carry data traffic across many physically diverse topologies. In the case of a link

or switch failure, traffic continues to flow with minimal disruption. MLAG optimizes availability and

bandwidth between attached devices in Dell’s Datacenter and Campus networking solutions.

The following Dell Networking N-series switches support MLAG and may be used in building the

configurations in this guide:

N2024 N3024 N4032

N2024P N3024P N4032F

N2048 N3024F N4064

N2048P N3048 N4064F

N3048P

Note: Dell N15xx Series switches do not support MLAG.




1 Introduction

MLAGs provide an active-active split aggregation deployment across two switches acting as one,

creating a more resilient network with higher bandwidth capabilities. This guide discusses MLAGs,

how and when they are used, caveats to look out for, and instructions on how to implement MLAG

into your network.

Figure 1 shows two very basic examples of MLAG domains. In both examples, Peer switches are linked

together with a special LAG (one or more cables as denoted by red lines in the pictures below), called a

Peer-Link. Any non-management port on the switch can be used in the Peer-Link. With the Peer-Link

configured, the two switches appear as a single switch to Partner switches upstream and downstream.

Each Partner switch contains MLAGs that are simply LAGs (Link Aggregation Groups) whose cables are

split between the two Peers. Primary and secondary Peer roles are automatically assigned by the switch

firmware when MLAG is enabled.

MLAG

Secondary MLAG peerPeer-Link

MLAG

Secondary MLAG peer

Peer-Link

MLAG

Primary MLAG peer

Primary MLAG peer

Partner Switch

Partner Switch Partner Switch

MLAG domain

appears as a single

logical switch to

partner switches on

the network

Simple L2 MLAG

L3 MLAG with mulitple

partner switches

MLAG domain

MLAG domain

Two examples of a single-tier MLAG topology




2 Caveats for Enabling MLAG

Here are a few requirements when implementing MLAGs:

Same series switch models are required to create MLAG Peers. This means any N2000 Series can

only be peered with another N2000 Series, an N3000 Series with another N3000 Series, and an

N4000 Series with another N4000 Series.

Peer devices must use the same expansion module type if ports from the expansion module are to

be part of the MLAG interface.

Neither of the two switches used as MLAG Peers may be stacked with other switches.

See the switch User Guide for additional information.

Spanning Tree

Examples shown in this paper are running Spanning Tree protocol RSTP. MLAG supports MSTP as well but

does not support RPVST. Be sure all devices have the appropriate configuration regarding the spanningtree protocol used.

Consistency of MLAG Peers

As mentioned above, the two switches used as MLAG Peers must be of the same switch series, along with

any expansion modules that may be used in the MLAG Peer-Link setup. There are also six areas in the

software configuration that must be given special attention to ensure they contain identical information

prior to enabling the MLAG. These areas are reflected in Figure 2.

MLAG peerpeer

linkMLAG peer

Link Aggregation

MLAG Port-channels

Interfaces

VLANs

Firmware

Spanning Tree

Link Aggregation

MLAG Port-channels

Interfaces

VLANs

Firmware

Spanning Tree

=

=

=

=

==

Consistent MLAG Peer configurations

http://en.community.dell.com/techcenter/networking/p/guides#N-series







When changing settings in any of the areas listed below in Table 1, it is required that the settings be

modified on both MLAG Peer switches. Enable MLAG only after configuring the settings on both Peer

switches. Failure to make these areas identical may cause sporadic traffic issues on the network which are

difficult to troubleshoot.

It is recommended that MLAG be temporarily disabled when making changes to these settings.

Caution: Failure to make these settings identical on both Peers may cause sporadic traffic issues on the

network which can be difficult to troubleshoot.

Note: Be sure to schedule down time if making changes that may impact traffic or cause data loss.

Option category Settings that need to match on both MLAG Peers

Link Aggregation Hashing mode

Minimum linksStatic/dynamic LAG

LACP parameters

o

Actor parameterso Admin key

o Collector max-delayo Partner parameters

Spanning Tree Bpdufilter

Bpduflood

Auto-edgeTCN-guard

CostEdgeport

Root guardLoop guard

STP Version

STP MST VLAN configuration

STP MST instance configuration (instance ID,port priority, port cost/mode)

MLAG Port-channels Port-channel modeLink speed

Duplex modeMTU

Bandwidth

VLAN configuration

Interfaces PFC configurationCoS queue assignments

VLANs MLAG VLANs must be configured on both

MLAG Peers, and connect to two Partner LAGs.

Firmware Both Peers require the same firmware version

to operate correctly.

Misc. FDB entry aging timersStatic MAC entriesACL configuration

Table 1 Settings required to match between MLAG Peers




3 Supported TopologiesMLAG topologies offer several options. They can be a single layer (only one pair of MLAG Peer switches) or

two layers (two pair of MLAG Peer switches). The Peer-Link between Peers can have anywhere from 1 to 8

active interfaces to create the link. With these and other variables, there are dozens of ways to setup an

MLAG. 0 lists all supported topology options.

Topological parameter Supported options

# of MLAG domains per switch 1

# of Peer switches per MLAG domain 2

# of interfaces per MLAG 2 to 8

# of interfaces per Peer-Link 1 to 8

# of MLAGs connecting to MLAG domain Limited only by number of ports available

# of layers 1 or 2

Table 2 Parameters for an MLAG topology

Figure 3 shows just a few examples of MLAG topologies that can be built using the MLAG feature. The red

lines show the Peer-Links between the primary and secondary Peer switches. The blue line in the bottom

diagram shows compatibility with VLT in a 2-layer topology. VLT is a technology similar to MLAG that is

used with certain Dell switches like the S4810. See the User Guide for the S4810 and other Dell switches

that use VLT for guidance on implementing a VLT.

full mesh

1 partner switch 3 partner switches

VLTi

2 partner switches

MLAG and VLT

QSFP+

M A S TE R

S Y S F AN P SU

R S -232

ETHERNETLNK A CT

4644424038363432302826242220181614121086420 48 56

5 2 6 0

SFP+

Fo rce10 S 4810P

QSFP+

M A S T ER

S Y S F A N P S U

R S -232

ETHERNETLNK A CT

4644424038363432302826242220181614121086420 48 56

52 60

SFP+

Fo rce10 S 4810P

full mesh

Examples of MLAG topologies




4 Single-Tier ExampleFigure 4 shows the configuration of the two MLAG Peers with two MLAG Partners. The default spanning

tree configuration is used and spanning tree is disabled on the Peer-Link.

MLAG

Secondary MLAG peerPeer-LinkPrimary MLAG peer

Partner Switch BPartner Switch A

N3048 N3048

(47)

(48)

(11)

(12)

(1/0/1)

(1/0/1)

(30)

(29)

(28)

(27)

MLAG

Single-tier MLAG topology

To configure the two MLAG Peers in the basic configuration, follow the steps below:

1. Enter the following commands on both Peer switches before enabling MLAG (using the feature vpc

command) on each one. Each configuration is also attached in the left “attachment” column (click the

paperclip icon) that can be used to cut and paste into a CLI session.

Primary MLAG Peer (N3048) Secondary MLAG Peer (N3048) Description of commandsconfigurevlan 30

exit

interface port-channel 1

description "MLAG-Peer-Link"switchport mode trunk

vpc peer-link

exit

interface tengigabitethernet 1/0/1channel-group 1 mode active

description "MLAG-Peer-Link"

exit


switchport mode trunk

vpc 30exit

configurevlan 30

exit



vpc peer-link

exit



exit



vpc 30exit

Create a VLAN for MLAG and all

Partner traffic

Configure the port channel for

the Peer-Link

- must be trunk mode

Identify and configure the

Peer-Link interface

-Peer-Link requires a native

VLAN (i.e. VLAN 1 or otherVLAN made native)

Create a LAG for Partner switch

A to pass traffic

Assign a unique id for Partner

switch A






vpc 40exit

interface gigabitethernet 1/0/47

channel-group 30 mode active

description "MLAG-Partner-link"exit


channel-group 40 mode activedescription "MLAG-Partner-Link"

exit

feature vpc

vpc domain 1

peer-keepalive enableexit



vpc 40exit



description "MLAG-Partner-Link"exit



exit

feature vpc

vpc domain 1


Create a LAG (port-channel) for

Partner switch B to pass traffic


switch B

Assign interfaces to connect to

Partner A LAG (channel-group)

Assign interfaces to connect to

Partner B LAG (channel-group)

Enable the MLAG

Partner Switch A Partner Switch B Description of commandsconfigurevlan 30

exit

interface port-channel 1switchport mode trunk

exit

interface gi1/0/27

channel-group 1 mode activeexit

interface gi1/0/28channel-group 1 mode active

exit

interface range gi1/0/xx-yy

switchport mode accessswitchport access vlan 30

exit

configurevlan 30

exit


exit

interface gi1/0/29



exit

interface range gi1/0/xx-yy

switchport mode accessswitchport access vlan 30

exit

create same VLAN on Partners

configure the port channel

trunk for the Partner link

Assign interfaces to MLAG

(channel-group)

Assign interfaces to MLAG

(channel-group)

Assign additional ports to the

VLAN only for hosts that will be

using the MLAG

The Peer-Link requires a native VLAN to be configured. It can use VLAN 1 (the default native VLAN) or

another VLAN that has been set to native. This is a limitation of the Peer-Link keep alive protocol.

Interfaces used to connect each Peer to the Partner switch LAG do not need to match on each Peer.

For instance, in the example above, one Partner LAG interface connects to 1/0/47 on the primary Peer

while the other interface connects to 1/0/11 on the secondary Peer.

2. Connect all cables as shown in Figure 4, or use the checklist in Error! Reference source not found..




Primary MLAG Peer

From Switch / Port To Switch / Port

☐ Primary MLAG Peer / 1/0/1 Secondary MLAG Peer / 1/0/1

☐ Primary MLAG Peer / 1/0/47 Partner Switch A / 1/0/27

☐ Primary MLAG Peer / 1/0/48 Partner Switch B / 1/0/30

Secondary MLAG Peer


☐ Secondary MLAG Peer / 1/0/11 Partner Switch A / 1/0/28

☐ Secondary MLAG Peer / 1/0/12 Partner Switch B / 1/0/29

Table 3 Cabling checklist for the single tier example

3. Run the show vpc brief command on either MLAG Peer to to display all information for both Peers.

Primary MLAG Peer Secondary MLAG Peer

show vpc brief

VPC domain ID.................................... 1

VPC admin status............................... EnabledKeep-alive admin status................... Enabled

VPC operational status..................... Enabled

Self role................................................ PrimaryPeer role.............................................. Secondary

Peer detection admin status........... DisabledOperational VPC MAC...................... ECF4.BBF5.2502

Operational VPC system priority…. 32767

Peer-Link details

-----------------Interface.................................................. Po1

Peer-link admin status......................... EnabledPeer-link STP admin status................. Disabled

Configured VLANs................................. 1,30

Egress tagged VLANs............................ 30

VPC Details-----------

Number of VPCs configured...................... 2

Number of VPCs operational..................... 2

VPC id# 30

-----------Interface.................................................... Po30

Configured VLANs.................................. 1,30VPC interface state................................. Active

show vpc brief

VPC domain ID........................................ 1

VPC admin status................................... EnabledKeep-alive admin status....................... Enabled

VPC operational status......................... Enabled

Self role........ ................. ............. ............ SecondaryPeer role...... ............... ............... ............ Primary

Peer detection admin status............... DisabledOperational VPC MAC.......................... ECF4.BBF5.2502

Operational VPC system priority…….. 32767

Peer-Link details

-----------------Interface.................................................. Po1


Configured VLANs................................. 1,30


VPC Details-----------

Number of VPCs configured...................... 2

Number of VPCs operational..................... 2

VPC id# 30

-----------Interface.................................................... Po30

Configured VLANs.................................. 1,30VPC interface state................................. Active




Local Members Status

----------------- ------

Gi1/0/47 Up

Peer Members Status---------------- ------

Gi1/0/11 Up

VPC id# 40

-----------Interface.............................................. Po40

Configured VLANs............................ 1,30VPC interface state........................... Active

Local Members Status----------------- ------

Gi1/0/48 Up

Peer Members Status

---------------- ------Gi1/0/12 Up


----------------- ------

Gi1/0/11 Up


Gi1/0/47 Up

VPC id# 40

-----------Interface............................................ Po40

Configured VLANs.......................... 1,30VPC interface state......................... Active


Gi1/0/12 Up

Peer Members Status

---------------- ------Gi1/0/48 Up

Results of the command should be the same as shown above. All member ports must show UP, and the

VPC interface state must show Active. When Partner switches are correctly configured with MLAGs and

connected to the MLAG Peers, the Number of VPCs operational in the show vpc brief command will

show 1 or more. A value of 0 indicates the Partner switches are not properly configured.

The show interface port-channel is another helpful tool to verify if the configured LAG ports are up and

running. This command can be run on both the primary and secondary Peers on a single layer MLAG

topology. If correctly configured, the port(s) in the LAG are listed with an Active status. If there are any

inactive ports, check for cabling or configuration issues.

Single-tier MLAG Peer show interface port-channel 40Channel Ports Ch-Type Hash Type Min-links Local Prf

------- ----------------------------- -------- --------- --------- ----

Po40 Active: Gi1/0/48 Dynamic 7 1 Disabled

Hash Algorithm Type1 - Source MAC, VLAN, EtherType, source module and port Id

2 - Destination MAC, VLAN, EtherType, source module and port Id

3 - Source IP and source TCP/UDP port4 - Destination IP and destination TCP/UDP port

5 - Source/Destination MAC, VLAN, EtherType, source MODID/port6 - Source/Destination IP and source/destination TCP/UDP port

7 - Enhanced hashing mode






In a full mesh, all eight ports joined together in the MLAG (four blue cables) are in the same port channel

to achieve maximum redundancy.

To configure the two-tier in a full mesh configuration, follow the steps below:

1. Enter the commands below for each corresponding switch in the topology.

2.

Cable the configuration as shown in Figure 6 or use the checklist in Table 4.

3. Enable MLAG (using the feature vpc command) on each switch.

Similar commands are performed on all four MLAG Peer switches. MLAG Peers B and C are required to be

consistent in their configurations following the guidelines set above in the Consistency of MLAG

Peers section. MLAG Peers D and E also follow consistency requirements. Though MLAG Partner switches

A and F may have similar configurations in this particular scenario, they have no such consistency

requirements to each other or to the Peer switches.

Each configuration below is also attached in the left “attachment” column (click the paperclip icon) that

can be used to cut and paste into a CLI session. Command sections are color-coded for easier reading.

MLAG Peer B MLAG Peer C Description of commands

configurevlan 30

exit



vpc peer-link

exit

interface tengigabitethernet 1/0/1

channel-group 1 mode activedescription "MLAG-Peer-Link"

exit

interface port-channel 40switchport mode trunkvpc 40

exit


vpc 50

exit

interface gigabitethernet 1/0/1channel-group 40 mode activedescription "MLAG-Partner-Link"

exit



exit

configurevlan 30

exit



vpc peer-link

exit

interface tengigabitethernet 1/0/1

channel-group 1 mode activedescription "MLAG-Peer-Link"

exit

interface port-channel 40switchport mode trunkvpc 40

exit


vpc 50

exit

interface gigabitethernet 1/0/1channel-group 40 mode activedescription "MLAG-Partner-Link"

exit



exit

Create a VLAN for MLAG and

all Partner traffic


the BC peer link


Identify and configure the BC

peer link interfaces

Create a LAG (port-channel)

for Partner switch DE to pass

traffic



for Partner switch A to pass

traffic


Assign interfaces to connectto Partner E ’s half of full mesh

LAG

Assign interfaces to connect

to Partner D ’s half of full mesh

LAG





channel-group 50 mode activeswitchport mode trunk

switchport trunk allowed vlan 30exit

feature vpcvpc domain 1



channel-group 50 mode activeswitchport mode trunk

switchport trunk allowed vlan 30exit

feature vpcvpc domain 1


Assign interfaces to VLAN that

will connect to Partner A’s LAG

-put both 13 and 14 into same

LAG 50

Enable the MLAG BC and DE must be in

separate domains

MLAG Peer D MLAG Peer E Description of commands

configure

vlan 30

exit



vpc peer-linkexit


description "MLAG-Peer-Link"exit


vpc 40exit


vpc 60exit

interface gigabitethernet 1/0/1channel-group 40 mode active





switchport mode trunkswitchport trunk allowed vlan 30

description "MLAG-Partner-Link"

exit

feature vpc

configure

vlan 30

exit



vpc peer-linkexit


description "MLAG-Peer-Link"exit


vpc 40exit


vpc 60exit






switchport mode trunkswitchport trunk allowed vlan 30


exit

feature vpc


all Partner traffic


the DE peer link


Identify and configure the DE



for Partner switch BC to pass

traffic


Create a LAG (port-channel)for Partner switch F to pass traffic



to Partner B ‘s half of full mesh

MLAG


to Partner C ‘s half of full mesh

LAG


will connect to Partner F ’s LAG

-put both 13 and 14 into same

LAG 60

Enable the MLAG




vpc domain 2

peer-keepalive enable

exit

vpc domain 2

peer-keepalive enable

exit

BC and DE must be in

separate domains

Partner Switch A Partner Switch F Description of commandsconfigure

vlan 30exit



exit


exit

interface gi1/0/14


exit

interface gi1/0/23switchport mode accessswitchport access vlan 30

exit

configure

vlan 30exit



exit


exit

interface gi1/0/14


exit

interface gi1/0/24switchport mode accessswitchport access vlan 30

exit



trunks for the Partner links

Assign first interface to LAG

(channel-group)

Assign second interface to

LAG (channel-group)



using the MLAG

Connect all cables as shown in Figure 6 on page 13 or use the checklist below in Table 4. Port 23 in switch

A connects to the Server, and port 24 in switch F connects to the PC client.

Note: Peers B and C are in their own MLAG domain. Peers D and E are also in their own MLAG

domain. Each domain views the other as a partner.

MLAG Peer A


☐ MLAG Partner A 1/0/13 MLAG Peer C 1/0/13

☐ MLAG Partner A 1/0/14 MLAG Peer B 1/0/14

MLAG Peer B


☐ MLAG Peer B Te/0/1 MLAG Peer C Te/0/1

☐ MLAG Peer B 1/0/1 MLAG Peer E 1/0/1

☐

MLAG Peer B 1/0/2 MLAG Peer D 1/0/1




MLAG Peer C


☐

MLAG Peer C 1/0/1 MLAG Peer E 1/0/2

☐

MLAG Peer C 1/0/2 MLAG Peer D 1/0/2

MLAG Peer D


☐

MLAG Peer D / Te0/1 MLAG Peer E / Te0/1

☐

MLAG Peer D / 1/0/14 MLAG Partner F / 1/0/14

MLAG Peer E


☐

MLAG Peer E / 1/0/13 MLAG Partner F / 1/0/13

Table 4 Cabling checklist for the two-tier example

4. Run the show vpc brief command on either MLAG Peer to display information for both Peers.

Note: Interfaces used to connect each Peer to the Partner switch LAG are not required to match on each

Peer. For instance, in the example above, one Partner LAG interface connects to 1/0/47 on the primary

Peer while the other interface connects to 1/0/11 on the secondary Peer. It is not required that both

Peers use port 1/0/47 or port 1/0/11.

Note: The Partner switches must be configured with LAGs and be connected to the MLAG Peers, or the

“Number of VPCs operational” in the show vpc brief command will show 0.

MLAG Peer B (Primary Peer) MLAG Peer C (Secondary Peer)show vpc brief

VPC domain ID...................................... 1VPC admin status............................... Enabled

Keep-alive admin status................... EnabledVPC operational status..................... Enabled

Self role................................................ Primary

Peer role.............................................. SecondaryPeer detection admin status........... Disabled

Operational VPC MAC...................... ECF4.BBF6.2512


Peer-Link details-----------------

Interface.................................................. Po1


Configured VLANs................................ 1,30Egress tagged VLANs............................ 30

show vpc brief

VPC domain ID...................................... 1VPC admin status............................... Enabled

Keep-alive admin status................... EnabledVPC operational status..................... Enabled

Self role................................................ Secondary

Peer role.............................................. PrimaryPeer detection admin status........... Disabled

Operational VPC MAC...................... ECF4.BBF6.2512


Peer-Link details-----------------

Interface.................................................. Po1


Configured VLANs................................. 1,30Egress tagged VLANs............................ 30




VPC Details

-----------

Number of VPCs configured...................... 2Number of VPCs operational..................... 2

VPC id# 40

-----------

Interface................................................ Po40Configured VLANs............................... 1,30

VPC interface state............................. Active


Gi1/0/1 Up

Gi1/0/2 Up

Peer Members Status

---------------- ------Gi1/0/1 Up

Gi1/0/2 Up

VPC id# 50-----------

Interface................................................ Po50

Configured VLANs............................... 1,30VPC interface state............................. Active


----------------- ------Gi1/0/14 Up


Gi1/0/13 Up

VPC Details

-----------

Number of VPCs configured...................... 2Number of VPCs operational..................... 2

VPC id# 40

-----------

Interface................................................ Po40Configured VLANs............................... 1,30



Gi1/0/1 Up

Gi1/0/2 Up

Peer Members Status

---------------- ------Gi1/0/1 Up

Gi1/0/2 Up

VPC id# 50-----------

Interface................................................ Po50

Configured VLANs............................... 1,30VPC interface state............................. Active


----------------- ------

Gi1/0/13 Up


Gi1/0/14 Up

All member ports must show UP, and the VPC interface state must show Active.

The show interface port-channel is another helpful tool to let you know if the configured LAGs are up and

running. When correctly configured, ports in the LAG are listed with an Active status. Inactive ports are

usually a sign of a cabling or configuration issue.

MLAG Peersshow interface port-channel 40

Channel Ports Ch-Type Hash Type Min-links Local Prf

------- ----------------------------- -------- --------- --------- ----

Po40 Active: Gi1/0/1, Gi1/0/2 Dynamic 7 1 Disabled

Hash Algorithm Type

1 - Source MAC, VLAN, EtherType, source module and port Id2 - Destination MAC, VLAN, EtherType, source module and port Id

3 - Source IP and source TCP/UDP port4 - Destination IP and destination TCP/UDP port

5 - Source/Destination MAC, VLAN, EtherType, source MODID/port

6 - Source/Destination IP and source/destination TCP/UDP port7 - Enhanced hashing mode




6 Connecting Single-homed PartnersSingle-homing a device by attaching it to only one Peer does not actually create an MLAG “Partner.”

When configuring an MLAG topology, Partner devices (switches, servers, storage, or other) must use an

MLAG link aggregation that spans both MLAG Peers in order to be a Partner. Using only one cable or port-

channel going into only one of the MLAG Peers (Figure 7) does not take advantage of the multiple path

MLAG and can lead to data loss.

MLAG peerPeer-Link

MLAG peer

X X

Device A

Device B

Unsupported single-homed Partner devices

Traffic to and from non-redundant ports is filtered and never crosses the MLAG Peer-Link. Such

ports/VLANs need to obtain connectivity via an alternative to the MLAG-connected ports/VLANs. There are

three ways to circumvent the problem of a singled-homed device that allows it to attach and pass traffic

through the MLAG topology.

Solution 1

The first solution, as shown in Figure 8, shows single-homed devices attaching to only one MLAG Peer.An extra port-channel connection between the MLAG Peers allows for non-MLAG VLAN traffic from the

single-homed devices to cross from one Peer to the other. This can only be run in an MSTP environment

and is not supported when running RSTP. For this example, VLANs 1-39 are used in the MLAG, with VLAN

40 dedicated to be used only by devices with non-redundant links. No MLAG benefits are achieved for

these attached devices when using this method.

MLAG peerPeer-Link

MLAG

MLAG peer

PartnerDevice

Device

VLAN 40

VLAN 40VLAN 40 VLAN 40

VLANs 1-39

MSTP

Environment

Solution 1 - Adding a VLAN link between the MLAG Peers




MLAG interfaces and non-redundant ports cannot be members of the same VLAN, i.e. a VLAN may contain

MLAG interfaces or a VLAN may contain non-redundant ports, but not both.

Note: Solution 1 can be ran in an MSTP environment only. The MSTP domain should always be named

in order for the peer-link to remain unblocked.

Solution 2As shown in Figure 9, the second solution is to configure one or more MLAG Partner switches between

the MLAG Peers and the devices that require a single link. The single-homed devices (e.g. A, B, C, and D)

can then pass traffic across the MLAG domain.

M L A GM L A G

MLAG peerPeer-Link

MLAG peer

Partner Y Partner ZConnecting single-homed

devices to Partner devices

already configured for MLAG

Device A Device CDevice B Device D

Solution 2 - Connecting devices to a Partner switch

Solution 3A third solution, as shown in Figure 10, is achieved through multi-homing the Partner device, and thereby

creating an MLAG. By adding one or more cables to the device, creating a LAG, and splitting the LAG with

half of the cables going to one MLAG Peer, and half going to the other MLAG Peer, the redundant multi-

path advantage is attained. Attaching to a minimum of two Partner devices is mandatory in order to take

advantage of MLAG.

M L A G

M L A G

MLAG peerPeer-Link

MLAG peer

Partner A

Partner B

Solution 3 – Muli-homed, Multi-switch LAG (MLAG)




Explaining the MLAG method (solution 3) is the primary purpose of this guide, and a complete explanation

including N-Series switch configurations for this topology are found in the

Single-Tier Example on page 9. To configure link aggregation for servers, storage, or other devices,

consult the User Guides for the NICs being used in those devices.




7 MLAG with VLTMLAG can also be used in combination with Virtual Link Trunking (VLT). VLT is the technology similar to

MLAG that can be implemented on certain Dell switches like the S4810. Figure 11 shows MLAG Peers on

one layer and VLT Peers on the second layer, with a full-mesh LAG. The orange line shows the VLTi (VLT

interconnect) for the VLT domain and the red line shows the Peer-Link for the MLAG domain. The top and

bottom partner switches (labeled A and F ) may be any switch model.

Peer-Link

MLAG

VLTiS4810 S4810

LAG

LAG

B. C.

D. E.

F.

A.

full mesh

N4032 N4032

QSFP+

M A S T E

R

S Y S

F A N

P S U

RS-232

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52 60

SFP+

Force10 S4810P

QSFP+

M A S T E

R

S Y S

F A N

P S U

RS-232

ETHERNETL NK A CT

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52 60

SFP+

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19 21 23

20 2 2 2 4

17

18

11 13 1 5

12 14 1 6

9

10

3 5 7

4 6 8

1

2

ACTLNK 19 21 23

20 22 24

17

18

1 1 1 3 15

1 2 1 4 16

9

10

3 5 7

4 6 8

1

2

ACTLNK

Mixed full-mesh LAG using MLAG and VLT

This topology is similar to the one shown in Figure 5 on page 13 but replaces B and C with S4810 switchesand D and E with N4032 switches in order to illustrate compatibility of VLT with MLAG protocols. This

particular scenario also provides a full-mesh 10 GbE solution. 40 GbE interfaces will be used for the VLTi

and Peer-Link connections.

Note: Other 10 GbE solutions include using all N4000 Series switches (MLAG only) or all S4810 switches

(VLT only) for “BCDE ”.

Figure 12 shows the physical layout of the same topology as it might appear in a rack, including cabling

and attached hosts that need to communicate across the MLAG/VLT. The same color scheme is used for

the cables in Figure 12 that was used to show logical connections in Figure 11.




Stack No.

1

2

1 2SFP+

3 5 7 9 11

4 6 8 10 1 2

13 15 17 19 21

14 16 18 2 0 22 24

L N K A C T1

2 COMBO P

23

L NK A CT

Stack No.

1

2

1 2SFP+

3 5 7 9 11

4 6 8 10 12

13 15 17 19 21

14 16 18 20 22 24

L N K A C T1

2 COMBO P

23

L NK A CT

Server

PC

A.

B.

C.

D.

E.

F.

(23)

(1-2)

(24)

(56)

(Fo 2)

(Te 1-2)

Ports are denoted bythe port # inparenthesis.

Example:port 1/0/23

is shown as (23)

QSFP+

M A S T E R

S Y S

F A N

P S U

RS-232

ETHERNETLNK ACT

4644424038363432302826242220181614121086420 48 56

52 60

SFP+

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QSFP+

M A S T E

R

S Y S

F A N

P S U

RS-232

ETHERNETLNK ACT

4644424038363432302826242220181614121086420 48 56

52 60

SFP+

Force10 S4810P

19 21 23

20 22 24

17

18

11 13 15

12 14 16

9

10

3 5 7

4 6 8

1

2

ACTLNK

19 21 23

20 22 24

17

18

11 13 15

12 14 16

9

10

3 5 7

4 6 8

1

2

ACTLNK

(Te 1-2)

QSFP MODULE

ACT

LNK

ACT

LNK

QSFP MODULE

ACT

LNK

ACT

LNK

(Fo 2)

(22-23)

(22-23)

(56)

(1-2)

(1-2)

= LAG

(47)

(47)

(24)

(24)

Physical cabling of a two-tier MLAG/VLT full-mesh configuration

The configurations below are used in configuring this example.

Note: In a full mesh of MLAG-only peer switches (as shown in the two-tier example in Figure 5), each

peer pair must be in it's own MLAG domain. However, with a full mesh of one MLAG peer pair and one

VLT peer pair, each pair is already in their own domain within its’ protocol. For this reason, both peer

pairs may use the same domain number if desired.

Enter the commands for each corresponding switch in the topology, then cable the configuration as

shown in the above figure.

Configurations are also attached in the left “attachment” column that can be used to cut and paste into a

CLI session. Click the paperclip icon to expose the list of attachments. Command sections are color-

coded for easier reading.

VLT Peer B (S4810) VLT Peer C (S4810) Description of commands

configure

protocol spanning-tree rstpno disable

interface vlan 30no shutdown

exit

interface port-channel 1description "VLT-Peer-Link"

no ip address

channel-member Fo 0/56no shutdown

configure

protocol spanning-tree rstpno disable

interface vlan 30no shutdown

exit

interface port-channel 1description "VLT-Peer-Link"

no ip address

channel-member Fo 0/56no shutdown

Enable spanning tree, which is

disabled by default on the S4810

Create one or more VLANs for

Partner traffic


the peer link

- can be different than DE

port channel

Assign the peer link interfaces




exit

interface forty 0/56no shutdown

exit

vlt domain 1

peer-link port-channel 1back-up destination 172.25.194.24

primary-priority 1system-mac mac-address

aa:bb:cc:dd:12:34unit-id 0

exit


no ip address

switchportrate-interval 30

vlt-peer-lag port-channel 40no shutdown

exit

interface Te 0/22

description “Link to MLAG" no ip address

port-channel-protocol LACPport-channel 40 mode active

no shutdown

exit

interface Te 0/23description “Link to MLAG"

no ip address

port-channel-protocol LACP

port-channel 40 mode activeno shutdown

exit

interface port-channel 50no ip address

switchport

rate-interval 30no shutdown

vlt-peer-lag port-channel 50exit

interface vlan 30

tagged port-channel 40,50

exit

interface Te 0/47

no ip addressport-channel-protocol LACP


exit

exit

exit

interface forty 0/56no shutdown

exit

vlt domain 1

peer-link port-channel 1back-up destination 172.25.194.25

primary-priority 2system-mac mac-address

aa:bb:cc:dd:12:34unit-id 1

exit


no ip address

switchportrate-interval 30

vlt-peer-lag port-channel 40no shutdown

exit

interface Te 0/22

description “Link to MLAG" no ip address

port-channel-protocol LACPport-channel 40 mode active

no shutdown

exit

interface Te 0/23description “Link to MLAG"

no ip address

port-channel-protocol LACP


exit

interface port-channel 50no ip address

switchport

rate-interval 30no shutdown

vlt-peer-lag port-channel 50exit

interface vlan 30

tagged port-channel 40,50

exit

interface Te 0/47

no ip addressport-channel-protocol LACP


exit

exit

Bring up the peer interfaces

Setup the VLT domain

-identify a port channel-provide the management

address of the other peer-lower priority will be primary

-provide a MAC for the pair-provide correct unit-id (0-1)


for Partner switch DE

-put into L2 mode

-set rate interval

-port channel of peer (same

here for ease of remembering)


to Partner D ’s half of full mesh

LAG


to Partner E ’s half of full mesh

LAG


for Partner switch A to pass

traffic

-put into L2 mode

-set rate interval

-port channel of peer (same

here for ease of remembering

Add the port-channels to

VLAN 30


will connect to Partner A’s LAG

-put both into same LAG 50




MLAG Peer D (N4032F) MLAG Peer E (N4032F) Description of commands

configurevlan 30

exit



vpc peer-link

exit

interface forty 1/1/2channel-group 1 mode active


exit


switchport mode trunkvpc 40

exit

interface ten 1/0/1channel-group 40 mode active


exit



exit


vpc 60

exit

interface ten 1/0/24channel-group 60 mode activeswitchport mode trunk


feature vpc

vpc domain 2

peer-keepalive enableexi

exit

configurevlan 30

exit



vpc peer-link

exit

interface forty 1/1/2channel-group 1 mode active


exit


switchport mode trunkvpc 40

exit



exit



exit


vpc 60

exit

interface ten 1/0/24channel-group 60 mode activeswitchport mode trunk


feature vpc

vpc domain 2


exit


all Partner traffic


the DE peer link- must be trunk mode

Identify and configure the DE



for Partner switch BC traffic


switch BC


to B ‘s half of full mesh LAG


to C ‘s half of full mesh LAG


for Partner switch F to pass traffic


switch F

Assign interfaces to VLAN thatwill connect to Partner F’s LAG

-put both into same LAG 60

Enable the MLAG

Partner Switch A Partner Switch F Description of commandsconfigurevlan 30

exit


switchport mode trunkexit

configurevlan 30

exit


switchport mode trunkexit



trunks for the Partner links




interface te1/0/1


interface te1/0/2


exit

interface gi1/0/23switchport mode access

switchport access vlan 30exit

exit

interface te1/0/1


interface te1/0/2


exit

interface gi1/0/24switchport mode access

switchport access vlan 30exit

exit

Assign first interface to LAG

(channel-group)

Assign second interface to

LAG (channel-group)



using the MLAG

Connect all cables as shown in Figure 12 on page 23 or use the checklist below in Table 5. Port 23 in

switch A connects to the Server, and port 24 in switch F connects to the PC client.

Partner Switch A


☐ Partner Switch A / Te0/1 VLT Peer B / 1/0/47

☐ Partner Switch A / Te0/2 VLT Peer C / 1/0/47

VLT Peer B


☐ VLT Peer B / 1/0/56 VLT Peer C / 1/0/56

☐ VLT Peer B / 1/0/22 MLAG Peer E / 1/0/1

☐

VLT Peer B / 1/0/23 MLAG Peer D / 1/0/1

VLT Peer C


☐

VLT Peer C / 1/0/23 MLAG Peer E / 1/0/2

☐

VLT Peer C / 1/0/22 MLAG Peer D / 1/0/2

MLAG Peer D


☐

MLAG Peer D / Fo0/2 MLAG Peer E / Fo0/2

☐

MLAG Peer D / 1/0/24 Partner Switch F / Te0/2




MLAG Peer E


☐

MLAG Peer E / 1/0/24 Partner Switch F / Te0/1

Table 5

Cabling checklist for the MLAG with VLT example

Run the show vpc brief command on one of the MLAG Peers to display information for the MLAG Peers.

Note: Interfaces used to connect each Peer to the Partner switch LAG are not required to match on each

Peer. For instance, in the example above, one Partner LAG interface connects to 1/0/47 on the primary

Peer while the other interface connects to 1/0/11 on the secondary Peer. It is not required that both

Peers use port 1/0/47 or port 1/0/11.

Note: The Partner switches must be configured with LAGs and be connected to the MLAG Peers, or the

“Number of VPCs operational” in the show vlt brief command will show 0.

MLAG Peer D (N4032F) MLAG Peer E (N4032F)

show vpc brief

VPC domain ID........................................ 2

VPC admin status................................... Enabled

Keep-alive admin status....................... EnabledVPC operational status......................... Enabled

Self role.................................................... PrimaryPeer role.................................................. Secondary

Peer detection admin status............... DisabledOperational VPC MAC.................... ECF4.BBF4.2402Operational VPC system priority........ 32767

Peer-Link details

-----------------

Interface.................................................. Po1Peer-link admin status......................... Enabled

Peer-link STP admin status................. EnabledConfigured VLANs................................. 1,30


VPC Details

-----------

Number of VPCs configured................. 2Number of VPCs operational................ 2

VPC id# 40

-----------Interface................................................ Po40

Configured VLANs............................... 1,30


show vpc brief

VPC domain ID........................................ 2

VPC admin status................................... Enabled

Keep-alive admin status....................... EnabledVPC operational status......................... Enabled

Self role.................................................... SecondaryPeer role.................................................. Primary

Peer detection admin status............... DisabledOperational VPC MAC........................ ECF4.BBF4.2402Operational VPC system priority........ 32767

Peer-Link details

-----------------

Interface.................................................. Po1Peer-link admin status......................... Enabled

Peer-link STP admin status................. EnabledConfigured VLANs................................. 1,30


VPC Details

-----------

Number of VPCs configured................. 2Number of VPCs operational................ 2

VPC id# 40

-----------Interface................................................ Po40







----------------- ------

Te1/0/1 UpTe1/0/2 Up

Peer Members Status

---------------- ------


VPC id# 60

-----------Interface................................................ Po60




----------------- ------Te1/0/24 Up

Peer Members Status

---------------- ------Te1/0/24 Up


----------------- ------


Peer Members Status

---------------- ------


VPC id# 60

-----------Interface................................................ Po60




----------------- ------Te1/0/24 Up

Peer Members Status

---------------- ------Te1/0/24 Up

Results of the command should be the same as shown above. All member ports must show Up, and the

VPC interface state must show Active.

The show interface port-channel is another helpful tool to let you know if the configured LAGs are up and

running. If correctly configured, ports in the primary LAG are listed with an Active status. Inactive ports are

usually a sign of a cabling or configuration issue.

MLAG Peers

show interfaces port-channel 40

Channel Ports Ch-Type Hash Type Min-links Local Prf------- ----------------------------- -------- --------- --------- ---------

Po40 Active: Te1/0/1, Te1/0/2 Dynamic 7 1 Disabled

show interfaces port-channel 60

Channel Ports Ch-Type Hash Type Min-links Local Prf------- ----------------------------- -------- --------- --------- ---------

Po60 Active: Te1/0/24 Dynamic 7 1 Disabled

Run show vlt brief and other commands on one of the VLT Peers to display information for the VLT Peers.

ICL Link, Heartbeat, and VLT Peer Status should all show Up.




VLT Peer B (Primary Peer) VLT Peer C (Secondary Peer)

show vlt brief

VLT Domain Brief

------------------

Domain ID: 1Role: Primary

Role Priority: 1

ICL Link Status: Up

HeartBeat Status: Up

VLT Peer Status: Up

Local Unit Id: 0

Version: 6(4)

Local System MAC address:

00:01:e8:8b:36:0e

Remote System MAC address:

00:01:e8:8b:3b:6f

Configured System MAC address:

aa:bb:cc:dd:12:34Remote system version: 6(4)

Delay-Restore timer: 90 seconds

Delay-Restore Abort Threshold: 60 seconds

Peer-Routing : Disabled

Peer-Routing-Timeout timer: 0 seconds

Multicast peer-routing timeout: 150 seconds

show vlt detail

Local LAG Id Peer LAG Id Local Peer VLANs-------------- --------------- ------- ------- ---------

40 40 UP UP 3050 50 UP UP 30

show running-config vlt

vlt domain 1

peer-link port-channel 1

back-up destination 172.25.194.24

primary-priority 1

system-mac mac-address aa:bb:cc:dd:12:34

unit-id 0

show vlt backup-link

VLT Backup Link

-----------------

Destination: 172.25.194.24

Peer HeartBeat status: Up

Destination VRF: default

HeartBeat Timer Interval: 1

show vlt brief

VLT Domain Brief

------------------

Domain ID: 1Role: Secondary

Role Priority: 2

ICL Link Status: Up

HeartBeat Status: Up

VLT Peer Status: Up

Local Unit Id: 1

Version: 6(4)

Local System MAC address:

00:01:e8:8b:3b:6f

Remote System MAC address:

00:01:e8:8b:36:0e

Configured System MAC address:

aa:bb:cc:dd:12:34Remote system version: 6(4)

Delay-Restore timer: 90 seconds

Delay-Restore Abort Threshold: 60 seconds

Peer-Routing : Disabled

Peer-Routing-Timeout timer: 0 seconds

Multicast peer-routing timeout: 150 seconds

show vlt detail

Local LAG Id Peer LAG Id Local Peer VLANs-------------- --------------- ------- ------- ---------

40 40 UP UP 3050 50 UP UP 30

show running-config vlt

vlt domain 1

peer-link port-channel 1

back-up destination 172.25.194.25

primary-priority 2

system-mac mac-address aa:bb:cc:dd:12:34

unit-id 0

show vlt backup-link

VLT Backup Link

-----------------

Destination: 172.25.194.25

Peer HeartBeat status: Up

Destination VRF: default

HeartBeat Timer Interval: 1




HeartBeat Timeout: 3

UDP Port: 34998

HeartBeat Messages Sent: 257900

HeartBeat Messages Received: 257868

HeartBeat Timeout: 3

UDP Port: 34998

HeartBeat Messages Sent: 257877

HeartBeat Messages Received: 257879

Results of the command should be in proximity to those above. The Destination should show the

management IP address of the peer switch, and the Peer HeartBeat status should be Up.

Consult the S4810 User Guide or VLT Deployment Guide for additional information on implementing VLT.

http://en.community.dell.com/techcenter/networking/p/guides#S-series



http://en.community.dell.com/techcenter/networking/m/networking_files/20440794








8 Additional ResourcesSupport.dell.com is focused on meeting your needs with proven services and support.

DellTechCenter.com is an IT Community where you can connect with Dell Customers and Dell

employees for the purpose of sharing knowledge, best practices, and information about Dell products and

installations.

Referenced or recommended Dell publications:

Dell Networking Support

- http://www.dell.com/support

Dell TechCenter (community forums and blogs for Dell customers)

- http://delltechcenter.com

Dell Networking Whitepapers

-

http://en.community.dell.com/techcenter/networking/p/guides

Dell Networking N2000/N3000/N4000 User Guides and Firmware downloads

- http://en.community.dell.com/techcenter/networking/p/guides#N-series

Configuration Details

This paper was compiled using the following components and versions.

Component Revision

Dell N2000, N3000, N4000 6.2.0.3

Dell S4810 Dell Application Software (Firmware) Version 9.6

http://www.dell.com/support

http://delltechcenter.com/


















Appendix

Unsupported Configurations

The configurations and topologies found in this guide are supported. A few configuration models that are

not supported are discussed below.

Using different types of expansion modules in a Peer-Link is not supported. Peer devices must use the

same type of expansion module if ports from the expansion modules are to be part of the MLAG interface.

Stacking of either MLAG peer is not supported. Neither switch used as MLAG Peers may be stacked with

other switches.

Using two different series switch models as MLAG peers is not supported. Same series switch models are

required to create MLAG Peers. This means any N2000 Series can only be peered with another N2000

Series, an N3000 Series with another N3000 Series, and an N4000 Series with another N4000 Series.

Figure 13 shows another example of an unsupported configuration, attempting to connect an MLAG Peer

with a non-MLAG Peer, such as a VLTi (shown) or Cisco vPC/VSS Peer. These type of “mixed protocol”

scenarios are not supported with MLAG.

N3048

Peer-Link

LAG

VLTi

S4810QSFP+

M A S T E R

S Y S F A N P S U

RS-232

ETHERNETL N K A CT

4644424038363432302826242220181614121086420 48 56

5 2 6 0

SFP+

Force10 S4810P

X

Unsupported Peer configuration



Support and Feedback

Contacting Technical Support

Support Contact Information Web: http://Support.Dell.com/

Telephone: USA: 1-800-945-3355

Feedback for this document

We encourage readers of this publication to provide feedback on the quality and usefulness of this

document by sending an email to Using MLAG in Dell Networks Feedback

About Dell

Dell is a worldwide leader in data center and campus solutions which includes the manufacturing and

distribution of servers, network switches, storage devices, personal computers, and related hardware and

software. For more information on these and other products, please visit the Dell website at

http://www.dell.com

http://support.dell.com/



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