Port aggregation

A.K. Gautam

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CCNP SWITCH

PORTABLE STUDY GUIDE

&

PRACTICE WORK BOOK

ANUJ KUMAR

email:- [email protected]

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networkbulls.com

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mailto:[email protected]

A.K. Gautam

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PORT AGGREGATION/ETHERCHANNEL

Spanning tree protocol only allows a single link between switch to switch because it prevents bridge loop.

Cisco Ether channel technology allows for the scaling of the link bandwidth by aggregating or bundling parallel links.

In Ether channel treats multiple line as a single link, logical link. The ether channel allows for two or eight links.

The Cisco catalyst family of switches supports two types of link aggregation.

PAgP (port aggregation protocol): - It is cisco proprietary protocol. It is default protocol, when we port channel

created.

LACP (link aggregation control protocol): - It is industy standard protocol. Its standard IEEE 802.3ad based protocol.

Etherchannel provide redundancy.

If one link fails traffic is automatically moved to another link.

Conditions:-

1. Both side same media type and speed.

2. Same duplex.

3. Same Vlan(If access)

4. Same trunking encapsulation and mode(if trunk)

5. Same native vlan.

Note: - Load is not balanced equally across links.

Etherchannel uses a hashing algorithm. Two inputs are used (Source IP address and Destination IP address)

How this work.

We will focus on the 2, 4, or 8 link because it is easier to understand for you.

A 2 link Etherchannel bundle require a 1 bit index using an XOR.

If the index is 0, link 0 is selected.

If the index is 1, link 1 is selected.

A 4 link Etherchannel bundle requires a 2 bit index using an XOR.

4 possible links: 00, 01, 10, 11

Let’s See

00 = link 0

01 = link 1

10 = link 2

11 = link 3

An 8 link etherchannel bundle requires a 3 bit index using an XOR.

8 possible links: 000, 001, 010, 011, 100, 101, 110, 111.

Same as:-

000 = link 0

001 = link 1

010 = link 2

011 = link 3

100 = link 4

101 = link 5

110 = link 6

111 = link 7

Note: - XOR (Exclusive OR), 0 value = false, 1 value = True. If boot bits have same value (both 0, both 1), the XOR will

result in a 0. Otherwise, if these value are different (one is a 0 and other is a 1), the result will be 1.

A.K. Gautam

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Example: 2 Link

EtherChannel.

Packet sent from 172.16.1.1 to 10.10.10.16. The chosen hash uses Source IP (172.16.1.1) and Destination IP

(10.10.10.16) address.

172.16.1.1 => 00000001 (Source IP address)

10.10.10.16 => 00001000 (Destination IP address)

In our example we have 2 links in the EtherChannel (1 bit index):

The XOR is performed only one rightmost(right side) bit 1 XOR 0

1 XOR 0 = 1

Link 1 is used

Note: - XOR of the two bits result in 0, then link 0 is used. If XOR of the two bits result in 1, then link 1 is used.

Example: 4 Link EtherChannel.


(10.10.10.46) address.



In our example we have 4 links in the EtherChannel (2 bit index):

The XOR is performed only 2 rightmost (right side) bit 01 XOR 00

Each bit is computed separately

01 XOR 10 = 11

1 XOR 0 = 1

Link 0

Link 1

Link 3

Link 0

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0 XOR 1 = 1

According to link

0 XOR 0 = 0 link = 0

0 XOR 1 = 1 link = 1

1 XOR 0 = 1 link = 2

1 XOR 1 = 0 link = 3

Example: 4 Link EtherChannel


(10.10.10.46) address.



If there are 8 links in the EtherChannel (3 bit index):

The XOR is performed only on the 3 rightmost bits 001 XOR 110

Each bit is computed separately

001 XOR 110 = 111

1 XOR 0 = 1

0 XOR 1 = 1

0 XOR 1 = 1

According to link

8 possible links: 000, 001, 010, 011, 100, 101, 110, 111.

Same as:-

000 = link 0

001 = link 1

010 = link 2

011 = link 3

100 = link 4

101 = link 5

110 = link 6

111 = link 7

See more Information:-

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml

Link 0

Link 7

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml

A.K. Gautam

[email protected]

CONFIGURE ETHERCHANNEL LOAD BALANCING.

Load balancing configure on Global mode.

Switch(config)# port-channel load-balance method

Switch(config)# port-channel load-balance ?

dst-ip Dst IP Addr bits

dst-mac Dst Mac Addr bits

src-dst-ip Src XOR Dst IP Addr XOR

src-dst-mac Src XOR Dst Mac Addr XOR

src-ip Src IP Addr bits

src-mac Src Mac Addr bits

EtherChannel protocol

The Cisco Catalyst family of switches supports both:

Port Aggregation Protocol (PAgP) - Cisco proprietary (Default when port channel is created).

Link Aggregation Control Protocol (LACP) - Industry standard 802.3ad-based protocol (When a Cisco switch is

connected to a non-Cisco switch use LACP)

Note: - Must be same protocol on the both side. switch(config)# interface range fa 0/1 - 4

switch(config-if-range)# channel-protocol ?

lacp Prepare interface for LACP protocol

pagp Prepare interface for PAgP protocol

switch(config-if-range)# channel-protocol pagp

Channel-group number: 1 – 64

(Does not need to be the same on both switches but it’s recommended that it usually is)

switch(config)# interface range fa 0/1 - 4

switch(config-if-range)# channel-protocol ?

lacp Prepare interface for LACP protocol

pagp Prepare interface for PAgP protocol

On On

Desirable Auto

Active Passive

EthjerChannel

PAgP Negotiated EtherChannel

EtherChannel

LACP Negotiated EtherChannel

A.K. Gautam

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switch(config-if-range)# channel-group number mode {active | on | {auto [non-

silent]} | {desirable [non-silent]} | passive}

if No PAgP or LACP negotiation used

switch(config)# interface range fa 0/1 – 4

switch(config-if-range)# channel-protocol pagp

switch(config-if-range)# channel-group 1 mode on

active Enable LACP unconditionally

auto Enable PAgP only if a PAgP device is detected

desirable Enable PAgP unconditionally

on Enable Etherchannel only

passive Enable LACP only if a LACP device is detected

Note: - Both ends must be on

PAgP (Port Aggregation Protocol)

PAgP modes: -

1: -Desirable

2: -Auto

1:- in this mode switch sends a request to neighbor switch for either channel negotiation.

2:- in this mode a switch read for negotiation but it does not send a request to neighbor switch for either channel

negotiation.

Switch1(config)# interface range fa 0/1 – 4

Switch1(config-if-range)#switchport mode trunk

Switch1(config-if-range)# switchport trunk encapsulation dot1q

Switch1(config-if-range)# channel-protocol pagp

Switch1(config-if-range)# channel-group 1 mode desirable



Switch2(config-if-range)#switchport trunk encapsulation dot1q

Switch2(config-if-range)# channel-protocol pagp

Switch2(config-if-range)# channel-group 1 mode auto

Note: - Load balancing does not have to match.

switch1(config)# port-channel load-balance dst-ip

switch2(config)# port-channel load-balance src-dst-ip

Verifying: -

Switch#show etherchannel protocol

Switch#show etherchannel load-balance

Switch#show ehterchannel summary

Switch#show etherchannel port

A.K. Gautam

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LACP (Link Aggregation control Protocol)

LACP Modes: -

1: -Active:

2: -Passive:

1: - An interface in the active mode can negotiation an EtherChannel with another interface that is in the active or

passive mode.

2: - An interface in the passive mode cans negotiation an EtherChannel with another interface that is in the active

mode.

Note: - An interface in the passive mode cannot negotiation an EtherChannel with another interface that is also in

the passive mode because neither interface starts LACP negotiation.




Switch1(config-if-range)# channel-protocol lacp

Switch1(config-if-range)# channel-group 1 mode active





Switch2(config-if-range)# channel-group 1 mode passive

Port Priority

LACP uses the port priority to decide which port should be put in standby mode.

Ports with lower priority are active, and rest ports are standby (Default

32678).

For Example we use 4 links.





Switch1(config-if-range)# channel-group 1 mode active

Switch1(config-if-range)#lacp port-priority 99





Switch1(config-if-range)# channel-group 1 mode passive

Note: - Load balancing does not have to match.

switch1(config)# port-channel load-balance dst-ip

switch2(config)# port-channel load-balance src-dst-ip

Verifying: -

Switch#show etherchannel protocol

A.K. Gautam

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Switch#show etherchannel load-balance

Switch#show ehterchannel summary

Switch#show etherchannel port

Thanks giving me your precious time.

A.K. Gautam

Technology

Port aggregation