© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 1

Silent Host Connectivity Problem

• OTV assumes that there are no silent or unidirectional devices:http://www.cisco.com/en/US/docs/solutions/Enterprise/Data_Center/DCI/whitepaper/DCI_1.html#wp1185931

• There are several scenarios where a silent host can cause connectivity issues. The purpose of this document is to show why traffic loss occurs during an AED failover.

• Note that any type of broadcast/unicast flooded packet sourced from the silent host that reaches the AED will resolve the issue.

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 2

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Physical View

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

4948-210.0.0.102c84c.75f6.283f

4948-110.0.0.101c84c.75f6.013f

AED

AED

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 3

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

Host-210.0.0.102c84c.75f6.283f

Host-110.0.0.101c84c.75f6.013f

AED

AED

S1-OTV-2# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.013f 42 00:00:27 overlay S2-OTV-1 10 c84c.75f6.283f 1 00:01:36 site port-channel102

S2-OTV-1# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.013f 1 00:00:36 site Ethernet10/13 10 c84c.75f6.283f 42 00:01:44 overlay S1-OTV-2

Continuous pings to 4948-2

Silent Host Failover

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 4

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

Host-210.0.0.102c84c.75f6.283f

Host-110.0.0.101c84c.75f6.013f

AED

S1-OTV-2 VDC is shut down. It takes a few seconds to reconverge and S1-OTV-1 to become AED. During this time packets are dropped .

Failing pings to 4948-2

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 5

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

Host-210.0.0.102c84c.75f6.283f

Host-110.0.0.101c84c.75f6.013f

AED

S2-OTV-1# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- -----------10 c84c.75f6.013f 1 00:01:55 site Ethernet10/13

S1-OTV-1 takes over as AED but it does not have Host-2’s MAC in its CAM. Without the MAC in the CAM it cannot advertise the route to S2-OTV-1.

S1-OTV-1 will not advertise an OTV route until it sees a packet from Host-2 and the source MAC is added it to its CAM table. Host-2 is a ‘silent host’ and traffic sent to this device from S2-OTV-1 will be dropped.

AED Failing pings to 4948-2

S1-OTV-1# show mac add vlan 10Legend: * - primary entry, G - Gateway MAC, (R) - Routed MAC, O - Overlay MAC age - seconds since last seen,+ - primary entry using vPC Peer-Link VLAN MAC Address Type age Secure NTFY Ports/SWID.SSID.LID---------+-----------------+--------+---------+------+----+------------------O 10 c84c.75f6.013f dynamic 0 F F Overlay0

S1-OTV-1# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.013f 42 00:01:02 overlay S2-OTV-1

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 6

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

Host-210.0.0.102c84c.75f6.283f

Host-110.0.0.101c84c.75f6.013f

AED

S2-OTV-1# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.013f 1 00:03:47 site Ethernet10/13 10 c84c.75f6.283f 42 00:00:04 overlay S1-OTV-1

Generate traffic from Host-2, such as a broadcast or ping packet.

S1-OTV-1 learns Host-2 source MAC, programs it into its OTV route table and advertises it to S2-OTV-1. S2-OTV-1 OTV mac-routing table points to S1-OTV-1 and connectivity is restored.

AED Continuous pings to Host-2

S1-OTV-1# show mac add vlan 10Legend: * - primary entry, G - Gateway MAC, (R) - Routed MAC, O - Overlay MAC age - seconds since last seen,+ - primary entry using vPC Peer-Link VLAN MAC Address Type age Secure NTFY Ports/SWID.SSID.LID---------+-----------------+--------+---------+------+----+------------------O 10 c84c.75f6.013f dynamic 0 F F Overlay0* 10 c84c.75f6.283f dynamic 0 F F Po101

S1-OTV-1# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.013f 42 00:03:05 overlay S2-OTV-1 10 c84c.75f6.283f 1 00:00:05 site port-channel101

Send a ping to Host-1

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 7

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

Host-210.0.0.102c84c.75f6.283f

Host-110.0.0.101c84c.75f6.013f

AED

AED

Non-Silent Host (two hosts sending traffic)

S1-OTV-2# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.283f 1 00:06:44 site port-channel102 10 c84c.75f6.013f 42 00:06:14 overlay S2-OTV-1

S2-OTV-1# show otv route vlan 10

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.283f 42 00:06:25 overlay S1-OTV-2 10 c84c.75f6.013f 1 00:12:22 site Ethernet10/13

Continuous pings to Host-2

Continuous pings to Host-1

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 8

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

Host-210.0.0.102c84c.75f6.283f

Host-110.0.0.101c84c.75f6.013f

AED

AED

S1-OTV-2 VDC is shut down. It takes a few seconds to reconverge and for S1-OTV-1 to become the AED for Site 1. During this time packets are dropped .

Failing pings to Host-2

Failing pings to Host-1

© 2010 Cisco and/or its affiliates. All rights reserved. Cisco ConfidentialPresentation_ID 9

S2-OTV-1

S1-OTV-1

Extended Vlan 10

S1-OTV-2

Po101 Po102

Po64

G1/47

E10/13

E10/14

E2/17 E2/17

Host-210.0.0.102c84c.75f6.283f

Host-110.0.0.101c84c.75f6.013f

AED

Since host-2 is still trying to send packets to host-1. S1-OTV-1 learns host-2 MAC, updates its OTV route table and advertises the route to S2-OTV-1.

Only a brief outage is seen while S1-OTV-1 transitions to AED.

AED

S1-OTV-2# show otv route

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.013f 42 00:01:15 overlay S2-OTV-1 10 c84c.75f6.283f 1 00:00:32 site port-channel102

S2-OTV-1# show otv route

OTV Unicast MAC Routing Table For Overlay0

VLAN MAC-Address Metric Uptime Owner Next-hop(s)---- -------------- ------ -------- --------- ----------- 10 c84c.75f6.013f 1 00:17:50 site Ethernet10/13 10 c84c.75f6.283f 42 00:00:31 overlay S1-OTV-1

Continuous pings to Host-2

Continuous pings to Host-1