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Webcast-Catalyst9k
New Member

L2 traffic not passing through vPC Peer Link

Hi Community,

I'm facing some problems and I'd like to share with you to check if my understand is correct or not.

I'm attaching the topology to help with the understanding.

In normal situation, traffic is able to pass from the 5K to the 6500. However, if the active uplink goes down I was also expecting traffic to pass over the link that connects the two 5Ks, but this is not happening.

In other words, if the traffic goes through from SRV-B- -> N5k2 -> 6k5-2 -> SRV-C everything works fine.

If the traffic goes through SRV-A -> N5k1 -> N5k2 -> 6k5-2 -> SRV-C or SRV-B -> N5k2 -> N5k1 -> SRV-A we face the problem. On both directions.

If I change the root priority for 6k1, traffic SRV-A- -> N5k1 -> 6k5-1 -> 6k5-2 -> SRV-C works fine.

My understanding is that the traffic that throughout the vPC Peer Link isn’t completing.

We are testing from a server on the Enclosure to a Server outside of Nexus ambient. On both directions the problem persists.

If I change the root priority to a vlan doing the traffic go “ahead” without pass by the vPC Peer link, works.

If I removed the vPC Peer link configuration and configure a simple trunk between both N5k, everything works.

According to this document, Orphan ports can communicate between vPC Peer Link.

http://www.cisco.com/en/US/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf

So, what can be happening?

Thank you in advance.

N5k1-config

N5k1# sh run

!Command: show running-config

!Time: Thu Aug 29 19:23:19 2013

version 5.1(3)N2(1)

feature telnet

no feature http-server

feature tacacs+

cfs eth distribute

feature udld

feature interface-vlan

feature hsrp

feature lacp

feature vpc

logging level vpc 6

feature lldp

feature fex

!

spanning-tree port type edge bpduguard default

!

vpc domain 50

  role priority 50

  peer-keepalive destination 10.251.32.12 source 10.251.32.11

  delay restore 360

  auto-recovery

  ip arp synchronize

interface port-channel5

  description ### PEER-LINK 5kA-to-5kB ###

  switchport mode trunk

  spanning-tree port type network

  speed 10000

  vpc peer-link

interface Ethernet1/17

  description ### Uplink_to_Enclosure-03 ###

  switchport mode trunk

  switchport trunk allowed vlan 4-7,9,17,40,80-81,115

interface Ethernet1/18

  description ### Uplink_to_Enclosure-03 ###

  switchport mode trunk

  switchport trunk allowed vlan 4-7,9,17,40,80-81,115

interface Ethernet1/28

  description ### Uplink_to_6K5-1 ###

  switchport mode trunk

  switchport trunk allowed vlan 4-7,9,17,40,80-81,115

interface Ethernet1/29

  switchport mode trunk

  channel-group 5 mode active

interface Ethernet1/30

  switchport mode trunk

  channel-group 5 mode active

N5k2-config

N5k2# sh run

!Command: show running-config

!Time: Thu Aug 29 19:23:19 2013

version 5.1(3)N2(1)

feature telnet

no feature http-server

feature tacacs+

cfs eth distribute

feature udld

feature interface-vlan

feature hsrp

feature lacp

feature vpc

logging level vpc 6

feature lldp

feature fex

!

spanning-tree port type edge bpduguard default

!

vpc domain 50

  role priority 100

  peer-keepalive destination 10.251.32.11 source 10.251.32.12

  delay restore 360

  auto-recovery

  ip arp synchronize

interface port-channel5

  description ### PEER-LINK 5kB-to-5kA ###

  switchport mode trunk

  spanning-tree port type network

  speed 10000

  vpc peer-link

interface Ethernet1/15

  description ### Uplink_to_Enclosure-02 ###

  switchport mode trunk

  switchport trunk allowed vlan 4-7,9,17,40,80-81,115

interface Ethernet1/16

  description ### Uplink_to_Enclosure-02 ###

  switchport mode trunk

  switchport trunk allowed vlan 4-7,9,17,40,80-81,115

interface Ethernet1/28

  description ### Uplink_to_6K5-2 ###

  switchport mode trunk

  switchport trunk allowed vlan 4-7,9,17,40,80-81,115

interface Ethernet1/29

  switchport mode trunk

  channel-group 5 mode active

interface Ethernet1/30

  switchport mode trunk

  channel-group 5 mode active

2 REPLIES
Cisco Employee

L2 traffic not passing through vPC Peer Link

Plinio,

I am not strong on N5K but looking at this I can say that you are seeing this as expected behaviour.

The reason is that the data which is recieved from Member port passing through the VPC peer link will not pass to other member port this is by design.

You can fully utilize the VPC feature connecting another link from servers A& B to N5k2/1 and forming the VPC among them which would help .

May be someother who are expert in N5K might help you here.

HTH]

Regards,

Inayath

New Member

L2 traffic not passing through vPC Peer Link

Hi Inayath,

Thank you for your feedback.

According to the Orphan Ports traffic.png that I attached from a Cisco document, 2 orphan devices can communicate using the vPC peer link. My both enclosure are "orphans" and they are trying to use this link to communicate.

I'm not able to connect the enclousure to the other Nexus in this moment, so my intention is understand how is this scenario's behavior or if it's impossible to use this design.

Thank you in advance.

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