L2 traffic not passing through vPC Peer Link

[Plinio Brandao]

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

[InayathUlla Sharieff]

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

[Plinio Brandao]

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.