Inter VLAN communications drops

[mfields01]

I currently have 2 Nexus 9396 switches (Layer 3 core) and several Catalyst 3850 access layer 2 switches.

I have several users (not all) where inter vlan communication will drop. It happens for about a minute then corrects itself. This may happen a handful of times per day, but not everyday. Very inconsistent.

During my troubleshooting, I am able to access resources on my current VLAN but no other VLANs. I also can not ping the gateway.

Your help is appreciated.

[Ganesh Hariharan]

I currently have 2 Nexus 9396 switches (Layer 3 core) and several Catalyst 3850 access layer 2 switches.


I have several users (not all) where inter vlan communication will drop. It happens for about a minute then corrects itself. This may happen a handful of times per day, but not everyday. Very inconsistent.


During my troubleshooting, I am able to access resources on my current VLAN but no other VLANs. I also can not ping the gateway.


Your help is appreciated.

Hi,

If N9k is doing Core functionality and having all SVI configured , Could you check what show logging output showing in N9k and what is the show spanning tree vlan output for problematic vlan.

-GI

[mfields01]

There are no recent logs. The last one was from Oct 13th. We were having the issue yesterday. Below is the spanning tree info:

VLANxxx
  Spanning tree enabled protocol rstp
  Root ID    Priority    24677
             Address     xxxxxxxxxxxx
             This bridge is the root
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    24677  (priority 24576 sys-id-ext 101)
             Address     xxxxxxxxxxxxxx
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1              Desg FWD 1         128.4096 (vPC peer-link) Network P2p
Po2              Desg FWD 1         128.4097 (vPC) P2p
Po3              Desg FWD 1         128.4098 (vPC) P2p
Po4              Desg FWD 1         128.4099 (vPC) P2p
Po5              Desg FWD 1         128.4100 (vPC) P2p Peer(STP)
Po6              Desg FWD 1         128.4101 (vPC) P2p
Eth1/30          Desg FWD 2         128.286  P2p
Eth1/31          Desg FWD 2         128.287  P2p
Eth1/32          Desg FWD 2         128.288  P2p

[Ganesh Hariharan]

There are no recent logs. The last one was from Oct 13th. We were having the issue yesterday. Below is the spanning tree info:


VLANxxx
  Spanning tree enabled protocol rstp
  Root ID    Priority    24677
             Address     xxxxxxxxxxxx
             This bridge is the root
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    24677  (priority 24576 sys-id-ext 101)
             Address     xxxxxxxxxxxxxx
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1              Desg FWD 1         128.4096 (vPC peer-link) Network P2p
Po2              Desg FWD 1         128.4097 (vPC) P2p
Po3              Desg FWD 1         128.4098 (vPC) P2p
Po4              Desg FWD 1         128.4099 (vPC) P2p
Po5              Desg FWD 1         128.4100 (vPC) P2p Peer(STP)
Po6              Desg FWD 1         128.4101 (vPC) P2p
Eth1/30          Desg FWD 2         128.286  P2p
Eth1/31          Desg FWD 2         128.287  P2p
Eth1/32          Desg FWD 2         128.288  P2p

Hi,

With problem description what you have shared , i can sense either sep convergence is happening on the VLAN. Have you seen any link flaps in core 9K or in any of the access layer switches.

vPC between the N9k are showing correct output and you don't really see any logs on N9k.

-GI