Nexus 3K - Unable to ping between 2 of Nexus 3K via Vlan1

[thuy.hoang]

Dear Buddy,

I am facing with a weird issue on Nexus 3K (A & B)in my customer.

We have a pair of Nexus 3K are connected by 3 of 10G fiber as peer-link and a keep-alive link.

On each switches, we have Interface Vlan 1 and configured HRSP. The issue is 2 switches can not ping each others by Vlan 1, so HSRP on Interface Vlan 1 also not worked.

I tried to created others Vlan and all of them can work properly, excepted Vlan 1. Unfortunately, my customer want to use VLan 1 on their system.

My workaround is reboot 1 of 2 switches and Vlan 1 will work after reboot. But sometime, it will happen again.

I tried to did some troubleshooting and check below:

 - VLan 1 has been created and interface vlan 1 was up on both switches.

 - Checked peer-link and keep-alive link, both are good.

 - Can see each others in "show cdp neighbor details"

 - Can see Mac address and Ip address of each others in "show ip arp"

 - All vlan is allowed on trunk port and vPC links, included vlan 1.

 - Configured another native vlan on peer-link but still not work.

 - shut/ no shut interface vlan 1, not work.

Could anyone please to help me find out the root cause of this issue? or anyone had a experience on this.

I also attached the configuration of 2 switches and the logging that I got after issue appeared.

Thank you so much.

[balaji.bandi]

Not sure high level i looked you have some MAC address duplicate occuring.

2020 May 2 09:53:24 CoreSwitch_1 %ARP-3-DUP_VADDR_SRC_IP: arp [26796] Source address of packet received from 001d.aa8f.2754 on Vlan1(port-channel1) is duplicate of local virtual ip, 172.21.0.1
2020 May 2 09:53:34 CoreSwitch_1 %ARP-3-DUP_VADDR_SRC_IP: arp [26796] Source address of packet received from 001d.aa8f.2754 on Vlan1(Ethernet1/30) is duplicate of local virtual ip, 172.21.0.1

Switch 1 i can see some server switch - other side Switch 2 dont have config. - (i know it configured as Trunk) - check is there any device configured with .1 IP address.

[thuy.hoang]

Hi bro @balaji.bandi ,

Thanks so much for your sugesstion. I have resolved the MAC address duplicate, but i guess that it is not root cause of this case, i will keep monitoring.

Btw, I see some logging related to VLAN SUSPENDED. Could you please let me know the reason and it impact to system or not ?

Thank you.

2020 May 2 01:41:36 CoreSwitch_1 %ETHPORT-3-IF_ERROR_VLANS_SUSPENDED: VLANs 1,99-101,2000-2001 on Interface port-channel1 are being suspended. (Reason: vPC peer is not reachable over cfs)

2020 May 2 01:41:38 CoreSwitch_1 %ETHPORT-3-IF_ERROR_VLANS_REMOVED: VLANs 1,99-101,2000-2001 on Interface port-channel1 are removed from suspended state.

[balaji.bandi]

Some time you also get HSRP error, when the version is different on both the side.

fot your other issue ongoing please post below out put to understand :

From both the switch seperate file :

show ver 

show vpc brief

show vpc in-consistency check

show ip int br

ping each other using VRF soruce as  mgmt-interface and keep-alive,

show spanning-tree

show  fcs peers

sh system internal vpcm event-history errors

Other suggestion use system-priority command in vpc domain

[thuy.hoang]

Hi @balaji.bandi ,

HRSP shold be same on both.

I would to post the output as attached. 

Appreciated if you can help to find out something.

Currently, the system is running normally, but im very scare it will happen bad thing in future.

Thanks so much.