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Beginner

ARP Issues with Nexus Fabric

Hi,

I have been experiencing some arp issues across a nexus fabric. Basically we have 2 x data centres connected via a BGP/EVPN fabric using vxlan L2/3 routing and bridging. The problem originated when connectivity issues surfaced between some bare metal database servers dual homed on a port-channel/VPC to the nexus VPC domain in DC-1 and some host VM's in DC-2 ; communicating on the same vlan/vxlan segment. Basic icmp reachability would only work by disabling one of the server links connecting to Nexus-B effectively forcing the traffic across the peer-link. Originally we suspected server problems but it turns out the same issue is there for hosts/vms on UCS. To isolate the issue we tested/recreated the problem in DC-1 between a switch and a Cisco C-Series server. The Nexus does not seem to be forwarding the arp requests out the interface towards the server. This will work by enabling 'ip local proxy-arp' on the Anycast Gateway interface but this is not optimal solution. Anyone seen any behavior like this before.

Frank

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Accepted Solutions
Cisco Employee

Hi Frank,

Hi Frank,

did you resolve the issue ?

6 REPLIES 6
Cisco Employee

hi Frank,

hi Frank,

we faced similar issue were the N9K was dropping the ARP before it reaches CPU.

the issue was related to internal Bug and upgrade of NXOS FW resolved the issue

Beginner

Hi Yasser, Thanks for the

Hi Yasser, Thanks for the reply. I suspected as much.

Do you have bug id ?

Thanks

Cisco Employee

HI Frank,

HI Frank,

sorry for late reply :)

no i don;t have it but they recommend to upgrade to latest version available

Beginner

Thanks Yasser. Frank

Thanks Yasser.

Frank

Cisco Employee

Hi Frank,

Hi Frank,

did you resolve the issue ?

Beginner

Hi Yasser, I did but not by

Hi Yasser, I did but not by code upgrade. Bouncing port-channel interfaces rectified the issue so appears to be some kind of programming bug. Ethanalyzer previously showed the arps were hitting the CPU. The problem has not surfaced since so I plan to do a scheduled reboot soon and see how things go. Very strange/rare issue so must be some undocumented bug.

Frank

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