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DHCP issue with EVPN+VxLAN+ARP suppression

satish.txt1
Beginner
Beginner

Folks,

 

I need your help here to understand what is going on. I have very simple spine-leaf design with OSPF+iBGP and my VTEPs in Cisco vPC pair for redendency. Everything was working until i enabled `suppress-arp`  (I did carve TCAM size also) on my L2VNI (I don't have L3VNI and anycast gateway). I found when my host server request for DHCP packet and it generate ff:ff:ff:ff:ff:ff packet and some kind of race condition hit start arp broadcast flooding in network and only solution is to turn off arp-suppression. I did this test multiple time to reproduce and it flood each time DHCP discovery/request happened. 

 

I believe this is some kind of vPC + Arp-suppression combo creating L2 arp loop. (can someone confirm or prove that arp-suppression isn't good idea with L2VNI only?)

 

I am running Cisco nexus 9396PX with nxos.9.3.5

1 ACCEPTED SOLUTION

Accepted Solutions

satish.txt1
Beginner
Beginner

After various test found L2VNI doesn't fully support apr-suppression, It does work but not in all condition. for experiment as soon as i create L3VNI for my VLAN and that fixed my issue so bottom line is if you have only L2VNI don't use arp-suppression (Without anycast Gateway). Period. 

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1 REPLY 1

satish.txt1
Beginner
Beginner

After various test found L2VNI doesn't fully support apr-suppression, It does work but not in all condition. for experiment as soon as i create L3VNI for my VLAN and that fixed my issue so bottom line is if you have only L2VNI don't use arp-suppression (Without anycast Gateway). Period. 

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