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Cisco Bug: CSCun25697 - (corner case) Ping/data may not work between n6k switches with L3 vlan

Last Modified

Feb 01, 2017

Products (1)

  • Cisco Nexus 7000 Series Switches

Known Affected Releases

7.1(0.1)

Description (partial)

Symptom:
Ping not working between leaf and host

Conditions:
This is a corner case where host has the arp entry of the proxy-gw & the we are trying to reconfigure the proxy-gw(leaf node-host VRF). There is no entry of the host in the Leaf Node during this configuration. Hence the continuous ping/data will be dropped between host and leaf node on VRF during the reconfiguring and after 10-15 mins of the reconfiguration of the Proxy-GW the ping will go through. Ping will go through when the arp refresh happens. The default arp refresh time is 25 minutes. So drops will be seen till arp refresh happens or the host sends a GARP.

If arp is empty on the leaf, this is expected behavior. In proxy mode, we don't trigger arp from the leaf. It is expected that the leaf always learns from GARP of the host(host speaks first). Since the arp on the leaf is empty, when the ping packet comes, there is no reply. In vinci, in the proxy mode, it is expected that the host will speak first. That is the reason why Host/VM sends GARP/RARP etc whenever it comes up. It makes sure that the leafs will have the mac address of the hosts. And, leafs will not generate any ARP packets towards the host side in proxy-mode.
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