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Nexus 7K ARP Cache marks certain IP addresses INCOMPLETE

I have been asked to investigate a connectivity issue, between a pair of nexus 7K switches in one DC and a Cat 65K across a VPLS in another DC. A simple diagram shows the connectivity:

ARP Cache issue.jpg

From the Cat 65k it is possible to ping and telnet to N7K1, but not N7K2.

The forwarding paths on all switches are correct. When a ping is attempted to N7K2 from the Cat the ARP cache on N7K2 briefly shows the Cat IP address in vlan 2001, as incomplete, then it ages out. The ARP cache on the Cat 65K and N7K1 both show the MAC and IP in vlan 2001 for N7K2.

If the STP block for vlan 2001 is moved to N7K1, the problem moves to that switch. Then it is possible to ping between the Cat and N7K2.

I see no reason for this, does anyone have suggestions for troubleshooting? I have no access to the third party supported VPLS, but can access all the switches.


Nexus 7K ARP Cache marks certain IP addresses INCOMPLETE

Oh well, turned out to be an ISP issue.