arp cache problem? (not4 possible pinging vlan interface ip)

[sir_hiss]

I'm wondering about the PING-Request behaviour of an OS6400-Stack.
The switches are monitored by nagios behind a NAT-Router and sometimes the switch don't answers ping requests.
I can see the ping request for the switch-IP on the corresponding switchport for this routerinterface. And I can see the routers arp request for the switch-IP but no answer from the switch. After some arp requests the switchs IP interface broadcasts itself a "who has" with it's own IP...

Is there any way for listing the switchs arp cache? -->show mac-address-table only shows the switch ports connected devices but not its own arp cache
Or do you have any ideas?

[benny]

Switch-> show arp

If the switch asks for itself - there might be a duplicate IP address.

More likely you have issues with STP and your topology is instable.

-benny

[sir_hiss]

no this is without STP an it seems to be a problem of the NAT-router and not the switch.
Thanks for your response!