Ping your own IP secondary address

[e.ciollaro]

Hi,

I've got a router and when I ping my own IP address (on a point-to-point subinterface) the ping fails because on the other side of the link I've got a device not responding to ICMP echo request (this is correct as I read on in this forum).

The problem is: why can I successfully ping the IP secondary address on the same sub-interface ?

Thanks,

Enrico

[Kevin Dorrell]

The first part is not quite right. When you ping your own address on a point-to-point link, it is not up to the device on the other side of the link to respond to the ICMP. Instead, it is up to the device on the other side of the link to route the ICMP back to you, where you respond out and back again. The distinction is subtle, but gives us a clue as to what is going on in the second part of your question.

You can ping your secondary address. My guess is that the device on the other side of the link either does not have a route back to your primary address, or it has an access list preventing the ping. But it does have a route back to you secondary address. Is it that the other side of the link is configured on the secondary address subnet, but not on the primary?

Kevin Dorrell

Luxembourg

[e.ciollaro]

This is not the case because I've tried to reverse primary and secondary address and in this way I can ping the original IP address.

Is it possible that Cisco router behave differently between primary and secondary IP address ?