Ping requests from a Cisco device to an Avaya IPSI board

[r.ossanna]

Hello. I have an interesting problem when trying to ping an Avaya IPSI (IP Signalling Interface) board from any Cisco device. When I try and ping the device, from say, a 4506, It appears to time out on every other ping request. Example:

#ping 172.16.99.43

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.99.43, timeout is 2 seconds:

!.!.!

Success rate is 60 percent (3/5), round-trip min/avg/max = 1/1/1 ms

But from a Windows device, no such issues. Any other Avaya device responds correct, just the IPSIs.

Any ideas?

[pcameron]

Many VOIP devices use ICMP rate limiting to prevent denial of service attacks. You don't want the VOIP box from having to continually service interupts for pings or other low priority ICMP traffic when it is trying to process real time voice traffic.

It's quite possible that the interval between pings from the windows PC is much longer, so the target device is quite happy to service these ping requests, while the interval between the pings from the IOS device is much shorter so the target device drops every second reply.

You will actually see exactly the same behaviour when pinging a Cisco IP phone from a router and from a Windows PC - every second ping from the router is lost, while all pings from the PC are responded.

Since Cisco IP phones have been doing this for years, I suppose we should be flattered that Avaya appear to have thought it was such a good idea it was worth copying :-)

[r.ossanna]

Thanks for the reply and the chuckle!

Avaya seems to have an issue with the IPSI board doing warm reboots to the PBX it is attached to. I get's what it calls a sanity check, meaning the IPSI does not get a timely response to its "heartbeat" request. When I saw the behavior on the Cisco device, I thought that might be an issue.

Thanks again.