Strange ping pattern from Switch

[Antropitecus]

I have this issue where pinging an Avaya phone from a cisco Switch I get this pattern: !!.!!.!!.!!.!!.!!.!! so for each 2 packet going thrur I get 1 lost. As per field tech the avayas no look ok (dont know what kind of message he sees)

Please help.

[Georg Pauwen]

Hello,

as far as I remember, this is default behavior and a security measure against DoS attacks. I'll try and find some official document confirming this...

[Antropitecus]

But the phone is directly connected and it's an Avaya phone,...

[Georg Pauwen]

Hello,

do you have the same problem when pinging from a PC instead of the switch ?

[Antropitecus]

I'll try that and report back, I just saw switch is 2years uptime, could that be an issue?

[Georg Pauwen]

Yes, long uptimes can have a negative effect, however, the ping pattern is pretty consistent...

Which firmware version are you running on the Avaya ?

[Antropitecus]

Firmware version is 6.3116, I tried pinging from a server and it was ok. 

Regards. 

[Georg Pauwen]

Hello,

I did some more research, and it appears that Avaya IP Telephones implement an ICMP rate limiter.

If you send a ping from a (Microsoft) server, the pings are sent each second and do not trigger the rate limit. Cisco IOS devices however send pings at a much higher frequency (1/ms) and hence trigger the rate limit.

Try to use the extended ping from the Cisco and set the timeout to 1 or 2 seconds, you should not see the problem then.

[Antropitecus]

I tried 3 seconds timeout (default is 2) but still lose a packet, anyway explanation is coherent with what we've seen. 

Thanks.

[mlund]

Hi

When using cisco to send ping, it sends first ping, and as soon as the answer to first ping arrives, it sends the next ping and so on. So how long time there is between each ping depends on the round trip delay.

The timeout is only used to tell the cisco how long it should wait for the answer before sending the next ping. This is useful if the round trip delay is longer than 2 seconds, otherwise if ping returns out of this time cisco consider the ping as lost.

As far as I know, there isn't a way to increase the delay between the ping.

/Mikael

[Georg Pauwen]

Hello,

as per the thread below, CUCM is rate limiting ICMP packets coming from IOS devices (such as your switch). From a e.g. Windows PC you should not see this behavior.

https://supportforums.cisco.com/discussion/11177711/dropping-6th-icmp-packets