[cisco-voip] ICMP to 7965 Phones - Packet loss when pinging from switch?

[Ryan Ratliff]

It's a DOS prevention mechanism.  The phones (and linux appliance servers) will drop pings that cone in over a certain threshold.  It just happens that Cisco routers and switches send pings at a rate much faster than Windows, and fast enough to trigger the phones to drop some.  

This is absolutely expected and has been this way for a long time.

-Ryan

On Feb 4, 2010, at 5:42 PM, Matthew Linsemier wrote:

All,

Today when I was troubleshooting some issues on our LAN I ran across a few very weird issues in regards to ICMP and both 7965 phones and our UCM servers.  In my scenario I have a 7965 phone connected to a 3750-PS switch using the voice VLAN.  When I ping the phone’s IP from either my Macbook (OSX) or Windows 7, the phone promptly responds with 0% packet loss and all is happy.  However, today I tried pining that same phone from our CCM voice gateway, and for whatever reason it was dropping every 6th packet or so.  I tried it from our core switch, same results.  Finally, I pinged it directly from the Cisco 3750 switch and again, had the same results, packet loss.  I can ping any Windows or OSX server across our network without any loss.  Should the phone be dropping any packets?  I remember reading once that the UCM servers had built in CSA software that may cause this type of result, but I wasn’t sure about the phones.  

We don’t seem to be having anyone complaining about voice calls, and the MOS scores all look good in the NAM.  I’m just a bit confused, and I would like everything on my network to be perfect!

Any input would be greatly apprecaited!

Matt
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