[cisco-voip] 'Bad ARP Add' on 7900 series logs

[Brian Meade (brmeade)]

Adam,

The ARP cache on the phone shouldn't be storing any entries from the data VLAN I believe.

I'm not aware what the limit is but I would say that I don't think the limit would be hit from legitimate traffic.  My guess would be this is due to some sort of broadcast storm or a bug.

The failure would most likely result in one-way/no-way audio for the call.

If you log into the SSH shell on the phone, you can run "sh arp" to take a look at the ARP cache and see how large it is.  I'd suggest taking some packet captures of the Voice VLAN to see what kinds of broadcast traffic you're seeing.

Brian

-----Original Message-----
From: Pawlowski, Adam [mailto:ajp26 at buffalo.edu] 
Sent: Friday, October 25, 2013 11:58 AM
To: Brian Meade (brmeade); Pawlowski, Adam; cisco-voip at puck.nether.net
Subject: RE: 'Bad ARP Add' on 7900 series logs

Brian,

I appreciate your insight

This is regarding the phone's software for voice functionality, and not applicable to traffic on the "PC" VLAN, right? 

Is there a sizing recommendation to the number of devices that are present on a subnet where it's phone-exclusive? The voice subnets are rather large. Perhaps, and I have to check on its current state, but disabling GARP would be helpful here? 

With a failure of adding an entry to the ARP cache, there could be a failure in operations with the phone with a call over some duration then? Are there other symptoms we could attribute to this?

Adam P
SUNYAB


> -----Original Message-----
> From: Brian Meade (brmeade) [mailto:brmeade at cisco.com]
> Sent: Friday, October 25, 2013 11:08 AM
> To: Pawlowski, Adam; cisco-voip at puck.nether.net
> Subject: RE: 'Bad ARP Add' on 7900 series logs
> 
> Adam,
> 
> When the phone creates a new socket for RTP TX/RX, it adds a permanent 
> entry to the ARP cache to protect from the ARP entry timing out during 
> the call.
> 
> After the call ends, this entry is supposed to be removed from the ARP 
> cache.
> 
> That same "bad ARP Add" is printed if the port fails to be added to 
> the permanent ARP cache or fails to be removed.
> 
> In your case, this is right after opening a new ingress channel via 
> OpenReceiveChannel at the beginning of the call.
> 
> I would guess something is most likely filling up your ARP cache on 
> the phones or something similar causing this to fail.  You should 
> probably see if there's a any sorts of broadcast storms on your 
> network that may be causing this issue.
> 
> Thanks,
> Brian
> 
> -----Original Message-----
> From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf 
> Of Pawlowski, Adam
> Sent: Friday, October 25, 2013 10:23 AM
> To: cisco-voip at puck.nether.net
> Subject: [cisco-voip] 'Bad ARP Add' on 7900 series logs
> 
> Every so often I find myself trolling through the logs on our phones 
> to ID or look for problems (which are rarely determinable here). I've 
> done pretty well figuring out most of what I'm looking at to be able 
> to deal with some of the basic stuff we'd run into , but, one message 
> keeps catching my eye and I'm not sure what it is .
> 
> When looking at a call in the log, often, but not always, I'll see:
> 
> 2320: NOT 14:29:39.746772 DSP: STREAM- OpenIngressChan- ChanType 1, 
> Remote (host 80xxxx85, port 585c), medType 4, Period 20, VAD 0, TOS 
> b8, stream (113182798, 113182798) --> chan 0
> 2321: NOT 14:29:39.747517 DSP: STREAM- OpenIngressChan- mix (1, 3), 
> dtmfpayloadtype 0
> 2322: WRN 14:29:39.748393 DSP: bad ARP Add, -126
> 2323: NOT 14:29:39.748959 DSP: Subtracted for CODEC[0] G.711 
> direction:1
> cost:13 old budget:87
> 
> Having, in the past, dealt with claims of dead air and no audio 
> between sets (though not readily reproducible), I've seen this but 
> can't figure out what it is supposed to be indicating, or if it's 
> pointing to something that could be a problem in our configuration.
> 
> Anyone know what it's warning about?
> 
> Adam P
> SUNYAB
> 
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