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Implementation details are going to be device specific. What model
phone are you using? Do you have a packet capture? /Wes<br>
<br>
On Thursday, July 01, 2010 11:38:38 AM, Pawlowski, Adam
<a class="moz-txt-link-rfc2396E" href="mailto:ajp26@buffalo.edu"><ajp26@buffalo.edu></a> wrote:<br>
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<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Would you
have any idea as to
the behavior of the device when the cache is full ? It doesn’t appear
that Option 35 is set, so if that is correct then the timeout would be
40
minutes. Since you can call numerous endpoints in that timespan I would
assume
it drops the oldest non-permanent entry. However, even with this
behavior,
should it not still be able to successfully open the RTP stream, even
if
it were delayed in resolving the IP address ? Is there, then, perhaps
a
problem with Gratuitous ARP being enabled, in that it is overflowing
the table
and causing a problem ? I logged into the phone via SSH, but there
doesn’t
seem to be a way to view the table from the device to see what it is
populated
with.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Thank you
for your reply,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);">Adam<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
Wes Sisk [<a class="moz-txt-link-freetext" href="mailto:wsisk@cisco.com">mailto:wsisk@cisco.com</a>] <br>
<b>Sent:</b> Thursday, July 01, 2010 10:58 AM<br>
<b>To:</b> Pawlowski, Adam<br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a><br>
<b>Subject:</b> Re: [cisco-voip] 7900 series and ARP<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The phones also have a very limited arp cache, I
believe 16
entries. ARP entries corresponding to next hop for CM servers are
permanently cached. Recommendation is to avoid deploying phones in
such a
large L2 domain. I believe this is covered in the UC SRND. There is
some history behind this:<br>
<br>
CSCdt28640 7960 Intermittant Delayed Dialtone when going off-hook<br>
<br>
/Wes<br>
<br>
On Wednesday, June 30, 2010 11:11:18 AM, Pawlowski, Adam <a
moz-do-not-send="true" href="mailto:ajp26@buffalo.edu"><ajp26@buffalo.edu></a>
wrote:<br>
<br>
<o:p></o:p></p>
<p class="MsoNormal">Folks,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"> I’ve seen some commentary about
certain versions of Call Manager not being suitable to sit directly on
a
subnet with a large number of endpoints due to a limited capacity of
the ARP
table, but, nothing similar from the VoIP telephones themselves.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"> I have a large subnet of VoIP
devices, a /19 with over 1500 phones active at this time. Within this
subnet,
and, specifically, within a “building”, subset of network gear,
there are specific telephones which are not able to complete a call to
another
telephone on that subnet, within the “building”. Each of these
devices is direct attached to a Cat 3750G placing the voice traffic on
the sub
mentioned before. <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"> What I’ve seen in the one
time I was able to isolate the problem, was the one of the two phones
in the
conversation would be continually ARPing for the other device, but, the
other
device, despite seeing it, wouldn’t reply, so the RTP stream never
establishes. I toggled the GARP feature from off, to on (although we
have
phones elsewhere with it off and/or on) and it began working. The
problem still
exists with other, specific, sets, but, the feature is on and swapping
it
doesn’t help. Often, a second try at establishing a call will work. <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"> I guess what I’m asking
is, is there a limit to the ARP table on the device? Does it even
matter, since
it attempts to lookup the MAC of the target phone on each call ? Anyone
else
had to deal with this ? <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"> You’ll see an error in
the device’s console log about 0 RTP packets received, and stream stats
will
show no traffic sent or received, but, of course, the phone presents as
though
the call is flowing and thus the end users complain.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Thanks for your insights,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Adam Pawlowski<o:p></o:p></p>
<p class="MsoNormal">University at Buffalo<o:p></o:p></p>
<pre><o:p> </o:p></pre>
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<pre><o:p> </o:p></pre>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>cisco-voip mailing list<o:p></o:p></pre>
<pre><a moz-do-not-send="true"
href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</a><o:p></o:p></pre>
<pre><a moz-do-not-send="true"
href="https://puck.nether.net/mailman/listinfo/cisco-voip">https://puck.nether.net/mailman/listinfo/cisco-voip</a><o:p></o:p></pre>
<pre> <o:p></o:p></pre>
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