What firmware are you running on these phones ? You are running a /24 subnet for your phones, which is pretty standard. I have never heard of this kinda of problem happening before due to ARP issues in a /24 subnet.<div>
<br></div><div>Are you having this problem at more than one location? Can you run a packet capture on that subnet ? I wonder if you have someone messing around on your network (e.g. man in the middle attack)<br><br><div class="gmail_quote">
On Mon, Oct 8, 2012 at 5:41 PM, Amanda Lalli-Cafini <span dir="ltr"><<a href="mailto:alalli@iinet.net.au" target="_blank">alalli@iinet.net.au</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div lang="EN-AU" link="blue" vlink="purple"><div><p class="MsoNormal"><span style>Hi Ryan,<u></u><u></u></span></p><p class="MsoNormal"><span style><u></u> <u></u></span></p><p class="MsoNormal"><span style>Thanks for that.<u></u><u></u></span></p>
<p class="MsoNormal"><span style>We do not have any 9971 phones in this setup.<u></u><u></u></span></p><p class="MsoNormal"><span style>Most are 7941 and 7942 models. There are a few 7961 phones and a few 9951 phones.<u></u><u></u></span></p>
<p class="MsoNormal"><span style><u></u> <u></u></span></p><p class="MsoNormal"><span style>The problem I am trying to solve is that some of the 7942 phones just appear to drop off of the network from time to time.<u></u><u></u></span></p>
<p class="MsoNormal"><span style>When this occurs, I can not ping the phone even from its own default gateway, yet it is still registered to CUCM and can make/receive calls.<u></u><u></u></span></p><p class="MsoNormal"><span style>I however, get one way audio from that phone when the problem occurs.<u></u><u></u></span></p>
<p class="MsoNormal"><span style><u></u> <u></u></span></p><p class="MsoNormal"><span style>We are thinking that their arp cache (something small like 16) is getting full and wanted to be able to flush that out every five minutes with the dhcp option.<u></u><u></u></span></p>
<p class="MsoNormal"><span style>Is there a way to set the ARP cache timeout from within Call Manager itself by any chance?<u></u><u></u></span></p><p class="MsoNormal"><span style><u></u> <u></u></span></p><p class="MsoNormal">
<span style>Thanks for any help.<u></u><u></u></span></p><p class="MsoNormal"><span style><u></u> <u></u></span></p><p class="MsoNormal"><span style>Regards<u></u><u></u></span></p><p class="MsoNormal"><span style><u></u> <u></u></span></p>
<p class="MsoNormal"><span style>Amanda<u></u><u></u></span></p><p class="MsoNormal"><span style><u></u> <u></u></span></p><div><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0cm 0cm"><p class="MsoNormal">
<b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Ryan Ratliff [mailto:<a href="mailto:rratliff@cisco.com" target="_blank">rratliff@cisco.com</a>] <br>
<b>Sent:</b> Monday, 8 October 2012 10:56 PM<br><b>To:</b> <a href="mailto:alalli@iinet.net.au" target="_blank">alalli@iinet.net.au</a><br><b>Cc:</b> <a href="mailto:cisco-voip@puck.nether.net" target="_blank">cisco-voip@puck.nether.net</a><br>
<b>Subject:</b> Re: [cisco-voip] setting the ARP cache timeout for phones using DHCP option<u></u><u></u></span></p></div></div><div><div class="h5"><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">CSCtf62463 seems to indicate the 9971 phones don't support DHCP option 35. This will vary by model so YMMV.<u></u><u></u></p>
<div><p class="MsoNormal"><u></u> <u></u></p><div><p class="MsoNormal"><span><span style="font-family:"Helvetica","sans-serif"">-Ryan</span></span> <u></u><u></u></p></div><p class="MsoNormal"><u></u> <u></u></p>
<div><div><p class="MsoNormal">On Oct 8, 2012, at 4:10 AM, <a href="mailto:alalli@iinet.net.au" target="_blank">alalli@iinet.net.au</a> wrote:<u></u><u></u></p></div><p class="MsoNormal"><u></u> <u></u></p><div><div><div>
<div><div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Currently Being Moderated<u></u><u></u></span></p></div><h2><span style="font-family:"Helvetica","sans-serif""><a>Configuring the ARP cache timeout for Cisco phones</a><u></u><u></u></span></h2>
</div></div><div><div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Hi All,<u></u><u></u></span></p><div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p>
</div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">I am hoping to configure the ARP cache timeout for Cisco phones using the dhcp option.<u></u><u></u></span></p><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">I was wondering if anyone here has done it or can verify that this would be correct.<u></u><u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Say for example I have a DHCP pool named VOICE.<u></u><u></u></span></p>
<p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">In this network, the CUCM is located at IP address 10.2.200.110 <u></u><u></u></span></p><div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p>
</div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">I did some google searching and found a Wiki site with the various dhcp options defined in it.<u></u><u></u></span></p><div><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""><a href="http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol" target="_blank">http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol</a><u></u><u></u></span></p>
<p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">According to the site, dhcp option 35 is used as the ARP Cache Timeout value and it is 4 bytes long.<u></u><u></u></span></p><div><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Lets say that I would like to set my arp cache timeout to be 300 seconds.<u></u><u></u></span></p>
<p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">I convert 300 to hex and get 12C.<u></u><u></u></span></p><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Since my field will need to be four bytes long this becomes 0000.012C.<u></u><u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">I think that the following dhcp pool will provide 300 seconds for the phone ARP cache timeout.<u></u><u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">ip dhcp pool VOICE<u></u><u></u></span></p>
<p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">network 10.240.1.0 255.255.255.0<u></u><u></u></span></p><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">default-router 10.240.1.1<u></u><u></u></span></p>
<p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">option 150 ip 10.2.200.110<u></u><u></u></span></p><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">option 35 hex 0000.0c12 <u></u><u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Can anyone help me out with a verification or point me in the direction of the appropiate documentation?<u></u><u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Many thanks for any assistance.<u></u><u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Regards<u></u><u></u></span></p>
<div><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif""> <u></u><u></u></span></p></div><p><span style="font-size:9.0pt;font-family:"Helvetica","sans-serif"">Amanda Lalli-Cafini<u></u><u></u></span></p>
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