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<TITLE>weirdness with DHCP and 7960 phones..</TITLE>
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<DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN
class=709351721-10042006>I can see now why the phones do this (I guess as
protection from problematic DHCP servers), but it caught us off guard. We
figured that it should be up to the DHCP server to remember lease information,
not the device. For example, if a phone is unplugged from the network and
power removed, when it comes back up we expected a DHCP Discover to be broadcast
to initiate a new lease. At that point, if the DHCP server wanted to offer
it the same IP it had before, no problem. Instead the phone starts up with
a DHCP Renew (unicast).</SPAN></FONT></DIV>
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class=709351721-10042006></SPAN></FONT> </DIV>
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class=709351721-10042006></SPAN></FONT> </DIV><!-- Converted from text/plain format -->
<P><FONT size=2>---<BR>Bill Simon - bills@tns.its.psu.edu - (814) 865-2270<BR><A
href="http://tns.its.psu.edu/">http://tns.its.psu.edu/</A><BR><BR></FONT></P>
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<FONT face=Tahoma size=2><B>From:</B> Wes Sisk [mailto:wsisk@cisco.com]
<BR><B>Sent:</B> Monday, April 10, 2006 5:11 PM<BR><B>To:</B> Simon,
Bill<BR><B>Cc:</B> 'cisco-voip@puck.nether.net'<BR><B>Subject:</B> Re:
[cisco-voip] weirdness with DHCP and 7960 phones..<BR></FONT><BR></DIV>
<DIV></DIV>This was an interesting one - We found that MS dhcp server would
NOT send DHCP NAK for a renewal. So long as the phone does not receive a
NAK it will continue to use the same address. If the phone does not
receive any response it will continue to use the current address until the
lease expires.<BR><BR>Microsoft's behavior is to allow redundant DHCP servers
in the same subnet. If one server dies (controlling the lower half of
the range) the redundant server continues to function offering addresses from
the upper half of the range. But both dhcp servers must receive all DHCP
Discovers and Renews for this method to work and servers must not respond with
a NAK.<BR><BR>/Wes<BR><BR>Simon, Bill wrote:
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<DIV dir=ltr align=left><SPAN class=900395220-10042006><FONT face=Arial
color=#0000ff size=2>It's true, the 7960s do not obey the DHCP
protocol.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=900395220-10042006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=900395220-10042006><FONT face=Arial
color=#0000ff size=2>If they cannot talk to a DHCP server, they will use
whatever previous address they had.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=900395220-10042006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=900395220-10042006><FONT face=Arial
color=#0000ff size=2>We have complained to Cisco before about this disregard
for the protocol and were told it is "by design".</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=900395220-10042006></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=900395220-10042006><FONT face=Arial
color=#0000ff size=2>Our solution was to make gigantic DHCP pools for phones
so that there is plenty of address space available and it is unlikely that
we will have IP conflicts.</FONT></SPAN></DIV>
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<P><FONT size=2>---<BR>Bill Simon - <A class=moz-txt-link-abbreviated
href="mailto:bills@tns.its.psu.edu">bills@tns.its.psu.edu</A> - (814)
865-2270<BR><A
href="http://tns.its.psu.edu/">http://tns.its.psu.edu/</A><BR><BR></FONT></P>
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<FONT face=Tahoma size=2><B>From:</B> Tim Reimers [<A
class=moz-txt-link-freetext
href="mailto:tim.reimers@asheville.k12.nc.us">mailto:tim.reimers@asheville.k12.nc.us</A>]
<BR><B>Sent:</B> Monday, April 10, 2006 4:41 PM<BR><B>To:</B> <A
class=moz-txt-link-abbreviated
href="mailto:cisco-voip@puck.nether.net">cisco-voip@puck.nether.net</A><BR><B>Subject:</B>
[cisco-voip] weirdness with DHCP and 7960 phones..<BR></FONT><BR></DIV><!-- Converted from text/rtf format --><BR><BR>
<P><FONT face=Arial size=2>Hi everyone---</FONT> </P>
<P><FONT face=Arial size=2>We had a weird occurrence in the last few days
I thought I'd run past the group to see what everyone thought...</FONT>
</P><BR>
<P><FONT face=Arial size=2>A vendor (who shall remain nameless) rebuilt
our CCM -- and in the process, it turns out, failed to reinstall the DHCP
server/scope and TFTP options..</FONT></P>
<P><FONT face=Arial size=2>All worked fine until we had a power glitch of
some sort and the phones rebooted...</FONT> </P>
<P><FONT face=Arial size=2>At that point- well, that's when things get
weird..</FONT> </P>
<P><FONT face=Arial size=2>You'd think that NONE of the phones would come
back up ---</FONT> </P>
<P><FONT face=Arial size=2>but about 20 out of 75 did just that...
with no DHCP server.</FONT> </P>
<P><FONT face=Arial size=2>Mine, which was one that did it, is NOT set for
static addressing (none are)...</FONT> </P>
<P><FONT face=Arial size=2>Smoehow, it retained it's IP settings, though
it took a while to boot...</FONT> </P><BR>
<P><FONT face=Arial size=2>my question??? Wassup with that? I
thought "no dhcp, no boot', no NOTHING....for ALL of the phones on that
subnet?</FONT> </P>
<P><FONT face=Arial size=2>Why did some come up and work and others not?
Is there some magic in some of the boot code?</FONT> </P>
<P><FONT face=Arial size=2>(except perhaps a phone with a 169.254.x.x
address, trying to find a CCM, a load ID ,etc..)</FONT> </P>
<P><FONT face=Arial size=2>Tim</FONT> </P></BLOCKQUOTE><PRE wrap=""><HR width="90%" SIZE=4>
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