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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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cite="mid07A14D6987A5F647B2415D72EDF63B56043C441B@tnsex01.tns.its.psu.edu"
type="cite">
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<title>weirdness with DHCP and 7960 phones..</title>
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<div dir="ltr" align="left"><span class="900395220-10042006"><font
color="#0000ff" face="Arial" 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
color="#0000ff" face="Arial" 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
color="#0000ff" face="Arial" 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
color="#0000ff" face="Arial" 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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<br>
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<div class="OutlookMessageHeader" dir="ltr" align="left"
lang="en-us">
<hr tabindex="-1"> <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>
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<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>
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