There is a problem with the ISC's DHCP client (including all LRP 
version) with the TTL being hardcoded to 16.  This started giving me 
(and others) problems last Monday when AT&T broadband "upgraded" 
their systems in the St. Paul/Minneapolis area.  

Turns out that now the DHCP server is (no joke) 18 hops away from me. 
 Since the DHCP client sets the DHCPDISCOVER packet TTL to 16, the 
message never gets to the server.  The "fix" is to hack the ISCP DHCP 
source code and use a larger value (i.e. 128) in the TTL field.  
AFAIK, the Microsoft DHCP client uses a value of 128 in the TTL 
field.

The message below was sent by Paul Dokas where he outlines how to do 
this.

Can someone make an updated dhclient package with this change 
incorporated?  FWIW, I'm running the Dachstein 1.0.2 distribution.  
My home network is useless without it. :-(

PS: I found a newsgroup message outlining the same problem and fix, 
so I know there are others out there who are having similar problems. 
 Here's the Google URL:

http://groups.google.com/groups?selm=c91381b2.0206210920.269f9e1b%40po
sting.google.com


------- Forwarded message follows -------

[snip]

Found the problem.  The ISC DHCP client sets the TTL on the DHCP
request to 16, which is apparently too low for AT&T's network.  This
would explain why it works for some people and not other on an
apparently random basis.


I edited line 159 of common/packet.c in the ISC DHCP source code.  It
used to be:

  ip.ip_ttl = 16;

and I changed it to be:

  ip.ip_ttl = 128;


And, now I get a lease almost immediately after running dhclient.


So, I guess that AT&T's DHCP servers are just fine (I don't need to
set any strange options in dhclient.conf).  The "problem" is that the
Internet, or at least AT&T's broadband network, has grown larger than
what the source code assumes to be a *big* network.


I'll send in a bug report to ISC first thing in the morning.


Paul
------- End of forwarded message -------




Ethan Galstad,
Nagios Developer
---
Email: [EMAIL PROTECTED]
Website: http://www.nagios.org



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