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Old 05-25-2004, 12:16 PM   #1
pengcow
LQ Newbie
 
Registered: Dec 2002
Posts: 2

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dhcp w/ comcast not setting default route


After rebooting for the first time in a while, I had some problems getting my network working again. I have a Comcast cable modem, and when bringing up the network connection, dhclient was able to get an ip but it wasn't setting a default route. I've managed to solve this by setting the route manually every time I have to bring the interface back up, but I'd feel better if I found the source of the problem instead of just a workaround.

After bringing up the interface, the following routes were set:
Code:
[root@annulus dhcp]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
68.83.208.0     0.0.0.0         255.255.248.0   U     0      0        0 eth0
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
with my ip address being 68.83.213.56

Looking in /var/lib/dhcp/dhclient.leases:
Code:
lease {
  interface "eth0";
  fixed-address 69.140.76.118;
  filename "mdcm315_v1_silver_c01";
  option subnet-mask 255.255.248.0;
  option routers 69.140.72.1;
  option dhcp-lease-time 604800;
  option dhcp-message-type 5;
  option dhcp-server-identifier 172.30.100.36;
  option domain-name-servers 68.48.0.5,68.87.96.15,68.48.0.6,68.87.96.16;
  option domain-name "alxndr01.va.comcast.net";
  renew 4 2004/5/27 07:33:22;
  rebind 0 2004/5/30 07:14:03;
  expire 1 2004/5/31 04:14:03;
}
you can see that dhclient was getting router information. Unfortunately, this ip address was not reachable with the routing tables set up the way they were. By setting the default gateway manually to 68.83.208.1, everything works fine.

So either this is a bug/config problem with dhclient (searching the dev lists didn't turn anything up) or a config problem with Comcast's dhcp server which causes it to send out the wrong router.

Oh, and when I boot into win2k, the network comes up just fine - which means either the problem is with dhclient OR windows automagically works around the problem by trying alternative gw's until it finds one that works ???

Anybody else have this problem or have any insight?
 
  


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