Recently I switched from a T1 to a residential cable service (Comcast). I have a virtual machine (XenServer 5.6) running Debian 6.0.6 that is acting as the default gateway for my home network, but for some reason it looks like the upstream DHCP server is ignoring my DHCPDISCOVER
requests completely.
Feb 1 20:58:34 myhost dhclient: Internet Systems Consortium DHCP Client 4.1.1-P1 Feb 1 20:58:34 myhost dhclient: Copyright 2004-2010 Internet Systems Consortium. Feb 1 20:58:34 myhost dhclient: All rights reserved. Feb 1 20:58:34 myhost dhclient: For info, please visit https://www.isc.org/software/dhcp/ Feb 1 20:58:34 myhost dhclient: Feb 1 20:58:34 myhost dhclient: Listening on LPF/eth1/26:ac:40:50:5b:c7 Feb 1 20:58:34 myhost dhclient: Sending on LPF/eth1/26:ac:40:50:5b:c7 Feb 1 20:58:34 myhost dhclient: Sending on Socket/fallback Feb 1 20:58:38 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 4 Feb 1 20:58:42 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 5 Feb 1 20:58:47 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 9 Feb 1 20:58:56 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 14 Feb 1 20:59:10 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 8 Feb 1 20:59:18 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 8 Feb 1 20:59:26 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 9 Feb 1 20:59:35 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 4 Feb 1 20:59:39 myhost dhclient: No DHCPOFFERS received. Feb 1 20:59:39 myhost dhclient: No working leases in persistent database - sleeping.
- Everything is cabled correctly, and the traffic is being bridged to the correct interface on the virtual machine. If I listen for all traffic using
tcpdump
, I can see lots of ARP traffic as well as my ISP's DHCP server responding to other customers who are requesting IP addresses. My DHCP packets are being broadcast but answers do not come back. - If I start
dhclient
before the modem has finished completely initializing, it serves a private IP address in the192.168.100.0/24
network range with a low refresh interval so thatdhclient
will pick up the public IP address when it is ready to be served. It continues to sendDHCPACK
responses for the private network until it is ready to bridge the networks, at which point I stop getting responses from a DHCP server again.
Feb 1 21:16:02 myhost dhclient: Listening on LPF/eth1/26:ac:40:50:5b:c7 Feb 1 21:16:02 myhost dhclient: Sending on LPF/eth1/26:ac:40:50:5b:c7 Feb 1 21:16:02 myhost dhclient: Sending on Socket/fallback Feb 1 21:16:04 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 8 Feb 1 21:16:04 myhost dhclient: DHCPOFFER from 192.168.100.1 Feb 1 21:16:04 myhost dhclient: DHCPREQUEST on eth1 to 255.255.255.255 port 67 Feb 1 21:16:05 myhost dhclient: DHCPACK from 192.168.100.1 Feb 1 21:16:05 myhost dhclient: bound to 192.168.100.10 -- renewal in 14 seconds. Feb 1 21:16:19 myhost dhclient: DHCPREQUEST on eth1 to 192.168.100.1 port 67 Feb 1 21:16:20 myhost dhclient: DHCPACK from 192.168.100.1 Feb 1 21:16:20 myhost dhclient: bound to 192.168.100.10 -- renewal in 13 seconds. Feb 1 21:16:33 myhost dhclient: DHCPREQUEST on eth1 to 192.168.100.1 port 67 Feb 1 21:16:36 myhost dhclient: DHCPREQUEST on eth1 to 192.168.100.1 port 67 Feb 1 21:16:43 myhost dhclient: DHCPREQUEST on eth1 to 192.168.100.1 port 67 Feb 1 21:16:50 myhost dhclient: DHCPREQUEST on eth1 to 255.255.255.255 port 67 Feb 1 21:16:51 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 7 Feb 1 21:16:58 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 15 Feb 1 21:17:13 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 7 Feb 1 21:17:20 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 10 Feb 1 21:17:30 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 10 Feb 1 21:17:40 myhost dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 12 Feb 1 21:17:52 myhost dhclient: No DHCPOFFERS received. Feb 1 21:17:52 myhost dhclient: No working leases in persistent database - sleeping.
- In my particular case, this is an EMTA modem that also provides phone service to my house. My phone service is working, I just can't get an IP address.
- I have tried calling in to my ISP and using the phone menu to send a reset signal to my modem, as well holding down the reset button to trigger a factory reset and re-download of firmware. Neither of these solved the problem.
- I have a spare DOCSIS 3.0 cable modem. I worked with a technician to temporarily whitelist its MAC address, but I'm having the exact same problem with not seeing DHCP responses.
I tried calling Comcast to ask them if my MAC address has been blacklisted somehow, but they are refusing to escalate my call without adding a premium technical support service to my account. (including a one-time activation fee to discourage me from immediately unsubscribing when my problem is solved)
Why can't my VM get a DHCP response?