IP Address DHCP to Cox cable modem Question

[westmanm]

I've got a Cox cable connection that I'm trying to hook a spare 2621 up to. I've got it so it works wonderfully if I put in the address that was DHCPed to my laptop, but the router won't go and get it's own.
I'm running 12.2 so it should be able to do this. But, when I try the show ip interface brief command just says unassigned for the address. When I hardcode an address back in it works beautifuly, but there's no way to tell how long that address will last.
Does anyone know what I need to do to get this to work?

Thanks
Mike

 

[westmanm]

Update:
I did a debug all and one of the things that I saw was this:

00:26:55: DHCP: Received a BOOTREP pkt Ack for our Inform
00:26:55: DHCP: Scan: Message type: DHCP Offer
00:26:55: DHCP: Scan: Server ID Option: 172.19.81.19 = AC135113
00:26:55: DHCP: Scan: Lease Time: 86400
00:26:55: DHCP: Scan: Renewal time: 43200
00:26:55: DHCP: Scan: Rebind time: 75600
00:26:55: DHCP: Scan: Subnet Address Option: 255.255.254.0
00:26:55: DHCP: Scan: Time Offset: 4294949296
00:26:55: DHCP: Scan: Router Option: 68.229.178.1
00:26:55: DHCP: Scan: Time Server Option: 172.19.81.19
00:26:55: DHCP: Scan: DNS Name Server Option: 68.13.16.25, 68.13.16.30, &68.12.1
6.30&
00:26:55: DHCP: Scan: Log Server Option: 172.19.81.19
00:26:55: DHCP: Scan: Domain Name: om.cox.net
00:26:55: DHCP: rcvd pkt source: 68.229.178.1,  destination:  255.255.255.255
00:26:55:    UDP  sport: 43,  dport: 44,  length: 332
00:26:55:    DHCP op: 2, htype: 1, hlen: 6, hops: 1
00:26:55:    DHCP server identifier: 172.19.81.19
00:26:55:         xid: 0, secs: A00, flags: 8000
00:26:55:         client: 68.13.182.173, your: 68.229.178.91
00:26:55:         srvr:   172.19.81.19, gw: 68.229.178.1
00:26:55:         options block length: 84
 
00:26:55: DHCP Offer Message   Offered Address: 68.229.178.91
00:26:55: DHCP: Lease Seconds: 86400    Renewal secs:  43200    Rebind secs:   7
5600
00:26:55: DHCP: Server ID Option: 172.19.81.19 No-IPL. Punted

Any idea in there what it didn't like?

Thanks

 

[westmanm]

Anyone?

 

[Ciscon]

I dont remeber the exact command but I think it was something like ip rarp or something like that. I'll look tonight on ym router when I get home.

 

[netadmin65]

I have used a Cisco 2611 for several years (up until last
week) without any problems. I am also on Cox Cable. I did
not change any of the router config, yet for some reason
it stopped working for me a week or so ago.

If someone else can help with this problem, please reply.
Otherwise, I'll give you the basics of what worked for me.

First of all, the IOS needs to be 12.1(3) or later, and
a "T" build for 'ip address dhcp' to work. They may have
kept this in later non "T" builds, I am not sure.

Instead of 'debug all' as mentioned, I recommend just
'debug dhcp detail'. You'll be wading through alot less
junk.

Anyhow, all you'll need to grab an address via DHCP from
Cox's DHCP server is the 'ip address dhcp' command. Once
again, this worked for me until recently. If this is the
only problem, then I encourage someone from Cox to tell us
what the heck is going on!

If you are then using the router to perform NAT, you'll
need the interface thats getting its address from the ISP
to also have 'ip nat outside', and the LAN interface to
have 'ip nat inside'. You'll also need to set up a source
list using an ACL. Google on 'ip nat inside source' and
you should get a few good configs that show how this is
done. Finally, if your router is getting its address via
DHCP, yet you want the router to supply a DHCP pool of
internal addies to the NATed LAN, then you also need to
set up a dhcp pool, using 'ip dhcp pool', etc.

If you need more explanation, please let me know.
Otherwise, anyone out there reading this that can
help with my Cox and Cisco problem, please don't hesitate
to reply. My router will get an address, but it is
a Cox internal address of 10.255.x.x instead of the
normal 68.102.x.x address. The PCs that connect directly
are fine.

 

[netadmin65]

Also, Cox has started recognizing option 60 in DHCP as
of several weeks ago. This means that you need to upgrade
the IOS to 12.2(12)T or better according to Cisco, although
I've seen some 12.2(11)T builds work.

Any other questions about hooking up a Cisco router
to a non-Cisco cablemodem can be found at:

http://www.cisco.com/warp/public/109/router_behind_cm_19268.shtml

Hope this helps

 

[westmanm]

Thanks netadmin, I'd just found something allong those lines.

-Mike

 

[murk2]

I had the same exact problem with my 2514. I upgraded the IOS to 12.2(19) and it is working fine again.

 

[scuta68]

I have a 2514, just upgraded the IOS to 12.3.3 in hopes that I would be able to use the IP ADDRESS DHCP command, alas the command is not an available command. Any suggestions would be most welcome. I am not behind a Cox cable modem, but a Verizon DSL modem.



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