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1841 on a roadrunner modem

joebagodoe
Level 1
Level 1

I am setting up a 1841 router that the client already has with a low cost roadrunner cable connection. the 1841 he has was from a previous vendor with a T1. The 1841 does not have the cable modem card in it. I have tried quite a few things and I will attempt to list them. Firstly, I ensured the cable modem doesn't hold MAC addresses - I have connected my laptop to it and a Linksys router, and both times I recieve a WAN IP and can browse the intarweb.

I connected the modem to FE0/1 of the 1841 router, ensured it's admin up (pretty lights), set it to DHCP, but when I issue the "show ip interface brief" FE0/0 has my internal IP address, but FE0/1 isn't getting an IP. I thought that would be the simple part. before I did any of this, I formated flash, and loaded a new IOS onto the 1841 (c1841-adventerprisek9-mz.124-13a.bin). What am I missing?

18 Replies 18

Richard Burts
Hall of Fame
Hall of Fame

Joe

Some additional detail would be helpful. Can you post the output of show run interface fast0/1 and the output of show interface fast0/1?

The 1841 certainly should be able to talk to the cable modem and to get an IP address. Are there possibly speed and/or duplex issues?

HTH

Rick

HTH

Rick

I connected the port to our local LAN so it could pick up DHCP from it, but no go. I get full link lights and changed cables in case it was bad. I attached the run-conf and the show-int

Joe

Thanks for posting the additional information. I have looked at it and I do not see anything obvious that would explain the difficulty. I do have a couple of suggestions of things to try.

- I would like to see what happens if you remove this line:

ip broadcast-address 0.0.0.0

- I wonder about the interface speed as 100 Mb. I see the interface is configured for speed auto, but I wonder if the roadrunner is really doing 100 Mb. When you connect your PC and things work, could you check the Ethernet interface and verify what its speed is?

- I am not sure why you specify full duplex on the fast0/1 interface and suggest that you put duplex to auto.

- I wonder what would happen if you change fast0/1 to ip address dhcp (but without specifying the client-id)

- I would also suggest that you remove this line from fast0/1:

ip verify unicast source reachable-via rx allow-default 100

Give these a try (probably best to do one at a time) and let us know what happens.

HTH

Rick

HTH

Rick

foxbatreco
Level 3
Level 3

Hii..

As i can understand frm the post, u were able to access internet with linksys and cable modem , but not with 1841 when attached to CM ..rt??

The possible problem could be due to arp bindings on the cable modem.Ask ur provider to clear the current arp bindings for the modem (i.e with the linksys router) ...which doesnt allow data to be passed .

Pls do let us know of the outcome and rate the post if it helps.

Thank you for your suggestions. I will see if they work.

I have also connected the outside interface to our local network so I could see if it would receive DHCP from our server. It would not. I will post again after I look at those settings.

I tried the suggestions and nothing is helping. I have even flashed the ios to 12.4.13b, but it is not the problem. I have erased nv and started over with a fresh config, I have even followed the cisco guide (http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt1/1cfdhcp.htm)... it just won't pick up an IP. I am at a loss. I have absolutely no idea what is wrong. do I need a loopback or something? ARRG!

Attached is my run and int fa0/0 configs

Thanks for helping with this, I really need it!

Hi,

as suggested before, can you remove ip broadcast address 0.0.0.0 and all dhcp optoinal settings, do "term mon", then "debug ip dhcp" ?

I removed the broadcast from 0/1, but I cannot for some reason remove it from 0/0. Is there a better way of doing it than "no ip broadcast-address 0.0.0.0"?

Here is the result from the debug:

Router#debug dhcp

DHCP client activity debugging is on

Router#

*May 29 00:34:36.871: DHCP: deleting entry 637D7C58 0.0.0.0 from list

*May 29 00:35:06.503: DHCP: Try 133 to acquire address for FastEthernet0/0

*May 29 00:35:06.515: DHCP: allocate request

*May 29 00:35:06.515: DHCP: new entry. add to queue, interface FastEthernet0/0

*May 29 00:35:06.515: DHCP: SDiscover attempt # 1 for entry:

*May 29 00:35:06.515: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 00:35:06.515: DHCP: SDiscover 295 bytes

*May 29 00:35:06.515: B'cast on FastEthernet0/0 interface from 0.0.0

.0

*May 29 00:35:09.871: DHCP: SDiscover attempt # 2 for entry:

*May 29 00:35:09.871: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 00:35:09.871: DHCP: SDiscover 295 bytes

*May 29 00:35:09.871: B'cast on FastEthernet0/0 interface from 0.0.0

.0

*May 29 00:35:13.871: DHCP: SDiscover attempt # 3 for entry:

*May 29 00:35:13.871: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 00:35:13.871: DHCP: SDiscover 295 bytes

*May 29 00:35:13.871: B'cast on FastEthernet0/0 interface from 0.0.0

.0%Unknown DHCP problem.. No allocation possible

*May 29 00:35:26.995: DHCP: Waiting for 60 seconds on interface FastEthernet0/0

Hi,

please try:

ip broadcast-addresss 255.255.255.255

Alos please do clear counters and check that input packets is going up, as in the debug above seem like there is no answer to DCHP discovery.

I put that in, checked running-config, and the broadcast address line was gone. It then came back when it checked for DHCP server availability again.

It looks like the attempt count is increasing, but for some reason it still can't see my win2k3 DHCP server.

----LOG----

Router#clear counters

Clear "show interface" counters on all interfaces [confirm]

Router#

*May 29 01:47:56.854: %CLEAR-5-COUNTERS: Clear counter on all interfaces by cons

olede

Router#debug dhcp

DHCP client activity debugging is on

Router#

*May 29 01:48:23.886: DHCP: deleting entry 63B9823C 0.0.0.0 from list

*May 29 01:48:53.574: DHCP: Try 188 to acquire address for FastEthernet0/0

*May 29 01:48:53.586: DHCP: allocate request

*May 29 01:48:53.586: DHCP: new entry. add to queue, interface FastEthernet0/0

*May 29 01:48:53.586: DHCP: SDiscover attempt # 1 for entry:

*May 29 01:48:53.586: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 01:48:53.586: DHCP: SDiscover 295 bytes

*May 29 01:48:53.586: B'cast on FastEthernet0/0 interface from 0.0.0.0

*May 29 01:48:56.886: DHCP: SDiscover attempt # 2 for entry:

*May 29 01:48:56.886: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 01:48:56.886: DHCP: SDiscover 295 bytes

*May 29 01:48:56.886: B'cast on FastEthernet0/0 interface from 0.0.0.0

*May 29 01:49:00.886: DHCP: SDiscover attempt # 3 for entry:

*May 29 01:49:00.886: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 01:49:00.886: DHCP: SDiscover 295 bytes

*May 29 01:49:00.886: B'cast on FastEthernet0/0 interface from 0.0.0.0%Unknown DHCP problem.. No allocation possible

*May 29 01:49:14.066: DHCP: Waiting for 60 seconds on interface FastEthernet0/0

*May 29 01:49:44.886: DHCP: deleting entry 63B9823C 0.0.0.0 from list

*May 29 01:50:14.066: DHCP: Try 189 to acquire address for FastEthernet0/0

*May 29 01:50:14.078: DHCP: allocate request

*May 29 01:50:14.078: DHCP: new entry. add to queue, interface FastEthernet0/0

*May 29 01:50:14.078: DHCP: SDiscover attempt # 1 for entry:

*May 29 01:50:14.078: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 01:50:14.078: DHCP: SDiscover 295 bytes

*May 29 01:50:14.078: B'cast on FastEthernet0/0 interface from 0.0.0.0

*May 29 01:50:17.886: DHCP: SDiscover attempt # 2 for entry:

*May 29 01:50:17.886: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 01:50:17.886: DHCP: SDiscover 295 bytes

*May 29 01:50:17.886: B'cast on FastEthernet0/0 interface from 0.0.0.0

*May 29 01:50:21.886: DHCP: SDiscover attempt # 3 for entry:

*May 29 01:50:21.886: DHCP: SDiscover: sending 295 byte length DHCP packet

*May 29 01:50:21.886: DHCP: SDiscover 295 bytes

*May 29 01:50:21.886: B'cast on FastEthernet0/0 interface from 0.0.0.0%Unknown DHCP problem.. No allocation possible

*May 29 01:50:34.558: DHCP: Waiting for 60 seconds on interface FastEthernet0/0

It doesn't seem like anything is failing on the interface. I attached two "show controller"

Hello,

In my experience, when the router gets no reply to dhcp discover, is because the server is not offering an address. You may want to check with ethereal that the server is actually sending a reply to the router.

I set fa0/0 static to 192.168.0.3, and then set fa0/1 static to 192.168.0.4, and attempted to no shut fa0/1 and got this error:

% 192.168.0.0 overlaps with FastEthernet0/0

FastEthernet0/1: incorrect IP address assignment

I shut fa0/0 and no shut fa0/1 and could ping 192.168.0.4. I shut fa0/1 and no shut fa0/0 and could ping 192.168.0.3. So obviously there is a problem with a vlan or something? I'm running srvr 2k3 at home for DNS, domain, DHCP, and it is up and fine. It's address is 192.168.0.2. I'm on it right now and just released/renewd my IP.

Hello,

router ports in the router must fall in different subnets, so the overlap warning you are receiving is correct. So if you want 192.168.0/24 on the "inside", on the "outside" there should be some other address.

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