Can Anyone Help Me With 1751 DSL Connection

Unanswered Question
Apr 29th, 2008


I have made 2 other posts about this issue and haven't gotten any good results back. Please someone help me, I don't think this is that complicated of an issue.

I've got a regular house-hold DSL service with the modem set into bridge mode, so it will pass a public IP across to the router. It works fine with my linksys router (ofcourse), but I cannot get a connection out of the cisco 1751. The IP address coming from my provider is done via DHCP.

I can't get the 1751 to send out a PPPoE login and get authenticated to get an IP. DSL modem is plugged into eth 0/0 and LAN into fasteth 0/0. This really should be basic stuff, I don't know why no one has been able to help me so far. I will provide config if requested, but want someone to come up with something other than what I have, obviously.


I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4 (2 ratings)
Paolo Bevilacqua Tue, 04/29/2008 - 09:21

Chances are the link doesn't sync up at all.

Please check "show dsl interface" and "show version". This is to know which ADSL FW you're running.

sandman420 Wed, 04/30/2008 - 06:21

I actually am doing this with a wic-1enet interface instead of the adsl card. My DSL modem from the provider has ethernet out, so normally (just like with my linksys router) I put the modem in bridge mode so as to let my router perform the PPPoE login and obtain an IP address from the provider.

Someone told me to do a debug on ppp negotiation and authentication and told me that what it showed is that there wasn't any negotiation or authentication. I never got a response back as to what to do about that or to try really, so I'm hoping that someone else can maybe help me if I make enough posts about it.

Paolo Bevilacqua Wed, 04/30/2008 - 10:18

Hi, when taking the debugs, also enable "term mon". You can also post you config, just obsocure the username/password.

sandman420 Wed, 04/30/2008 - 15:03

I'll do a fresh debug when I get home tonight and hook it back up. that "term mon" command you mentioned...i assume i'm going



(config)#term mon


is that correct? again I apologize for the ignorance.

Thank you

Paolo Bevilacqua Wed, 04/30/2008 - 15:07

Hi, debug and "term mon" commands are issued from "normal" mode, aka exec, not config mode.

Also, please check what exact ISP settings you have with the linksys router, because dhcp and pppoe are mutually exclusive.

sandman420 Thu, 05/01/2008 - 08:14

I didn't have a chance to grab the debugs last night, will try again tonight.

I'm not sure what you are talking about by mutually exclusive on the pppoe and dhcp, as my router performs a pppoe login, however, the wan ip address DOES in fact get assigned via dhcp through the provider. Whenever you setup a linksys for pppoe, there is no option to statically put in your IP address, therefor, it obtains an address (which is known as dhcp), option examples being 1. static, 2. dhcp, 3. pppoe, etc. It is pppoe connection, and the ip is handed out dynamically.

Paolo Bevilacqua Thu, 05/01/2008 - 08:20


that would be a bit lengthy to explain, so just trust me this time, technically speaking PPP and DHCP are mutually exclusive. Thje confusion might arise because in common parlance, every time an address is dynamically assigned, that is referred as DHCP.

However, in both cases the ISP can assign you an address dynamically.

For this to happen with PPP, on the dialer interface, you will have "ip address negotiated".

For DHCP, on a LAN interface, or in some cases a BVI one, you will have "ip address dhcp".

The linksys choices you mentioned, are actually reflecting the same logic.

Let us know how do you progress with all that and good luck.

sandman420 Thu, 05/01/2008 - 20:49

Oh, you're not going to believe this. I don't.

I just went and started debugs and the term mon (which was already enabled), then connected dsl. After line came up, I sent a ping to and before it was done, I saw a bunch of text fly by and 2 successful pings. It was working! Don't know why all of a sudden this time it wanted to config changes? I am sending this reply from the connection! speed tests show this is getting up to the full 9 out of 10mbps my provider will give me. I was actually surprised to see 9Mbps.

I captured the whole event anyway and am attaching it. I was hoping you might be able to tell me what some of the info in the debug and the negotiation that happened means.

Thank you for you time.

Paolo Bevilacqua Fri, 05/02/2008 - 07:15

Hi, honest with you, I didn't looked at the debugs. I've seen enough already in my life :)

Guess all is good , thanks for the nice rating and good luck!


This Discussion