ISDN + PPP question

polm

If ISDN is enabled on a specific interface, and PPP encapsulation is defined on that interface to use CHAP, do standard, global, username hostname passsword, settings not apply to the ISDN's PPP connection ?

Is the username defined in the "dialer map" command , the only username that can authenticate through the ISDN's PPP connection ?

knownasthatguy

You have to be careful when you put ISDN and PPP together. They are very two seperate protocols. For what I know about ISDN, the only negotiation is on the D-channel. Once the signaling is done, the Bearer channels setup their connection. Once the Bearer channels are done setting up, then PPP will perform its setup, i.e. chap/pap. I dont believe that the Dialer setup has anything do with ISDN. From what I have studied of both protocols, I do believe this to be the answer. Remember to keep apples with apples and oranges with oranges.

forbesl

knownasthatguy wrote:

You have to be careful when you put ISDN and PPP together. They are very two seperate protocols. For what I know about ISDN, the only negotiation is on the D-channel. Once the signaling is done, the Bearer channels setup their connection. Once the Bearer channels are done setting up, then PPP will perform its setup, i.e. chap/pap. I dont believe that the Dialer setup has anything do with ISDN. From what I have studied of both protocols, I do believe this to be the answer. Remember to keep apples with apples and oranges with oranges.

ISDN isn't a protocol, it's a system of digital phone connections, and there is no problem running PPP over ISDN B-channels. Matter of fact, there is an RFC specifically for PPP over ISDN:
http://www.faqs.org/rfcs/rfc1618.html

knownasthatguy

I know ISDN and PPP are compatible, but I dont think there is a Q.931 function that does authentication for PPP. PPP does the CHAP and PAP. What I was trying to indicate is that the B channels are merely a xport system while the D channel is the signaling channel. After ISDN is done, PPP does it thing. The question:
Is the username defined in the "dialer map" command , the only username that can authenticate through the ISDN's PPP connection
Indicates that the dialer map contains the requirements for the PPP auth connection. From what I have studied of ISDN on the cisco, the dialer map is only concerned with local loop telephony signaling and connection protocols. The PPP auth settings should be done at the PPP menu options.

nethead

The ISDN connection will come up first and any q921/q931 debugging will show the negotiation for the ISDN at layers 2&3. Once the ISDN is UP then PPP will be able to run across this connection, its first function usually being authentication. If the line is connecting and then dropping but you see nothing when debugging q921/q931 then it is probably a ppp authentication issue as this wouldn't be seen under these debug commands. To see problems with ppp you would need to "debug ppp ....."

PPP authentication can either use a username (hostname) specifically configured on the interface using the ppp configuration commands or by default it will use a username/password combination configured on the router.

Method 1:

RouterA:
hostname routA
username routB password test

RouterB:
hostname routB
username routA password test

Method 2:
RouterA:
hostname routA
username UserB password test
interface bri1/1
ppp chap hostname UserA

RouterB:
hostname routB
username UserA password test
interface bri1/1
ppp chap hostname UserB

I hope this helps.

polm

Here is the syntax for the "dialer map" command :

dialer map protocol next-hop-address b]name[/b] [i]hostname[/i b]speed 56 ? 64[/b b]broadcast[/b dialer-string

Where:

-name hostname is the remote device's name. This name is used for PPP authentication (CHAP or PAP) or ISDN calls supporting caller ID.

knownasthatguy

at what point does the spid come into play?

forbesl

at what point does the spid come into play

If the carrier assigns you a spid, that comes into play during the initial ISDN negotiation for the connection. Like nethead stated, the ISDN connection is negotiated and established first, then PPP cranks up.

http://www.cisco.com/en/US/tech/tk801/tk379/technologies_configuration_example09186a0080094091.shtml

http://www.cisco.com/en/US/tech/tk801/tk379/technologies_configuration_example09186a0080094abd.shtml