CCIE Blog

Hi Brian,

I am using dialer profiles for ISDN and I want protocol broadcasts such as RIP to be sent out accross the ISDN link. I tried to find the command that allows me to configure broadcast but the dialer interfaces do not accept the dialer map command. How do I accomplish this?

When using dialer profiles, dialer interfaces are point-to-point, therefore there is no need for protocol mappings. IP broadcasts should not have any trouble being sent across the interface as long as you have an IP address configured on the interface. Dialer maps are only used on dialer interfaces when using rotary groups. Dialer profiles are for when you have a single physical interface, but multiple destinations to dial. Rotary groups are for when you have multiple physical interfaces, but one destination to dial.

Unlike PAP, CHAP does not actually send a password over the line. Instead, a hash value made up of the password and magic number is sent. Unless the hash matches from both authenticating parties, authentication is not successful.

By default, the router sends it’s hostname for authentication when using chap. The router on the other side does a lookup in its local database, radius server, or tacacs server, and finds the password that is paired with that username. If there is no matching username in the database, the password specified with the interface level command ‘ppp chap password’ is used as the default password.

Suppose you have a central office that has many remote clients dialing into it. If you don’t want to create an entry in the user database for each remote client, you can just specify a default password with ‘ppp chap password’. As long as the remote clients have an entry for the central site in their user database, authentication will be successful.

“async mode dedicated” is strictly for PPP and SLIP connections. “async mode interactive”, on the other hand, can be used for PPP, SLIP, ARAP, along with EXEC access to the router. Suppose you’re dialing into the router’s AUX port to access the CLI. In this case you want interactive mode. If you’re dialing into the router strictly for a PPP connection, use dedicated mode.

When using interactive mode, you can also use the command “autoselect” on the line to have the router automatically determine whether you want a PPP connection or an EXEC connection.

“async default routing” enables routing on an async interface by default. This means when you dial into the interface, routing is already set up. “async dynamic routing” means that the user must manually initiate the PPP session from the EXEC mode. “async dynamic routing” would be used if you have an “async mode interactive” for which you want EXEC access, and then want to call a PPP session.

Under normal use, you would pair “async mode dedicated” along with “async default routing” when running PPP over a dial-in connection. “async mode interactive” will be used to get remote access to the router via a modem attached to the AUX port. You most likely would not use “async dynamic routing”, since you can just say “autoselect PPP” if you want interactive EXEC and PPP access.