frame-relay lmi-type autosensing

smcclenaghan

I'm curious; Odom's ICND2 book mentions that the default behavior for frame-relay is that LMI type is automatically sensed.

However, on one of the Boson test questions, the answer implies that a Cisco router and a 3rd party router will not be able to communicate unless both are set to lmi-type=ansi. (I say 'implied', it doesn't come right out and say this).

In my lab, I've only got Cisco routers.

Does anyone have first hand experience with this? In a frame-relay circuit with cisco and non-cisco routers, will the LMI type be automatically sensed as Odom says? Or must I configure lmi-type=ansi?

Thanks for any help.

gadav478

I believe that when LMI type is not configured on a router, it actually sends all three types of LMI. The frame relay switch replies with the one that is accepted (is configured to communicate using) and the router autosenses to the reply.

Here a link to some information: Configuring the LMI Type on a Frame Relay Interface > Cisco Frame Relay Configurations

smcclenaghan

Awesome info. Thanks, gadav478. Seems to be another case of Boson being slightly off, but still achieving it's purpose of teaching me a ton.

I've yet to see Odom's books be wrong on anything. Figure I'd stop doubting it by now, huh?

gadav478

Not until I read Odom throughly did I pass my CCNA. Food for thought...

DCD

In the old day's you had to get the LMI type from the provider based on his equipment. With the autosense the router sends out all three LMI types. The router then waits for one of the LMI types from the Frame-relay provider (DCE). When the router sees the response to its LMI message, Then the router will send only the LMI type it received from the DCE.