which routers does the backup designated router (BDR) form adjacencies to?

In IS-IS networks, which routers does the backup designated router (BDR) form adjacencies to?

In IS-IS networks, which routers does the backup designated router (BDR) form adjacencies to?

A.
Only to the DR.

B.
The BDR only becomes adjacent when the DR is down.

C.
To all routers.

D.
There is no BDR in IS-IS.

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Keith

Keith

…”A selected router is not guaranteed to remain the DIS. Any adjacent IS with a higher priority automatically takes over the DIS role. This behavior is called preemptive, There is no backup DIS. Contrast this with OSPF, where the DR and backup designated router (BDR) are selected, and the other routers on the LAN establish full adjacencies with the DR and BDR. In case of DR failure, the BDR is promoted to DR and a new BDR is elected.”
http://anetworkerblog.com/2009/09/12/dis-on-isis/

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