OSPF DR

[jm2753]

When a new router is added on to an established network running OSPF is the Designated Router selection process reinitiated?

[Richard Burts]

When a new router joins an established network (assuming that a DR and a BDR have already been elected) it does not cause the DR selection process to process again. Joining a network is not a pre-emptive act that allows the new router to immediately become DR or BDR.

HTH

Rick

[pkhatri]

Hi,

Just to add to Rick's post, when a new router is added to a network (with a DR/BDR already elected), the router *will* carry out a DR election. However, the result of this election will be that the current DR/BDR will be re-elected.

The following occurrences cause the DR election to be run (from RFC2328):

o Bidirectional communication has been established to a neighbor. In other words, the state of the neighbor has transitioned to 2-Way or higher.

o There is no longer bidirectional communication with a neighbor. In other words, the state of the neighbor has transitioned to Init or lower.

o One of the bidirectional neighbors is newly declaring itself as either Designated Router or Backup Designated Router. This is detected through examination of that neighbor's Hello Packets.

o One of the bidirectional neighbors is no longer

declaring itself as Designated Router, or is no longer declaring itself as Backup Designated Router. This is again detected through examination of that neighbor's Hello Packets.

o The advertised Router Priority for a bidirectional neighbor has changed. This is again detected through examination of that neighbor's Hello Packets.

Hope that helps - pls rate the post if it does.

Paresh