Friday, April 2, 2010

Master/slave or DR/BDR election:

This is a second election process in OSPF to exchange information without collision in the network.

Parameters for election process are
1. Priority (by default the priority is 1) - first preference.
2. Highest router-id - second preference.

Master/Slave election takes place in point-to-point nature i.e, when routers connected using serial interface.
Master router will collect the information about all the router with a Area, and then it will exchange the information to all other router in the network, thus collision can be avoided. Slave router will also have the same information what master has but it will act as normal router performing its work only.
DR/BDR (Designated Router Back-up Designated Router) election takes place in broadcast nature i.e., when routers connected using Ethernet interface.
Master router will collect the information about all the router with a Area, and then it will exchange the information to all other router in the network, thus collision can be avoided. BDR is a back-up to DR whereas when DR goes down immediately BDR will become DR to continue the process. The remaining router will be DR others by performing their work only.

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