Selection of DR & BDR Router in OSPF network topology

DR stand for designated router,BDR stand for backup designated router.This terminilogy is used in OSPF network in Point to Multipoint network topology.DR is core router in a network or Domain,which contain whole information of the network.topology table,neighbor table,routing table.It is used to forward LSA2 information while making any adjacency with newely placed router in the network.or spready topology changes in the network with the other router.BDR used as a backup router for DR.
Criteria for the selection of DR & BDR:---

1)  Priority Basis
2)  Highest IP Address of the network.


a)  Priority Basis :-- 
 Priority is 8 bit information ranges 1-255  Lower priority win the battle for DR and second lower priority win for BDR.Default priority is 1.    0 priority means is cannot fight for DR & BDR selection.

b)   Highest IP Address basis :--

      If the default priority will equal then highest ip address win the battle for DR. egample  there are router whose priority is 1 by default and the network is 192.168.1.0/24 the 192.168.1.254/24 IP will win the battle for DR.


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