CCNA 3 chapter 10.docx - CCNA 3 – Chapter 10: OSPF Tuning...

CCNA 3 – Chapter 10: OSPF Tuning and Troubleshooting
 OSPF Network types:
o Point-to-point
o Broadcast multiaccess
o Nonbroadcast multiaccess (NBMA)
o Point-to-multipoint
o Virtual links
 Multiaccess networks create two challenges regarding the flooding of
OSPF LSAs.
o Creation of multiple adjacencies
o Extensive flooding of LSAs
 On multiaccess networks, OSPF elects a DR to be the collection and
distribution point for LSAs sent and received.
o A BDR is also elected for when the DR fails.
o All non-DR and BDR routers become DROTHER and only form full
adjacencies with the DR and BDR in the network.
 DR is the router with the highest router ID
 BDR is the router with the 2nd highest router ID
 Election of DR/BDR
o 1. Highest interface priority 0-255, default priority is 1.
o 2. Router ID
o 3. Highest loopback IP number
o 4. Highest interface IP number
o If the interface priority is set to 0, it will not be part of the
election at all.