9. Advanced OSPF Flashcards
What is the name for area zero?
The backbone, all areas must connect to area 0
What are ABRs (Area Border Routers)?
Routers that are connect to area 0 and a different area
What is an area ID?
32-bit field that can be formatted in decimal or dotted decimal. One router can choose decimal the neighbor can use dotted decimal
What is an intra-area route?
Routes learned from within the OSPF area. Can be found marked with an O in the routing table
What is an inter-area route?
Routes learned from other OSPF areas, Can be found marked with O IA in the routing table
What are the six OSPF LSA type for IPv4 routing?
1 - Router LSA 2 - Network LSA 3 - Summary LSA 4 - ASBR summary LSA 5 - AS external LSA 7 - NSSA
Why does OSPF use a sequence number in LSAs?
To overcome problems caused by delay. The originating router increments the sequence number when the LSA is send out. The receiving routers checks the sequence number. If it his higher than the one in the LSDB it processes, lower it discards
What is the LSA age for?
Every LSA inclused an age that will increment by 1 every second. At 1800 sec the originating router sends a new LSA with age 0. At 3600 the LSA gets removed
What is the command the view the LSA type on a router?
show ip ospf database
What is the command to view detaild Type 3 LSA information?
show ip ospf database summary
What is the command to view detaild Type 2 LSA information?
show ip ospf database network
What is the command to view detaild Type 1 LSA information?
show ip ospf database router
What is the advertising router for type 3 LSA?
The last ABR router that the type 3 is created on
What is the path selection priority logic?
Intra-area - Type 1 is always preferred over type 3
Internarea
External routes
What is the default number for ECMP routes?
4
