Routing Protocols Flashcards

What type of routing protocol is OSPF?

Answer: Link-State Interior Gateway Protocol

OSPF (Open Shortest Path First) is a link-state IGP that builds a complete topology map of the network using LSAs and calculates the shortest path using Dijkstra's SPF algorithm.

In Junos, what command enables OSPF on an interface?

Answer: set protocols ospf area 0.0.0.0 interface ge-0/0/0.0

In Junos, OSPF interfaces are configured by adding them to an OSPF area under the protocols hierarchy: 'set protocols ospf area [area-id] interface [interface]'.

What is the function of the OSPF Designated Router (DR) on a broadcast network?

Answer: To reduce the number of OSPF adjacencies by acting as a central point for LSA flooding on the broadcast segment

On multi-access broadcast segments (Ethernet), OSPF elects a DR and BDR to minimize the number of full adjacencies. All routers form Full adjacencies only with the DR and BDR, reducing LSA flooding.

What is the BGP attribute 'LOCAL_PREF' used for?

Answer: To influence outbound routing decisions within an AS by preferring routes with higher LOCAL_PREF values

LOCAL_PREF is a BGP well-known discretionary attribute shared among iBGP peers within the same AS. Higher LOCAL_PREF values are preferred, influencing which exit point is used for outbound traffic.

Which Junos command shows all routes redistributed from OSPF into the local routing table?

Answer: show route protocol ospf

'show route protocol ospf' in Junos operational mode filters the routing table to show only routes learned via OSPF, which includes redistributed routes if they are installed in the RIB.

What is the purpose of BGP route reflectors?

Answer: To eliminate the need for a full iBGP mesh by reflecting BGP routes between clients without requiring direct iBGP sessions between every router

Route reflectors (RR) solve the iBGP full-mesh scalability problem. In a full mesh, N routers need N*(N-1)/2 iBGP sessions. With RRs, client routers only peer with the RR, which reflects routes to all clients.