Challenge handshake authentication protocol (CHAP)

Two-factor authentication

MD5 message digest authentication

Extensible authentication protocol (EAP)

IS-IS uses the concept of level-1 and level-2 routers to implement hierarchy.

In IS-IS, routers are associated with an area, not the interfaces.

A router becomes level-2 when it is associated with the backbone area.

A level-1 router forwards traffic to other areas through the nearest level-1/level-2 router.

Control messages are transmitted inside UDP packets.

Control messages are transmitted inside IP multicast packets.

Control messages are encapsulated inside Ethernet multicast frames.

Control messages are encapsulated inside IP packets sent to the subnet broadcast address.

CSNP messages are used to maintain consistency in the link-state databases of neighboring routers,

CSNP messages are exchanged by routers before an adjacency is formed between them.

Separate CSNP messages are used to describe the contents of the level-1 and level-2 link-state databases.

CSNP messages are used to describe the full list of LSPs in a router's link-state database.

Router R4 will have a route to router R6's system IP address with router R3 as the next-hop.

Router R4 will have a default route with router R2 as the next-hop.

Router R4 will have a default route with router R3 as the next-hop.

Router R4 will not have a matching entry in its routing table for router R6's system IP address.