Link-State Routing Protocols - Routing Protocols and Concepts - page 480

Table 10-3 SPF Tree for R3

Destination Shortest Path Cost

R1 LAN R3 to R4 to R1 22

R2 LAN R3 to R5 to R2 27

R4 LAN R3 to R4 12

R5 LAN R3 to R5 7

Table 10-4 SPF Tree for R4

Destination Shortest Path Cost

R1 LAN R4 to R1 12

R2 LAN R4 to R1 to R2 22

R3 LAN R4 to R3 12

R5 LAN R4 to R3 to R5 17

Table 10-5 SPF Tree for R5

Destination Shortest Path Cost

R1 LAN R5 to R3 to R4 to R1 27

R2 LAN R5 to R2 22

R3 LAN R5 to R3 7

R4 LAN R5 to R3 to R4 17

Link-State Routing Process

All routers in our topology will complete the following generic link-state routing process to reach a
state of convergence:

Each router learns about its own links, its own directly connected networks. This is done by
detecting that an interface is in the up state.

1.

Each router is responsible for meeting its neighbors on directly connected networks. Similar to
Enhanced Interior Gateway Routing Protocol (EIGRP), link-state routers do this by exchanging
Hello packets with other link-state routers on directly connected networks.

2.

Each router builds a link-state packet (LSP) containing the state of each directly connected link.
This is done by recording all the pertinent information about each neighbor, including neighbor
ID , link type , and bandwidth .

3.

Each router floods the LSP to all neighbors, who then store all LSPs received in a database .
Neighbors then flood the LSPs to their neighbors until all routers in the area have received the
LSPs. Each router stores a copy of each LSP received from its neighbors in a local database .

4.

Each router uses the database to construct a complete map of the topology and computes the
best path to each destination network.

5.