Core Layer

Different IEEE Standard

:

Distance Vector Concepts:

1) Routers adds directly connected subnets to their routing table even without routing protocol

2)Routers send routing updates out on interface to advertise routing information about the directly connected routes and that learned from other  routers.

3)Routers  Listen routing updates from the neighboring routers so that they can learn new routes.

4)Routing information includes subnet and metric.

5) Broadcast & Multicasts

6) sends periodic updates and expect to receive periodic updates

7) Failure to receive updates in a timely manner results in the removal of the routes previously learned from that neighboring routers.

8) A router assumes that, for a route advertised by router X, the next hop router in that route is Router X.

Route Poisoning

Reduce the chance of  loops (occurs due to up and down, up and down status of the link)

Advertises Infinite Metric for the failed link/route.

Split Horizon

Prevents counting to infinity and adding poison reverse ensures that all routers know for sure that the route has failed.

RIP and IGRP use the Split Horizon with Poison Reverse.

Hold Down Timer:

Link State Routing:

Split Horizon

Hold down timer

RIP

IGRP

OSPF

EIGRP

Nat & Pat

Frame Relay

ISDN & DDR