OSPF Series 11: Everything on Redistribution: Part 2- Redistribution into OSPF, Pitfall of Redistribution (Administrative Distance, Route Feedback)

Everything on Redistribution: Part 2- Redistribution into OSPF, Pitfall of Redistribution (Administrative Distance, Route Feedback)

 

Redistributing into OSPF

OSPF is a standardized Link-State routing protocol that uses cost (based on bandwidth) as its link-state metric. An OSPF router performing redistribution automatically becomes an ASBR

OSPF Series 10: Everything on Redistribution: Part 1- Basics, RIP, IGRP, EIGRP, Static and Connected

Everything on Redistribution- Basics, RIP, IGRP, EIGRP, Static and Connected

Route Redistribution Basics

It is preferable to employ a single routing protocol in an internetwork environment, for simplicity and ease of management. Unfortunately, this is not always possible, making multi-protocol environments common.

Route Redistribution allows routes

OSPF Series 9: Route Filtering and Route-Maps

Prefix-Lists

Prefix-lists are used to match routes as opposed to traffic. Two things are matched:

• The prefix (the network itself)

• The prefix-length

OSPF Series 8: Prefix Lists

Prefix Lists

Example 1)

access-list 1 permit 1.2.3.0 0.0.0.255

ip prefix-list LIST permit 0.0.0.0/0 le 32

This means:

Check the first 0 bits of the prefix 0.0.0.0 The subnet mask must be less than or equal to 32

OSPF Series 7: Example of OSPF Path Preferences, Troubleshooting neighborship stuck in various OSPF States

SCENARIO: Path Preferences:

• Configure Router-IDs on each router

• COnfigure IP address of interfaces in each router and add them using network command of OSPF

• Note: there is no need to configure static routes on MT708 as both the links are directly connected. MT708 doesn’t run OSPF.

• (On MT704,

OSPF Series 5: Link State Updates, Advertisements and Message Formats

LS Updates (and Advertisements):

• Note there is no LS Advertisement packet as such. Link State Update is the type of OSPF packet that carries many LS advertisements

• Each Link State Update packet carries a collection of link state advertisements one hop further from its origin. Several link-state advertisement may be included in a single LS Update packet. If any router notices a change in its networks, it sends that particular type of LS Update to the DR and BDR.

• Link State Update (carries Advertisements), it’s format is as given below: