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Chapter 16 - Configuring Dynamic Routing
Chapter 16 - Configuring Dynamic Routing
Introduction
This chapter familiarizes the user with:
• Enabling The Dynamic Routing Suite
• Enabling And Starting OSPF and RIP
• Configuring OSPF and RIP
• Obtaining OSPF and RIP Status
• OSPF and VRRP
Quagga, RIP and OSPF
Dynamic routing is provided by the Quagga suite of routing protocol daemons.
Quagga provides three daemons for managing routing, the core, ripd and ospfd.
The core daemon handles interfacing with the kernel to maintain the router's routing
table and to check link statuses. It tells RIP and OSPF what state links are in, what
routes are in the routing table, and some information about the interfaces.
The ripd and ospfd daemon handles communications with other routers using the
RIPv2 and OSPFv2 protocol, decides which routers preferred to forward to.
In complex legacy networks, both RIP and OSPF may be active on the same router at
the same time. Usually, one on them is employed.
RIP Fundamentals
The Routing Information Protocol determines the best path for routing IP traffic over
a TCP/IP network based on the number of hops between any two routers. It uses the
shortest route available to a given network as the route to use for sending packets to
that network.
The RuggedRouter RIP daemon (ripd) is an RFC1058 compliant implementation of
RIP support RIP version 1 and 2. RIP version 1 is limited to obsolete class based
networks, while RIP version 2 supports subnet masks as well as simple authentication
for controlling which routers to accept route exchanges with.
RIP uses network and neighbor entries to control which routers it will exchange routes
with. A network is either a subnet or a physical interface (it must to be a broadcast
capable interface). Any router that is part of that subnet or connected to that interface
may exchange routes. A neighbor is a specific router to exchange routes with
specified by its IP address. For point to point links (T1/E1 links for example) one
must use neighbor entries to add other routers to exchange routes with. The
maximum number of hops between two points on a RIP network is 15, placing a limit
on network size.
Link failures will eventually be noticed although it is not unusual for RIP to take
many minutes for a dead route to disappear from the whole network. Large RIP
networks could take over an hour to converge when link or route changes occur. For
fast convergence and recovery, OSPF is a much better choice. RIP is a fairly old
routing protocol and has mostly been superseded by OSPF.
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