TMS zl Management and Configuration Guide ST.1.1.100430
9-12
Routing
Dynamic Routing
■ When routers send and receive updates and hellos—To lower overhead
and conserve bandwidth, you can alter how often routers send certain
messages.
You can fine-tune the routing protocol to best fit your router’s role in your
network topology. Some protocols provide more flexibility in implementation
than others. In general, OSPF provides more options for customizing adver-
tisements for your particular network environment. However, the configura-
tion for that protocol can be more complex than the configuration for RIP.
Before you implement a routing protocol on your network, you should evalu-
ate the options each protocol provides and then determine which one will
work best for your network environment. Table 9-2 compares how RIP and
OSPF control basic options. You can learn about each protocol in more detail
in the overview for the configuration section on that protocol. See “RIP” on
page 9-15 and “OSPF” on page 9-27.
Table 9-2. RIP and OSPF Comparison
Option RIP OSPF
Metric computation and
route selection
Number of hops to the destination. • Inverse bandwidth
• Type of service (ToS) (rarely used)
Information in updates Routers send the complete RIP routing
table.
Different types of LSAs include different
information:
• A link and its status:
– link to a network
– link to another router
• Router ID of every router in a multi-access
network
• Summary route to a range of networks in an
area (sent by ABRs)
• Route to autonomous system border router,
or ASBR (sent by ABRs)
• External routes or default route for external
traffic (sent by ASBRs)
The routers and router
interfaces that send and
receive updates
• All router interfaces on RIP networks.
• The interface that receives a route
advertises it as unreachable (split
horizon with poison reverse).
• Passive interfaces receive updates
but do not send them.
• In point-to-point networks, neighboring
routers exchange LSAs.
• In multi-access networks, all routers send
LSAs to a DR and backup DR (BDR) and
receive LSAs from a DR.
• ABRs send route summaries into stub areas.