3Com 4007, Implementation Manual, Page: 372 / 684

372 C
HAPTER
16: IP R
OUTING
Enable IP Routing To enable IP routing, use the
ip routing
command on the
Administration Console or use the IP Configuration form in the Web
Management software. By default, IP routing is disabled on the Multilayer
Switching Module.
You can use the Routing Information Protocol (RIP) or the Open Shortest
Path First (OSPF) protocol to take advantage of routing capabilities. RIP is
discussed in this chapter; OSPF is discussed in
Chapter 19 .
Administering IP
Routing
Keep these points in mind while you administer the IP network:
■
Flush the ARP cache regularly if you set the age time to 0.
■
Set up a default route.
The Multilayer Switching Module uses the default route to forward
packets that do not match any other routing table entry. You may
want to use the default route in place of routes to numerous
destinations that all have the same gateway IP address. If you do not
use a default route, ICMP is more likely to return an
address not
found
error.
■
Before you can define static routes, you must define at least one IP
interface. See “Defining an IP Interface” earlier in this chapter for
more information. Remember the following guidelines:
■
Static routes remain in the routing table until you remove them or
the corresponding interface.
■
Static routes take precedence over dynamically learned routes to
the same destination.
■
Static routes are included in periodic RIP updates sent by your
Layer 3 module.
Address Resolution
Protocol (ARP)
ARP is a low-level protocol that locates the MAC address that
corresponds to a given IP address. This protocol allows a host or router to
use IP addresses to make routing decisions while it uses MAC addresses
to forward packets from one hop to the next.