3Com 5500 SI - Switch - Stackable, Configuration Manual

Page: 224 / 686

224 C
HAPTER
16: IP R
OUTING
P
ROTOCOL
O
PERATION
2 Configure the static route for Ethernet Switch B
[Switch B] ip route-static 1.1.2.0 255.255.255.0 1.1.3.1
[Switch B] ip route-static 1.1.5.0 255.255.255.0 1.1.3.1
[Switch B] ip route-static 1.1.1.0 255.255.255.0 1.1.3.1
3 Configure the static route for Ethernet Switch C
[Switch C] ip route-static 1.1.1.0 255.255.255.0 1.1.2.1
[Switch C] ip route-static 1.1.4.0 255.255.255.0 1.1.3.2
4 Configure the default gateway of the Host A to be 1.1.5.2
5 Configure the default gateway of the Host B to be 1.1.4.1
6 Configure the default gateway of the Host C to be 1.1.1.2
Using this procedure, all the hosts or switches in Figure 54 can be interconnected in
pairs.
Troubleshooting Static
Routes
The Switch 5500 is not configured with the dynamic routing protocol enabled. Both
the physical status and the link layer protocol status of the interface are enabled, but
the IP packets cannot be forwarded normally.
Troubleshooting:
■
Use the
display ip routing-table protocol static
command to view
whether the corresponding static route is correctly configured.
■
Use the
display ip routing-table
command to view whether the
corresponding route is valid.
RIP
Routing Information Protocol (RIP) is a simple dynamic routing protocol, that is
Distance-Vector (D-V) algorithm based. It uses hop counts to measure the distance to
the destination host. This is called the routing cost. In RIP, the hop count from a router
to its directly connected network is 0; the hop count to a network which can be
reached through another router is 1; and so on. To restrict the time to converge, RIP
prescribes that the cost value is an integer ranging from 0 and 15. A hop count equal
to or exceeding 16 is defined as infinite, which indicates that the destination network
or the host is unreachable.
RIP sends a routing refresh message every 30 seconds. If no routing refresh message is
received from a network neighbor in 180 seconds, RIP tags all routes of the network
neighbor as unreachable. If no routing refresh message is received from a network
neighbor in 300 seconds, RIP removes the routes of the network neighbor from the
routing table.
To improve network performances and avoid routing loops, RIP supports split horizon,
poison reverse, and allows importing of routes discovered by other routing protocols.
Each router that is running RIP manages a route database, which contains routing
entries to all the reachable destinations in the network. These routing entries contain
the following information:
■
Destination address—The IP address of a host or network.
■
Next hop address—The address of the next router that an IP packet will pass
through for reaching the destination.
■
Output interface—The interface through which the IP packet should be
forwarded.