H3C S3610-28P Operation Manual page 329

Operation Manual – Routing Overview
H3C S3610&S5510 Series Ethernet Switches
II. Contents of a routing table
A routing table includes the following key items:
Destination address: Destination IP address or destination network.
Network mask: Specifies, in company with the destination address, the address of
the destination network. A logical AND operation between the destination address
and the network mask yields the address of the destination network. For example,
if the destination address is 129.102.8.10 and the mask 255.255.0.0, the address
of the destination network is 129.102.0.0. A network mask is made of a certain
number of consecutive 1s. It can be expressed in dotted decimal format or by the
number of the 1s.
Outbound interface: Specifies the interface through which the IP packets are to be
forwarded.
IP address of the next hop: Specifies the address of the next router on the path. If
only the outbound interface is configured, its address will be the IP address of the
next hop.
Priority for the route. Routes to the same destination but having different nexthops
may have different priorities and be found by various routing protocols or manually
configured. The optimal route is the one with the highest priority (with the smallest
metric).
Routes can be divided into two categories by destination:
Subnet routes: The destination is a subnet.
Host routes: The destination is a host.
Based on whether the destination is directly connected to a given router, routes can be
divided into:
Direct routes: The destination is directly connected to the router.
Indirect routes: The destination is not directly connected to the router.
To prevent the routing table from getting too large, you can configure a default route. All
packets without matching entry in the routing table will be forwarded through the default
route.
In Figure
Router G resides in three networks and therefore has three IP addresses for its three
physical interfaces. Its routing table is shown on the right of the network topology.
1-1, the IP address on each cloud represents the address of the network.
1-2
Chapter 1 IP Routing Overview