Ip Routing Basics; Routing Table - HPE FlexNetwork HSR6800 Configuration Manual

IP routing basics

IP routing directs the forwarding of IP packets on routers based on a routing table. This book focuses
on unicast routing protocols. For more information about multicast routing protocols, see IP Multicast
Configuration Guide.

Routing table

A router maintains at least two routing tables: one global routing table and one forwarding
information base (FIB). The FIB table contains only the optimal routes, and the global routing table
contains all routes. The router uses the FIB table to forward packets. For more information about the
FIB table, see Layer 3—IP Services Configuration Guide.
Routes can be classified by different criteria, as shown in
Table 1 Categories of routes
Criterion
Destination
Whether the
destination is directly
connected
Origin
Static routes are easy to configure and require less system resources. They work well in small and
stable networks. In networks where topology changes might occur frequently, using a dynamic
routing protocol is better.
To view brief information about a routing table, use the display ip routing-table command, as
shown in the following example:
<Sysname> display ip routing-table
Routing Tables: Public
Destinations : 7
Destination/Mask
1.1.1.0/24
2.2.2.0/24
80.1.1.0/24
...(Part of the output information is not shown)
A route entry includes the following key items:
•
Destination—IP address of the destination host or network.
•
Mask—Mask length of the IP address.
Categories
•
Network route—Destination is a network. The subnet mask is less than 32
bits.
•
Host route—Destination is a host. The subnet mask is 32 bits.
•
Direct route—Destination is directly connected.
•
Indirect route—Destination is indirectly connected.
•
Direct route—A direct route is discovered by the data link protocol on an
interface, and is also called an "interface route."
•
Static route—A static route is manually configured by an administrator.
•
Dynamic route—A dynamic route is dynamically discovered by a routing
protocol.
Routes : 7
Proto Pre Cost
Direct 0 0
Static 60 0
OSPF 10 2
1
Table 1.
NextHop Interface
1.1.1.1 Eth1/1
12.2.2.2 Eth1/2
80.1.1.1 Eth1/3