Ip routing basics, Ip routing overview, Routing table – H3C Technologies H3C SR8800 User Manual
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IP routing basics
IP routing overview
Upon receiving a packet, a router determines the optimal route based on the destination address and
forwards the packet to the next router in the path. When the packet reaches the last router, it then
forwards the packet to the destination host.
Routing provides the path information that guides the forwarding of packets.
Routes can be divided into the following categories by destination:
•
Network route—The destination is a network. The subnet mask is less than 32 bits.
•
Host route—The destination is a host. The subnet mask is 32 bits.
Based on whether the destination is directly connected to the router, routes can be divided into the
following types:
•
Direct routes—The destination is directly connected to the router.
•
Indirect routes—The destination is not directly connected to the router.
Routing table
A router selects optimal routes from the routing table, and sends them to the forwarding information base
(FIB) table to guide packet forwarding. Each router maintains a routing table and a FIB table.
Routes in a routing table can be divided into the following categories by origin:
•
Direct routes—Routes discovered by data link protocols, also known as “interface routes.”
•
Static routes—Routes manually configured. Static routes are easy to configure and require less
system resources. They work well in small and stable networks. Static routes cannot adjust to
network changes. You must manually configure the routes again whenever the network topology
changes.
•
Dynamic routes—Routes that are discovered dynamically by routing protocols.
Each entry in the FIB table specifies a physical interface that packets destined for a certain address
should go out to reach the next hop—the next router—or the directly connected destination.
NOTE:
For more information about the FIB table, see
Layer 3—IP Services Configuration Guide.
You can view the brief information of a routing table by using the display ip routing-table command.
For example:
<Sysname> display ip routing-table
Routing Tables: Public
Destinations : 7 Routes : 7
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.0/24 Direct 0 0 1.1.1.1 GE3/1/1