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Static routing configuration
Introduction
Static route
A static route is manually configured, but if a network’s topology is simple, you only need to configure
static routes for the network to function. The proper configuration and usage of static routes can improve
network performance and ensure bandwidth for important network applications.
The disadvantage of using static routes is that they cannot adapt to network topology changes. If a fault
or a topological change occurs in the network, the routes will be unreachable and the network breaks. In
the event of a fault or topological change, the network administrator has to modify the static routes
manually.
The term
router
in this document refers to a router in a generic sense or a Layer 3 switch.
Default route
If the packet’s destination address fails to match any entry in the routing table, the packet is discarded.
After a default route is configured on a router, any packet whose destination IP address matches no entry
in the routing table can be forwarded to a designated upstream router.
A router selects the default route only when it cannot find any matching entry in the routing table.
•
If the destination address of a packet fails to match any entry in the routing table, the router selects
the default route to forward the packet.
•
If there is no default route and the destination address of the packet fails to match any entry in the
routing table, the packet will be discarded and an ICMP packet will be sent to the source to report
that the destination or the network is unreachable.
You can configure a default route with both the destination and mask being 0.0.0.0. The router forwards
any packet whose destination address fails to match any entry in the routing table to the next hop of the
default static route.
Application environment of static routing
Before configuring a static route, you need to know the following concepts:
•
Destination address and mask:
In the
ip route-static
command, an IPv4 address is in dotted decimal format and a mask can be
either in dotted decimal format or in the form of mask length (the number of consecutive 1s in the
mask).
•
Output interface and next hop address:
