3Com Switch 8800 Advanced Software V5 Configuration Guide

260 CHAPTER 26: STATIC ROUTING CONFIGURATION
Application
Environment of Static
Routing
Before configuring a static route, you need to know the following concepts:
1 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
digits of consecutive 1s in the mask).
2 Output interface and next hop address
While configuring a static route, you can specify either the output interface or the
next hop address depending on the specific occasion. The next hop address can
not be a local interface IP address; otherwise, the route configuration will not take
effect.
In fact, all the route entries must have a next hop address. When forwarding a
packet, a router first searches the routing table for the route to the destination
address of the packet. The system can find the corresponding link layer address
and forward the packet only after the next hop address is specified.
When specifying the output interface, note that:
■ If the output interface is a NULL0 or loopback interface, there is no need to
configure the next hop address.
■ You are not recommended to specify a broadcast interface (such as an Ethernet
interface, virtual template, or VLAN interface) as the output interface, because
a broadcast interface may have multiple next hops. If you have to do so, you
must specify the corresponding next hop for the output interface.
3 Other attributes
You can configure different preferences for different static routes so that route
management policies can be applied more flexibly. For example, specifying the
same preference for different routes to the same destination enables load sharing,
while specifying different preferences for these routes enables route backup.
You can also enable bidirectional forwarding detection (BFD) to implement fast
detection on the next hops of static routes. When a next hop is unreachable, the
system can switch to a backup route instantly.
Configuring a Static
Route
Configuration
Prerequisites
Before configuring a static route, you need to finish the following tasks:
■ Configure the physical parameters for related interfaces
■ Configure the link-layer attributes for related interfaces
■ Configure the IP addresses for related interfaces
Configuration Procedure Follow these steps to configure a static route: