3Com Switch 4500 26-Port User Manual

Static Routes 107
The following routes are static routes:
■ Reachable route — The IP packet is sent to the next hop towards the
destination. This is a common type of static route.
■ Unreachable route — When a static route to a destination has the reject
attribute, all the IP packets to this destination are discarded, and the originating
host is informed that the destination is unreachable.
■ Blackhole route — If a static route to a destination has the blackhole attribute,
all the IP packets to this destination are discarded, and the originating host is
not informed.
The attributes reject and blackhole are usually used to control the range of
reachable destinations for the router, and to help troubleshoot the network.
Default Route
The default route is also a static route. The default route is used only when no
suitable routing table entry is found. In a routing table, the default route is in the
form of the route to the network 0.0.0.0 (with the mask 0.0.0.0). You can
determine whether a default route has been set by viewing the output of the
display ip routing-table command. If the destination address of a packet fails
to match any entry of the routing table, the router selects the default route to
forward this 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 is discarded, and an
Internet Control Message Protocol (ICMP) packet is sent to the originating host to
indicate that the destination host or network is unreachable.
In a typical network that consists of hundreds of routers, if you used multiple
dynamic routing protocols without configuring a default route then significant
bandwidth is consumed. Using the default route can provide appropriate
bandwidth for communications between large numbers of users.
Configuring Static
Routes
Static route configuration tasks are described in the following sections:
■ Configuring a Static Route
■ Configuring a Default Route
■ Deleting All The Static Routes
■ Displaying and Debugging Static Routes
Configuring a Static Route
Perform the following configurations in System View.
Tab le 100 Configuring a static route
Operation Command
Add a static route ip route-static ip_address { mask | mask_length } {
interface_type interface_number | gateway_address }
[ preference value ] [ reject | blackhole ]
Delete a static
route
undo ip route-static ip_address { mask | mask_length
} [ interface_type interface_number |
gateway_address ] [ preference value ] [ reject |
blackhole ]

3Com Switch 4500 26-Port Specifications

General

Brand	3Com
Model	Switch 4500 26-Port
Category	Switch
Language	English