Static route types

You can configure the following types of static IP routes:

Standard

The static route consists of a destination network address or host, a corresponding network mask, and the IP address of the next-hop IP address.

Null (discard)

The null route consists of the destination network address or host, a corresponding network mask, and either the reject or blackhole keyword. Typically, the null route is configured as a backup route for discarding traffic if the primary route is unavailable. By default, when IP routing is enabled, a route for the 127.0.0.0/8 network is created to the null interface. Traffic to this interface is rejected (dropped.)

This route is for all traffic to the "loopback" network, with the single exception of traffic to the host address of the switch's loopback interface (127.0.0.1/32.) Figure A-3 on page 1-6 shows the default null route entry in the switch's routing table.


	NOTE: On a single routing switch you can create one null route to a given destination. Multiple null routes to the same destination are not supported.

Other sources of routes in the routing table

The IP route table can also receive routes from the following sources:

Directly connected networks: One route is created per IP interface. When you add an IP interface, the routing switch automatically creates a route for the network the interface is in.
RIP: If RIP is enabled, the routing switch can learn about routes from the advertisements other RIP routers send to the routing switch. If the RIP route has a lower administrative distance than any other routes from different sources to the same destination, the routing switch places the route in the IP route table.
OSPF: See RIP, but substitute "OSPF" for "RIP".
Default route: This is a specific static route that the routing switch uses if other routes to the destination are not available.

Static IP route parameters

When you configure a static IP route, you must specify the following parameters:

The IP address and network mask for the route's destination network or host.
The route's path, which can be one of the following:
- IP address of a next-hop router.
- "Null" interface; the routing switch drops traffic forwarded to the null interface.

The routing switch also applies default values for the route's administrative distance (page A-10.) In the case of static routes, this is the value the routing switch uses to compare a static route to routes from other route sources to the same destination before placing a route in the IP route table. The default administrative distance for static IP routes is 1, but can be configured to any value from 1 to 255.

The fixed administrative distance values ensure that the routing switch always prefers static IP routes over routes from other sources to the same destination.

Static route states follow VLAN states

IP static routes remain in the IP route table only so long as the IP interface to the next-hop router is up. If the next-hop interface goes down, the software removes the static route from the IP route table. If the next-hop interface comes up again, the software adds the route back to the route table.

This feature allows the routing switch to adjust to changes in network topology. The routing switch does not continue trying to use routes on unreachable paths, but instead uses routes only when their paths are reachable.

For example, the following command configures a static route to 207.95.7.0 (with a network mask of 255.255.255.0), using 207.95.6.157 as the next-hop router's IP address.

HP Switch(config)# ip route 207.95.7.0/24 207.95.6.157

A static IP route specifies the route's destination address and the next-hop router's IP address or routing switch interface through which the routing switch can reach the destination. (The route is added to the routing switch's IP route table.)

In the above example, routing switch "A" knows that 207.95.6.157 is reachable through port A2, and assumes that local interfaces within that subnet are on the same port. Routing switch "A" deduces that IP interface 207.95.7.188 is also on port A2. The software automatically removes a static route from the route table if the next-hop VLAN used by that route becomes unavailable. When the VLAN becomes available again, the software automatically re-adds the route to the route table.

Configuring equal cost multi-path (ECMP) routing for static IP routes

ECMP routing allows multiple entries for routes to the same destination. Each path has the same cost as the other paths, but a different next-hop router. The ip load-sharing command specifies the maximum number of equal paths that can be configured. Values range from 2 to 4.

Example of an ECMP set with the same destination but different next-hop routers

This example shows configuration of an ECMP set with two different gateways to the same destination address but through different next-hop routers. For more information, see OSPF equal-cost multipath (ECMP) for different subnets available through the same next-hop routes".

HP Switch(config)# ip route 127.10.144.21/24 10.10.10.2 metric 12 distance 10
HP Switch(config)# ip route 127.10.144.21/24 10.10.10.3 metric 12 distance 10

prev	up	next
Viewing static route information	home	Routing Information Protocol (RIP)