Configuring BGP4

Defining IP Prefix Lists

An IP prefix list specifies a list of networks. When you apply an IP prefix list to a neighbor, the routing switch sends or receives only a route whose destination is in the IP prefix list. You can configure up to 100 prefix lists. The software interprets the prefix lists in order, beginning with the lowest sequence number.

USING THE CLI

To configure an IP prefix list and apply it to a neighbor, enter commands such as the following:

HP9300(config)# ip prefix-list Routesfor20 permit 20.20.0.0/24 HP9300(config-bgp-router)# neighbor 10.10.10.1 prefix-list Routesfor20 out

These commands configure an IP prefix list named Routesfor20, which permits routes to network 20.20.0.0/24. The neighbor command configures the routing switch to use IP prefix list Routesfor20 to determine which routes to send to neighbor 10.10.10.1. The routing switch sends routes that go to 20.20.x.x to neighbor 10.10.10.1 because the IP prefix list explicitly permits these routes to be sent to the neighbor.

Syntax: ip prefix-list <name> [seq <seq-value>] [description <string>] deny permit <network-addr>/<mask-bits> [ge <ge-value>] [le <le-value>]

The <name> parameter specifies the prefix list name. You use this name when applying the prefix list to a neighbor.

The description <string> parameter is a text string describing the prefix list.

The seq <seq-value> parameter is optional and specifies the IP prefix list’s sequence number. You can configure up to 100 prefix list entries. If you do not specify a sequence number, the software numbers them in increments of 5, beginning with prefix list entry 5. The software interprets the prefix list entries in numerical order, beginning with the lowest sequence number.

The deny permit parameter specifies the action the software takes if a neighbor’s route is in this prefix list.

The prefix-list matches only on this network unless you use the ge <ge-value> or le <le-value> parameters. (See below.)

The <network-addr>/<mask-bits> parameter specifies the network number and the number of bits in the network mask.

You can specify a range of prefix length for prefixes that are more specific than <network-addr>/<mask-bits>.

•If you specify only ge <ge-value>, then the mask-length range is from <ge-value> to 32.

•If you specify only le <le-value>, then the mask-length range is from length to <le-value>. The <ge-value> or <le-value> you specify must meet the following condition:

length < ge-value <= le-value <= 32

If you do not specify ge <ge-value> or le <le-value>, the prefix list matches only on the exact network prefix you specify with the <network-addr>/<mask-bits> parameter.

For the syntax of the neighbor command shown in the example above, see “Adding BGP4 Neighbors” on page 10-14.

USING THE WEB MANAGEMENT INTERFACE

To configure an IP Prefix List, use the following procedure:

1.Log on to the device using a valid user name and password for read-write access. The System configuration panel is displayed.

2.Click on the plus sign next to Configure in the tree view to display the list of configuration options.

3.Click on the plus sign next to IP to display the list of IP configuration options.

4.Select the Prefix List link.

•If the device does not have any prefix list ACLs, the IP Prefix List panel is displayed, as shown in the following example.

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