Cisco IE-5000 User Manual

859
Configuring IP Unicast Routing
Configuring BGP
BEFORE YOU BEGIN
Enable BGP routing as described in the Enabling BGP Routing, page 850.
DETAILED STEPS
EXAMPLE
In the following example, an autonomous system path access list (number 500) is defined to configure the router to not
advertise any path through or from autonomous system 65535 to the 10.20.2.2 neighbor:
Switch(config)# ip as-path access-list 500 deny _65535_
Switch(config)# ip as-path access-list 500 deny ^65535$
Switch(config)# router bgp 50000
Switch(config-router)# neighbor 192.168.1.1 remote-as 65535
Switch(config-router)# neighbor 10.20.2.2 remote-as 40000
Switch(config-router)# neighbor 10.20.2.2 filter-list 500 out
Switch(config-router)# end
Configuring Prefix Lists for BGP Filtering
You can use prefix lists as an alternative to access lists in many BGP route filtering commands, including the neighbor
distribute-list router configuration command. Filtering by a prefix list involves matching the prefixes of routes with those
listed in the prefix list, as when matching access lists. When there is a match, the route is used. Whether a prefix is
permitted or denied is based upon these rules:
 An empty prefix list permits all prefixes.
 An implicit deny is assumed if a given prefix does not match any entries in a prefix list.
 When multiple entries of a prefix list match a given prefix, the sequence number of a prefix list entry identifies the
entry with the lowest sequence number.
By default, sequence numbers are generated automatically and incremented in units of five. If you disable the automatic
generation of sequence numbers, you must specify the sequence number for each entry. You can specify sequence
values in any increment. If you specify increments of one, you cannot insert additional entries into the list; if you choose
very large increments, you might run out of values.
You do not need to specify a sequence number when removing a configuration entry. Show commands include the
sequence numbers in their output.
Command Purpose
1. configure terminal Enter global configuration mode.
2. ip as-path access-list
access-list-number {permit | deny}
as-regular-expressions
Define a BGP-related access list.
3. router bgp autonomous-system Enter BGP router configuration mode.
4. neighbor {ip-address | peer-group
name} filter-list {access-list-number |
name} {in | out | weight weight}
Establish a BGP filter based on an access list.
5. end Return to privileged EXEC mode.
6. show ip bgp neighbors [paths
regular-expression]
Verify the configuration.
7. copy running-config startup-config (Optional) Save your entries in the configuration file.

Cisco IE-5000 Specifications

General

Brand	Cisco
Model	IE-5000
Category	Switch
Language	English