Allied Telesis VERSION 5.4.3-2.6, BGP4 manual How to apply BGP filtering for private AS numbers

BGP and BGP4+ Introduction

How to apply BGP filtering for private AS numbers

Apply BGP filtering for private AS numbers using the neighbor <neighborid> remove-private-AScommand. See this example from Router Configuration mode:

awplus# configure terminal

awplus(config)# router bgp 5

awplus(config-router)#neighbor 192.168.0.2 remove-private-AS

If the non-default AS path attribute command is applied to the Router 2 BGP configuration then the private AS is correctly filtered. See the sample console command entries below:

Router 2#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router 2(config)#router bgp 5

Router 2(config-router)#neighbor 192.168.0.2 remove-private-AS

Router 2(config-router)#exit

Router 2(config)#exit

Router 2#clear ip bgp *

The show ip bgp command output on ISP Router 1 shows that the update for the network 10.0.0.0/24 received from Router 2 (192.68.0.1) has an AS path attribute 5. This is the AS number of Router 2, without private AS path 65000.

In the ISP router BGP prefix table below, the only AS path attribute for the 10.0.0.0/24 network is '5', and the AS 65000 has been correctly filtered out from the update sent by Router 2 received into ISP Router 1. This is displayed in the show ip bgp output below:

Router 1#show running-config router bgp

!

router bgp 1

neighbor 192.168.0.1 remote-as 5 neighbor 192.168.0.2 remove-private-as

!

Router 1#show ip bgp

BGP table version is 1041, local router ID is 192.168.0.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal l - labeled, S Stale

Origin codes: i - IGP, e		- EGP, ? - incomplete
Network	Next	Hop	Metric LocPrf Weight Path
*> 10.0.0.0/24	192.168.0.1		0	0 5	i
*> 172.30.0.0	192.168.0.1		0	0 5	i
*> 192.168.0.0	192.168.0.1		0	0 5	i

	Software Reference Supplement for SwitchBlade® x8112, x908, x900 and x610 Series Switches
C613-50032-01 REV D	AlliedWare PlusTM Operating System - Software Version 5.4.3-2.6	1.41