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8-24 neighbor { ip-address peer- group - name } remove-private-asSyntax Description:
Purpose: To remove private autonomous systems in updates to the neighbor or peer group. Private AS numbers are in the range 64512 to 65535. Private AS numbers should not be advertised to the Internet. The following conditions apply when using this command:
Cisco IOS Software Release: 12.0 Configuration Example: Removing a Private AS Number from Updates to Neighbors or Peer GroupsIn Figure 8-24, an ISP is connected to a customer who is using a private AS number. The ISP is connected to another ISP for Internet connectivity. The ISP in AS 1 needs to remove the private AS number before advertising routes to the ISP in AS 2. Figure 8-24. Private AS Numbers Should Be Suppressed If Routes Are Advertised to the Internet
Router A router bgp 65530 network 172.16.0.0 mask 255.255.255.0 network 172.16.1.0 mask 255.255.255.0 network 172.16.2.0 mask 255.255.255.0 network 172.16.3.0 mask 255.255.255.0 neighbor 10.1.1.2 remote-as 1 __________________________________________________________________________ Router B router bgp 1 neighbor 10.1.1.1 remote-as 65530 neighbor 10.1.2.2 remote-as 2 neighbor 10.1.2.2 remove-private-as __________________________________________________________________________ Router C router bgp 2 neighbor 10.1.2.1 remote-as 1 VerificationBefore using the command neighbor 10.1.2.2 remove-private-as, check the BGP tables on Routers B and C to view the private AS number in the AS path: rtrB# show ip bgp BGP table version is 21, local router ID is 172.16.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 172.16.0.0/24 10.1.1.1 0 0 65530 i *> 172.16.1.0/24 10.1.1.1 0 0 65530 i *> 172.16.2.0/24 10.1.1.1 0 0 65530 i *> 172.16.3.0/24 10.1.1.1 0 0 65530 i __________________________________________________________________________ rtrC# show ip bgp BGP table version is 5, local router ID is 156.26.32.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 172.16.0.0/24 10.1.2.1 0 1 65530 i *> 172.16.1.0/24 10.1.2.1 0 1 65530 i *> 172.16.2.0/24 10.1.2.1 0 1 65530 i *> 172.16.3.0/24 10.1.2.1 0 1 65530 i Now add the command neighbor 10.1.2.2 remove-private-as on Router B and recheck the BGP table on Router C: rtrC# show ip bgp BGP table version is 5, local router ID is 156.26.32.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 172.16.0.0/24 10.1.2.1 0 1 i *> 172.16.1.0/24 10.1.2.1 0 1 i *> 172.16.2.0/24 10.1.2.1 0 1 i *> 172.16.3.0/24 10.1.2.1 0 1 i As you can see, the private AS number (65530) has been removed. Troubleshooting
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