Home BGP Knowledge Base How to hide private ASN from ISP

We know how to change peer ASN without changing BGP processor ID which might be private ASN. That is local-as commands is the one to replace ASN for outside of world. However, your BGP peer keep on sending private ASN or current BGP processor ID. Here is the magic command to fix it.

"neighbor x.x.x.x local-as yyy no-prepend replace-as"

From below example, we will use ASN 100 on R1 to peer with R5. After configured R1, we got following output.

 BGP_local_AS.png

 

R1(config-router)# neighbor 10.10.15.5 local-as 100

R5# sh ip bgp
BGP table version is 69, local router ID is 200.5.5.5
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.0.0.0         10.10.15.1               0             0 100 65500 i
*> 10.10.12.0/24    10.10.15.1               0             0 100 65500 i
*> 10.10.13.0/24    10.10.15.1               0             0 100 65500 i
r> 10.10.15.0/24    10.10.15.1               0             0 100 65500 i
*> 10.10.26.0/24    10.10.15.1                             0 100 65500 i
*> 30.30.30.0/24    10.10.15.1                             0 100 65500 i
*> 100.100.100.0/24 10.10.15.1               0             0 100 65500 i
R5#


 

R1(config-router)# neighbor 10.10.15.5 local-as 100 no-prepend replace-as

R5# sh ip bgp
BGP table version is 84, local router ID is 200.5.5.5
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 10.0.0.0         10.10.15.1               0             0 100 i
*> 10.10.12.0/24    10.10.15.1               0             0 100 i
*> 10.10.13.0/24    10.10.15.1               0             0 100 i
r> 10.10.15.0/24    10.10.15.1               0             0 100 i
*> 10.10.26.0/24    10.10.15.1                             0 100 i
*> 30.30.30.0/24    10.10.15.1                             0 100 i
*> 100.100.100.0/24 10.10.15.1               0             0 100 i
R5#


 

Last Updated (Monday, 10 May 2010 15:11)

 
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