OK. I did some basic testing. Here is what I found: if you use the neighbor a.b.c.d local-as xxxx form of the command, then your neighbor sees you as AS xxxx, no matter what you have configured as your "real" AS.
------------ router bgp 5555 neighbor a.b.c.d remote-as 1000 neighbor a.b.c.d local-AS xxxx router bgp 1000 neighbor w.x.w.z remote-as xxxx ----------- your neighbor has to use the neighbor a.b.c.d remote-as xxxx, matching what you say is your local-as all routes sent to that neighbor have the "xxxx" as the most recent AS in the AS-Path. Doing it this way would accomplish what you are asking. The intent of the local-AS command apears to relate to BGP confederations and the way they behave. The alrternative method, as shown in the configuration guides on CCO, appears to be a means of modifying inbound routes to achieve the optional community status of local-AS. that is, these routes will be retained only in the local ( iBGP / confederation ) BGP table. and will not be advertised to an esternal BGP peer. Not being a BGP sophisticate, I may well be misunderstanding some of this. I invite those with better understanding to clarify. I certainly am hard pressed to see any value to this, but then I can fill a small library with what I don't know about the subtleties of BGP. HTH Chuck ""news"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi > > what I am trying to achieve is as follow > > AS 100 is connected to AS 200. > AS 200 is connected to AS 300 > > AS 100 has route from AS 300. So the AS-PATH List is: 200, 300, i > The task is: AS 100 should see all the route from AS 300 as if they came > from AS 100 directly the path will look like 200, i > > Faisal > > > ""Chuck Larrieu"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > interesting question. a seach among the command references and > > configuration guides on CCO yields nothing under 12.1, but under 12.2 > states > > this command was introduced in 12.0(4.4)S and that in 12.0(5)T > > the address family configuration mode was added. > > > > I copied this stuff out of CCO, but it is not making sense to me at the > > moment. I can find no reference to the command and function in Parkhurst, > > which carries a 2001 copyright but no telling when the contents were > locked > > down for publishing. > > > > In re-reading this thread and the documentation below, I'm still a bit > > unclear as to what is being accomplished here. Telling a neighbor you are > AS > > X when you are really AS Y ?? > > > > I'm working on some BGP scenarios now, so I'll try to add this to the list > > and report back. > > > > Chuck > > > > ---------- > > stuff from CCO: > > > > > > The next example shows how the route map named set-community is applied to > > the outbound updates to neighbor 171.69.232.50 and the local-as community > > attribute is used to filter the routes. The routes that pass access list 1 > > have the special community attribute value local-as. The remaining routes > > are advertised normally. This special community value automatically > prevents > > the advertisement of those routes by the BGP speakers outside autonomous > > system 200. > > > > router bgp 65000 > > network 1.0.0.0 route-map set-community > > bgp confederation identifier 200 > > bgp confederation peers 65001 > > neighbor 171.69.232.50 remote-as 100 > > neighbor 171.69.233.2 remote-as 65001 > > ! > > route-map set-community permit 10 > > set community local-as > > > > > > neighbor local-as > > To allow customization of the autonomous system number for external Border > > Gateway Protocol (eBGP) peer groupings, use the neighbor local-as command > in > > address family or router configuration mode. To disable this function, use > > the no form of this command. > > > > Command History Release Modification > > 12.0(4.4)S > > This command was introduced. > > > > 12.0(5)T > > Address family configuration mode was added. > > > > > > > > > > Usage Guidelines > > > > Each BGP peer or peer group can be made to have a local autonomous system > > value for the purpose of peering. In the case of peer groups, the local > > autonomous system value is valid for all peers in the peer group. > > > > This feature cannot be customized for individual peers in a peer group. > > > > If this command is configured, you cannot use the local BGP autonomous > > system number or the autonomous system number of the remote peer. > > > > This command is valid only if the peer is a true eBGP peer. This feature > > does not work for two peers in different subautonomous systems in a > > confederation. > > > > Examples > > > > The following address family configuration example shows the customization > > of neighbor 172.20.1.1 configured to have an autonomous system number of > 300 > > for the purpose of peering: > > > > router bgp 109 > > address-family ipv4 multicast > > network 172.20.0.0 > > neighbor 172.20.1.1 local-as 300 > > > > The following router configuration example shows the customization of > > neighbor 172.20.1.1 configured to have autonomous system number of 300 for > > the purpose of peering: > > > > router bgp 109 > > network 172.20.0.0 > > neighbor 172.20.1.1 local-as 300 > > > > > > end of stuff from CCO > > ----------------- > > > > > > ""adam lee"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > What version of IOS is that command in? I am using 12.0(9) and it's not > in > > > there. > > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > > news > > > Sent: Saturday, November 03, 2001 12:23 PM > > > To: [EMAIL PROTECTED] > > > Subject: Re: BGP question [7:25130] > > > > > > > > > I think I got the correct answer > > > > > > On R3, use neighbor ip address local-as AS# > > > > > > Faisal > > > > > > ""Wojtek Zlobicki"" wrote in message > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > Oops, > > > > > > > > I misunderstood the question... what is the correct answer ? > > > > > > > > > How is this command going to change the AS path list. The require > > task > > > > was > > > > > that R4 should see the loopback is from AS 200 not AS 100 (which is > > the > > > > > originator). > > > > > > > > > > Faisal > > > > > > > > > > > > > > > ""Wojtek Zlobicki"" wrote in message > > > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > > > ""news"" wrote in message > > > > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > > > > Hello, > > > > > > > > > > > > > > greetings... > > > > > > > While practicing for CCIE lab, I encounter a question that is > > > > something > > > > > > like > > > > > > > this > > > > > > > > > > > > > > Topology: > > > > > > > R1 ---- R3 ----- R4 > > > > > > > > > > > > > > R1 is on AS 100 > > > > > > > R3 is on AS 200 > > > > > > > R4 is on AS 500 > > > > > > > > > > > > > > There is a loopback address on R1 Loopback0 200.200.200.1/24. I > > am > > > > > > suppose > > > > > > > to advertise this through BGP. Now, in normal case, R4 should > see > > > > this > > > > > > > network coming from AS 200 and then AS 500 > > > > > > > > > > > > > > My task is to configure R3 with one statement so that R4 see > this > > > > > loopback > > > > > > > coming from AS 200 instead of AS 500? > > > > > > > Any idea how this is done? > > > > > > > > > > > > neighbor R3_LOOPBACK next-hop-self > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks in advance. I appreciate your help. > > > > > > > > > > > > > > Faisal Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=25236&t=25130 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
