From: Jing Zeng (jzeng@xxxxxxxxxx)
Date: Tue Aug 28 2001 - 17:01:39 GMT-3
First, I have a question, why you are using private address here. Or you are
doing NAT somewhere? Please clear this question.
For the traffic going out, only set the default route will not make sense
here.
Because you get the BGP routes from ISP1 and ISP2, and the router will
choose the longest match route to reach the destination, normally the router
will not use the defualt route for most of those traffic that has an
explicit route in the BGP table.
The way to solve this is set the local preference for ISP1 bigger than ISP2
( or you can set weight on cisco routers).
For the traffic coming in, the potential problem is ISP1 aggregation. So the
destination will get two routes for you, one is from ISP1 and on is from
ISP2, but the ISP1 summarize your route, so the route from ISP2 is the
longest match, them all the traffic will come to you through ISP2. This is
only the potential problem I guess, and because you are using private
address here, so not so sure.
Jing Zeng
----- Original Message -----
From: "Yves Fauser" <Yves@Fauser.de>
To: "Rick Stephens" <rstephens@wantec.com>
Cc: <ccielab@groupstudy.com>
Sent: Tuesday, August 28, 2001 6:36 AM
Subject: Re: BGP: AS-PATH PREPEND
> Hi Rick,
>
> I did not have the chance to test it in a Lab, but I don't see a <ip
> as-path access-list 1> statement in your sample config. When you are
> doing :
> ----------------------------------------------------
> route-map set-as-path 10 permit
> match as-path 1
> set as-path prepend 12345 12345 12345 12345
>
> route-map set-as-path 20 permit
> match address 2
>
> access-list 1 permit 192.168.1.0 0.0.0.255
> access-list 2 permit 0.0.0.0 255.255.255.255
> ----------------------------------------------------
>
> I think you wanted to do :
> -----------------------------------------------------
> route-map set-as-path 10 permit
> match ip address 1
> set as-path prepend 12345 12345 12345 12345
>
> route-map set-as-path 20 permit
>
> access-list 1 permit 192.168.1.0
> -----------------------------------------------------
> This should prepend the as-path <12345 12345 12345 12345> to the
> 192.168.1.0 prefix
>
> Or you could do :
> -----------------------------------------------------
> ip as-path access-list 1 permit ^$
>
> route-map set-as-path 10 permit
> match as-path 1
> set as-path prepend 12345 12345 12345 12345
>
> route-map set-as-path 20 permit
> ------------------------------------------------------
> This should prepend the as-path <12345 12345 12345 12345> to all
> prefixes that are localy originated by your AS.
>
> hope this helps,
>
> Yves
>
>
> Rick Stephens wrote:
>
> > Group,
> > I have a T1 connection going to one ISP (AS 111), and a second 384K
> > connection going to a different ISP (AS 222). We would like to use the
> > second connection for backup only. That is, no load sharing rather only
to
> > be used if the T1 goes down.
> > The T1 is out Serial 0/0.1. The backup connection is out a Wireless
> > Ethernet. My thought was that simple static routes with adminstrative
> > distance would prevent the backup line from being used when going out.
But
> > the BGP configuration is giving me a little trouble. I thought I could
> > prepend the path to the backup connection to make the T1 path to the 1st
ISP
> > the best route. But, whenever I set this configuration the incoming
traffic
> > comes in through the 2nd ISP. Where am I going wrong? What is the best
way?
> > Thank you in advance.
> >
> > router bgp 12345
> > network 192.168.1.0 mask 255.255.255.0
> > ! Primary Neighbor (T1 Connection)
> > neighbor 172.16.1.1 remote-as 111
> > ! Backup Wireless Neighbor (384K Connection)
> > neighbor 172.16.10.1 remote-as 222
> > neighbor 172.16.10.1 route-map set-as-path out
> >
> > ip route 0.0.0.0 0.0.0.0 Serial0/0.1
> > ip route 0.0.0.0 0.0.0.0 172.16.10.1 100
> >
> > route-map set-as-path 10 permit
> > match as-path 1
> > set as-path prepend 12345 12345 12345 12345
> >
> > route-map set-as-path 20 permit
> > match address 2
> >
> > access-list 1 permit 192.168.1.0 0.0.0.255
> > access-list 2 permit 0.0.0.0 255.255.255.255
> > **Please read:http://www.groupstudy.com/list/posting.html
> **Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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