Hello Jeffrey

iBGP is running between R1 and R2. The route-map is only for advertising
output traffic, with as-prepend, for some routes and not others. Don't
care about it. When "sh ip bgp ISPX advertised" on each router, ALL
routes are advertised on both routers. This configuration work well.


So if ISP1 trunk fail, Traffic is re-routed via iBGP to R2 and then to
ISP2. This work well on my network. The only problem now is incoming
traffic as satellite bandwidth is not cheap. 


Jacques VUVANT
Network OPT New-Caledonia
Phone	: +687-267541
Fax	: +687-278444
Mob	: +687-773121
Mail	: Jacques.vuvant@... 


-----Message d'origine-----
De : Jeffrey Belles [mailto:jaffa@...Envoyé : vendredi 18 juillet 2003 17:44
À : isp-bgp@isp-bgp.com
Objet : [isp-bgp] Re: Advertising in BGP

Hi Jacques,

From the snippet of config you pasted below:
I see you are not advertising all of your 6 (now 7) prefixes to _both_
upstreams, just 3 to ISP1 and 3 to ISP2.
This will work, yes, but has not really added BGP-functionality. It has
the
same effect as statically routed blocks.
What if the trunk to ISP-1 fails?
The 3 prefixes you announce to them are not announced to ISP-2 and will
disappear from the global routing-table.
You should try and announce all of your blocks to all upstreams and then
let
AS_PATH (or any other attribute you see fit) do the balancing:

=========
On router 1:
=========
 neighbor Loopback0 remote-as ISP1
 neighbor Loopback0 route-map ISP1-IN in
 neighbor Loopback0 route-map ISP1-OUT out
!
ip as-path access-list 2 permit ^$
!
ip prefix-list prepend seq 10 permit network1/24 le 32
ip prefix-list prepend seq 15 permit network2/24 le 32
ip prefix-list prepend seq 20 permit network3/24 le 32
!
ip prefix-list no-prepend seq 10 permit network4/24 le 32
ip prefix-list no-prepend seq 15 permit network5/24 le 32
ip prefix-list no-prepend seq 20 permit network6/24 le 32
!
route-map ISP1-OUT permit 20
 match ip address prefix-list prepend
 match as-path 2
 set as-path prepend MyAS MyAS
!
route-map ISP1-OUT permit 30
match ip address prefix-list no-prepend
match as-path 2

=========
On router2:
=========
 neighbor Loopback0 remote-as ISP2
 neighbor Loopback0 route-map ISP2-IN in
 neighbor Loopback0 route-map ISP2-OUT out
!
ip as-path access-list 2 permit ^$
!
ip prefix-list prepend seq 10 permit network4/24 le 32
ip prefix-list prepend seq 15 permit network5/24 le 32
ip prefix-list prepend seq 20 permit network6/24 le 32
!
ip prefix-list no-prepend seq 10 permit network1/24 le 32
ip prefix-list no-prepend seq 15 permit network2/24 le 32
ip prefix-list no-prepend seq 20 permit network3/24 le 32

!
route-map ISP2-OUT permit 20
 match ip address prefix-list prepend
 match as-path 2
 set as-path prepend MyAS MyAS
!
route-map ISP2-OUT permit 30
match address prefix-list no-prepend
match as-path 2

As for the 7-nd block: route it however you want..

Cheers,
Jeffrey Belles



----- Original Message -----
From: "Jacques VUVANT" <jacques.vuvant@...>
To: <isp-bgp@isp-bgp.com>
Sent: Friday, July 18, 2003 3:40 AM
Subject: [isp-bgp] Advertising in BGP


> Hello all
>
> I have a network constituted with 2 routers (R1 and R2)connected on
> iBGP, and each router is connected in eBGP to ISPs (ISP1 and ISP2).
I'm
> trying to manage incoming traffic of routes advertised by my AS with
> prefix and route-map with as-prepend as following and it work well,
see
> configuration:
>
> On R1
> =====
> router bgp MyAS
> .....
>  neighbor Loopback0 remote-as ISP1
>  neighbor Loopback0 route-map ISP1-IN in
>  neighbor Loopback0 route-map ISP1-OUT out
> !
> ip as-path access-list 2 permit ^$
> !
> ip prefix-list TO-R2 seq 10 permit network1/24 le 32
> ip prefix-list TO-R2 seq 15 permit network2/24 le 32
> ip prefix-list TO-R2 seq 20 permit network3/24 le 32
> !
> route-map ISP1-OUT permit 20
>  match ip address prefix-list TO-R2
>  match as-path 2
>  set as-path prepend MyAS MyAS
> !
> route-map ISP1-OUT permit 30
>  match as-path 2
>
>
> On R2
> ========
> router bgp MyAS
> .....
>  neighbor Loopback0 remote-as ISP2
>  neighbor Loopback0 route-map ISP2-IN in
>  neighbor Loopback0 route-map ISP2-OUT out
> !
> ip as-path access-list 2 permit ^$
> !
> ip prefix-list TO-R1 seq 10 permit network4/24 le 32
> ip prefix-list TO-R1 seq 15 permit network5/24 le 32
> ip prefix-list TO-R1 seq 20 permit network6/24 le 32
> !
> route-map ISP2-OUT permit 20
>  match ip address prefix-list TO-R1
>  match as-path 2
>  set as-path prepend MyAS MyAS
> !
> route-map ISP2-OUT permit 30
>  match as-path 2
>
> My question is if I add route on both Prefix-list, for example:
>
> On R1:
> ======
> ip prefix-list TO-R2 seq 10 permit network1/24 le 32
> ip prefix-list TO-R2 seq 15 permit network2/24 le 32
> ip prefix-list TO-R2 seq 20 permit network3/24 le 32
>
> On R2:
> ======
> ip prefix-list TO-R1 seq 10 permit network4/24 le 32
> ip prefix-list TO-R1 seq 15 permit network5/24 le 32
> ip prefix-list TO-R1 seq 20 permit network6/24 le 32
> ip prefix-list TO-R2 seq 20 permit network3/24 le 32
>
> What should happen on advertising ?
>
> Thanks for any answer
>
>
> Jacques VUVANT
> Network OPT New-Caledonia
> Phone : +687-267541
> Fax : +687-278444
> Mob : +687-773121
> Mail : Jacques.vuvant@...
>
>
> -----Message d'origine-----
> De : Carl-Henrik Landgren [mailto:landgren@...
> Envoyé : mercredi 16 juillet 2003 23:19
> À : isp-bgp@isp-bgp.com
> Cc : isp-bgp@isp-bgp.com
> Objet : [isp-bgp] RE: Sample BGP Config
>
> Depending on what link you want the traffic to take, it's pretty
> simple....
>
> Just make the link you don't want the outbound traffic to pass with a
> longer AS-PATH, just add your own AS to the AS-SEQUENCE several times
to
> make it long enough.
>
> Or, you can filter with LOCAL-PREF for the prefixes you want the
> outbound-traffic to exit your AS.
>
> The rest i assume you know how to configure yourself.
>
> /Carl
>
>
>
> ------- Ursprungligt brev -------
> Från: chris@...
> Datum: Tue, 15 Jul 2003 14:58:48 -0700
>
> Michael,
>
> Thanks for the response.  The example I read was "Load Sharing when
> Multihomed to Two ISPs via Multiple Local Routers"
>
> The outbound traffic policy in this example limits traffic to one of
the
> two providers unless there is a failure.
>
> The outbound traffic policy is as follows:
> Traffic destined to AS 300 goes via the R1 - ISP(A) link.
> Traffic destined to AS 400 goes via the R2 - ISP(B) link.
> All other traffic should prefer default route 0.0.0.0 via the R1 -
> ISP(A) link.
> If the R1 - ISP(A) link fails, all traffic should go via the R2 -
ISP(B)
> link.
>
> I'd like to have outbound traffic take the shortest path if both ISP's
> are up and fail over to the other ISP if one ISP link fails.
>
>
> Christopher J. Wolff, VP CIO
> Broadband Laboratories, Inc.
> http://www.bblabs.com
>
> -----Original Message-----
> From: Michael Weinstock [mailto:MWeinstock@...> Sent: Tuesday, July 15, 2003 2:50 PM
> To: isp-bgp@isp-bgp.com
> Subject: [isp-bgp] RE: Sample BGP Config
>
> Hello,
>
> You didnt like it? Perhaps specify what you didnt like... As the
answer
> will be based on Cisco's docs.
>
> -----Original Message-----
> From: Christopher J. Wolff [mailto:chris@...> Sent: Wednesday, 16 July 2003 9:47 a.m.
> To: isp-bgp@isp-bgp.com
> Subject: [isp-bgp] Sample BGP Config
>
>
> Hello,
>
> I'm looking for a couple of sample cisco configs that illustrate two
> multihomed routers connected by an IGP session.  For example;
>
> Router 1----------Isp 1
> |
> |
> IGP
> |
> |
> Router 2----------Isp 2
>
> I read the Cisco scenarios for multihomed networks documents but I
> didn't like what I read.  Thank you in advance.
>
> C.J. Wolff, VP CIO
> Broadband Laboratories, Inc.
> http://www.bblabs.com
>
>
>
>
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Replies

[isp-bgp] Re: Advertising in BGP, Jeffrey Belles