Website open Thorugh ISP-A , when multiple bandwith in single 3845 router with BGP.

Unanswered Question
Apr 6th, 2010

Dear Experts,

We are using multiple ISP Bandwidth in single 3845 router with bgp routing ( Different ASN).

We need  to open some of the website through ISP-A only.

like : www.yahoo.com , www.google.com. etc.... to open through ISP-A

because we trace out perfomance to open some of the website through ISP-A batter than ISP-B.

So how can i do this , what it the configuration in BGP or whatever i can do to achive my goal to open some of the website through ISP-A only.

thanks in ADV,

Vaib...

I have this problem too.
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Giuseppe Larosa Tue, 04/06/2010 - 10:25

Hello Vaibhav,

I see you are still fighting in this scenario.

BGP alone cannot do this kind of tasks.

You need to consider OER optimized edge routing for your scenario in order to divert traffic depending on performance criteria on the the two paths

http://www.cisco.com/en/US/docs/ios/oer/configuration/guide/12_4t/oer_12_4t_book.html

http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/Transport_diversity/PfR_Master_Controller_Redundancy.html

Hope to help

Giuseppe

csawest.dc Tue, 04/06/2010 - 22:24

Dear Giuseppe,

We are using multiple ISP bandwidth in single 3845 router.

ISP -A 45 MB and ISP-B 25 Mb.

we are  configured load sharing in bgp , and almost we achived my goal it's working fine , at a time ISP-A Bandwidth used 42 Mb that time ISP-B bandwidth used 19 mb so i think it's working fine. we are configed Weight in bgp ( ISP-A weight 50000 and ISP-B 25000). as per your guidline so thanks a lot.

Now i must need some webstie to open through ISP-A and some are ISP-B So  how can i achive this. cause i dont understand OER.

Thanks in ADV,

Vaib...

Giuseppe Larosa Wed, 04/07/2010 - 00:31

Hello Vaibhav,

I'm happy to know the eBGP setup is working. This is good news.

if you want to do this only for a few web sites you can use PBR= policy based routing.

You need to resolve with DNS the URL of interest and to create a list of ip addresses you would like to divert to the other ISP

so if web site of yahooo would be 100.200.100.22 you should divert traffic with this destination

build the list

buid an extended access-lists with lines like the following

access-list 111 permit tcp any host 100.200.200.22 eq www

this is an approximation because the web site can have multiple mirrors and also because a single web page contains content coming from different sources (think of AD banners and so on)

build a route-map

route-map WebPBR permit 10

match ip address 111

set ip next-hop ISP-ip-address

on internal interfaces you need to put

int g0/0

ip policy route-map WebPBR

as an atlernative way you could do it in BGP by using a route-map to selectively increase weight only for some prefixes

in this case you could use a prefix-list

hint: to build the route-map you need to process the list of web-sites using

sh ip bgp web-site-ip address

because you need to find out the IP prefix to which the ip address of web site belongs

so from a list of web sites ip addresses you get a list of IP prefixes.

For describing the IP prefixes you can use a prefix-list

ip prefix-list websites seq 5 permit 100.200.22.0/24

...

the route-map requires two blocks

route-map incomingISPB permit 10

match ip address prefix websites

set weight 50000

route-map incomingISPB permit 20

set weight 25000

you need to apply this inbound to neighbor ISPB

the limit is that you should review the configuration of PBR or of the route-map to keep it updated

Hope to help

Giuseppe

csawest.dc Wed, 04/07/2010 - 13:03

Deaer Giuseppe,

Thank you very much for your great reply of every time.

some little bit confution , you mean to say ( so if web site of yahooo would be 100.200.100.22 you should divert traffic with this destination) , that means 100.200.100.22 this is yahoo ip address ?? am i right ??.

access-list 111 permit tcp any host 100.200.200.22 eq www  ( here is 100.200.200.22 ,  is yahoo ip address ?? ).

Thanks in ADV,

Vaib...

Giuseppe Larosa Thu, 04/08/2010 - 06:55

Hello Vaibhav,

your understanding correct

I did an example and I've tried to be consistent with it in the post

access-list 111 permit tcp any host 100.200.200.22 eq www  ( here is  100.200.200.22 ,  is yahoo ip address ?? ).

of course the ip address is fictious

Hope to help

Giuseppe

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