ROUTING IN BGP

[amit_kulshrestha_2]

Dear Friends,

      I have came to you with a very strange request from one our customer , Our Customer is having big enterprise network with many remote location, on some Remote location there are 2 ISP and some there is only 1 ISP , they are having mix routing in their envirnoment , with some ISP they are having static , with some they are having OSFP and with some they are having BGP(there are all total 6 ISP), now out of 6 ISP two ISP naming ISP-A and ISP-B, with this ISP-A and ISP-B , there about almost 25 or 30 remote location are connected and very thing is work fine , but for customer ISP-A is more reliable then ISP-B  which it is actually, with ISP-A BGP is runing and ISP-B OSPF is running , link failover is happening . Customer want many thing , like wise to say , in remote site where there are 2 ISP ,especailly where ISP-A & ISP-B are there , they want both the link to be utilizied , i-e if there are 6 apps 3 apps should work from ISP-A and 3 should work from ISP-B , which we have achieved through giving static routes , and PBR in Central site , also if ISP-A goes down , traffic shift to ISP-B , but static route given for ISP-A does not shift automatically.They want that those static routes given should shift automatically , which are given forcefully to use either primarily or secondary link.

(In case , I am uble to make you understand , than below is copy paste of mail )

For all the location ,application wise redundancy for link load sharing through PBR and static route in all remote location has been done .In case of any link goes down traffic automatic shifted on other available link except static route that we moved towards forcefully  on other  link We already published 192.168.0.0/16 subnet in all the ISPs .

For example we have one location having MPLS link of ISP-A primary  and ISP-B link is secondary 

In case of primary link goes down all the traffic 192.168.0.0/16 traffic shifted on secondary link automatic except static route and for static route we have to remove this route from  router and make changes in PBR

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Kindly help as soon as possible for all of you.

Regards

Amit Kulshrestha

[Lei Tian]

Hi Amit,

Think realiable static routing might help.

http://www.cisco.com/en/US/docs/ios/dial/configuration/guide/dia_rel_stc_rtg_bckup.html

They can also consider PfR, which essentially will use PBR to shift the traffic when 2 different routing protocol are used. 

http://www.cisco.com/en/US/products/ps8787/products_ios_protocol_option_home.html

HTH,

Lei Tian

[Joseph Nelson]

Amit,

Lei Tians suggestion is correct. I've used static routes with tracking extensively ( actually it's is the only way I feel safe using a static ):

!!! Track interface connected to ISP-A
track 1 interface line-protocol
!!! Track interface connected to ISP-B
track 2 interface line-protocol
!!! Equal cost statics through both ISPs for load balancing
ip route 0.0.0.0  track 1
ip route 0.0.0.0  track 2

It should be noted that tracking the line-protocol on an interface does not detect soft failures like misconfigs on the ISPs BGP. So another question would be what does your client interpret as "unreliable" is it links going down or is it path performance ( e.g. latency, loss, etc ) accross the link. If its path performance, than PfR is definitely something you should look into.

You can also track on IP SLA which gives you about the same failover ability as PfR without the complexity.

HTH

[amit_kulshrestha_2]

Thanks Josph and Lei, for your help, let me try , will revert you back with results.