IBGP +AS number

[sridhar ch]

Hi,

Would like to know whether we can use our AS number while configuring IBGP?

Scenario:

we have 2 sites (A&B). Both locations has dedicated MPLS links with differenet AS numbers. We have a dedicated DS3 link between site A & B. We would like to implement ibgp over the DS3 link so that if Site A MPLS goes down, traffic from site A will take the DS3 link and goes thru Site B MPLS link and vice versa.

Thanks,

Sridhar

[Ajay Raj]

Hi,

You can configure HSRP or EBGP. Please clarifiy your topology.

[blau grana]

If I understand you correctly, site A and B has same AS and they are connected with DS3 link. Both sites has also link to different ISP [different AS].

You can use your AS to peer between A and B, but it depends on your topology if you will need to use RR or iBGP full-mesh to advertise BGP routes to all iBGP peers. Also probably you will need to modify BGP parameters to prefer uplink to ISP or iBGP connection. It all depends on your requirements.

Best Regards

Please rate all helpful posts and close solved questions

[sridhar ch]

no, i want to configure iBGP between the 2 sites. Both sites has 2 dedicated MPLS links with different AS. My question is to run ibgp between two sites over DS3, can i use my own AS (not the one that we are using for eBGP) or do i need to get it from MPLS provider? i know iBGP needs to have same AS at both ends.

[blau grana]

No, it is not possible to run iBGP session between A and B site as you draw it. On one router, you can have BGP associate only with one AS.

Best way would be to use on router A and router B same AS.

ISP1

  router bgp 100

    neighbor siteA remote-as 65000

ISP2

  router bgp 200

    neighbor siteB remote-as 65000

SiteA

  router bgp 65000

    neighbor isp1 remote-as 100

    neighbor siteB remote-as 65000

SiteB

  router bgp 65000

    neighbor isp2 remote-as 200

    neighbor siteA remote-as 65000

Best Regards

Please rate all helpful posts and close solved questions