BGP Multi Homing

[alshamlan]

Dear,

I am an ISP that have multi homing with two upsteam provider. I have BGP configuration with both ISP.

ISP - A : send me full routing BGP table and it worked with me fine when the ISP-B disconnected ( for outgoing and incoming traffic)

ISP-B : send me the defualt route 0.0.0.0 only,

when both are connected the outgoing always from ISP-A and incoming from ISP-B. however, whenever i disconnect ISP-A I cannot receive or send any traffic through ISP-B .

apprciate your help and cooperation.

regards

MHS

[germain85]

Hi Alshamlan,

Follow is one link with one scenario like your's:

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a008009456d.shtml#diag

Regrds

Germain

[alshamlan]

Hi Azher,

after I did the static route to google IP , I couldnt even ping the google IP after I did the static route.

show ip cef exact-route output mentioned above.

Thnx

[Azhar Munawar]

Dear MHS,

Kindly run traceroute command for google ip and find where its stuck.

Regards,

Azhar

[alshamlan]

hi azhur,

It didnt get response from any next hops. stuck at the begning.

regards

MHS

[Azhar Munawar]

Dear MHS,

Do one more thing use tracert with source interface your loopback and interface ip which you use for BGP neighbor

for example:

tracert google.com source gig0/0  (isb b interface)

or

tracert google.com source gig0/1  (your inside interface which you use for bgp neighbor)

Also check your ACL.

Regards,

Azhar

[jens.petter.johansen]

alshamlan wrote:
ISP-A sending full BGP routing to me, and I am sending the full subnet with half subnet.
ISP-B sending to me the defualt route and I am sending the full subnet and the other half of the subnet.

Why are you splitting your subnett out to your providers? And is there any special reason you need the full table from your isp A?. If not, I would recomend that you do a simple configuration (or at least start with) where you only allow default via BGP from both ISP and where you are sending them both the exact same local prefix. You need to take care so you not become a transit AS with between your ISP A and ISP B

Can you attach a show ip bgp neigh advertice-routes and shop ip bgp neighbor received-routes from both ISP neighbor's. Also, shut your ISP-A and do the same. (if this is something that you can do?)

Jens

[Luis Mercado]

Hi, your trace from inside the network should drop at least at routerb when Ispa is shut down. Make sure your ispb is not applying a no advertise or no export community to the default they are advertising.

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