(no subject)

hello !

Im stuck in this BGP multihoming Issue , need your help

I have attached the diagram ...

The Organization has been alloted a pool lets say 192.168.128.0/22 from the
RIR like APNIC
and also it has a public AS.

It peers with two ISPs . ISP A and ISP B.

The Traffic flow must be such as ... all incoming traffic must be preferred
through ISP A
except the two pools 192.168.130.0/24 and 192.168.131.0/24 which must be
preferred
through ISP B.

For
this I have advertised 192.168.128.0 /22 to ISP A and the two /24 pools
to ISP B along with the /22 pool with AS Path Prepended to it.

The Incoming Traffic flow is according to the requirements ..

The problem is with the outgoing traffic.

All outgoing traffic must exit through ISP A except the /24 pools which must
use ISP B.
This prevents Asymmetric routing.

Both providers send the default route. I have configured ospf between the
Routers and the
switch,
and used the default-information originate command on the routers.
Router connected to ISP A Advertises the default with metric 20 and
Router connected to ISP B
advertises the default with metric of 30 to the L3 Switch

As
the traffic from / 24 pools must exit ISP B , i configured a Routing
policy on switch to send traffic sourcing from these pools to ISP B
which works ..

But the Problem comes when BGP connection to ISP
B fails. The switch through policy routing sends traffic from /24 pools
to Router connected to ISP B which now doesnot have the BGP Default
Route but it has a default route from router connected to ISP A through
OSPF. The switch and routers are in the same broadcast network.

What
I see is the problem is that the Router connected to ISP B is not
sending the same traffic back to same interface because the default
from OSPF is on the same interface where the traffic is coming from the
/ 24 pools ... is it the right behaviour ?

Do you have any solution to the outgoing traffic requirement using other
techniques ?

Please Help

Regards
Zeeshan
Received on Tue Mar 31 2009 - 23:53:26 ART