Elie,
This is only an idea and I don't have a time to put it all together, but...
lets assume you have scenario like this bellow:
Router Expedient - Low speed link
/
Your Standby Router (EXOS switch)
|
|
|
Your Main Router (EXOS switch)
\
Router Cogent - High speed link
You advertise your prefix for example 10.0.0.0/24 from Main router:
- dirtect to Cogent
- to Standby Router and then to Expedient
On Main Router you can have a UPM script and BGP export policy.
The UPM script will check if some route is in table and this route nexthop is via Cogent
or if the session is up and so on.
If the route does not exists, you apply iBGP_export_Stby.pol to iBGP peer out to Standby Router
and advertise prefix with community 65535:100
If all is ok, unconfigure policy iBGP_export_Stby.pol
================= iBGP_export_Stby.pol =====================
entry iBGP_peer_Main { if match all {
nlri 10.0.0.0/24;
} then {
permit;
community set 65535:100;
}}
========================================================
On Stanby Router you can have a policy that import prefix from Main router like this:
If I receive my prefix from IBGP peer Main Router with community 65535:100
then I will permit and then advertise to Expedient.
If not deny the prefix and don't advertise anything.
example
========== iBGP_import_Main.pol =============================
entry iBGP_peer_Main { if match all {
community 65535:100;
nlri 10.0.0.0/24;
} then {
permit;
}}
entry IP_BGP_deny { if {
} then {
deny;
}}
===========================================================
--
Jarek