[c-nsp] BFD w/ static routes

[Pekka Savola]

Hi,

On Thu, 4 Aug 2005, Rodney Dunn wrote:
> CSCsb48249
> Externally found enhancement defect: New (N)
> Request for BFD integration with object tracking
>
> It's on the roadmap from what I've been told.

Thanks!

> Could you explain the exact topology you want this
> for?

                I primary link
--- [PE rtr] ----- customer1 rtr
        |       I         |
        |       I         |
--- [PE rtr2] ---- customer1 rtr2
                I standby, backup link

The customer has two links to the ISP.  One is never used except for 
backup purposs (control messages to ensure liveness is OK, but no 
load-balancing is needed in our case, though that's possible as well).

The ISPs PE routers run iBGP or an IGP between each other.  The 
customer is routed with static routing.  When the primary link goes 
down, due to media converters or whatever, the PE and customer router 
may still think the link is up.  The customer's prefix is still routed 
towards the failed link (and the same for customer's default route 
pointing to the ISP) and traffic is blackholed.

This problem is typically solved by running BGP or an IGP to detect 
link failures and reroute.  We don't want to run an IGP across an 
admin domain, and setting up and maintaining BGP is too complex for 
the customer.

Hence, the solution is to use BFD to check the liveness of the link 
and static routing.  When the link loss is (reliably) detected, the 
static routes become inactive, and are removed from PE rtr <-> rtr2 
iBGP/IGP, and the lower-priority static routes at backup routers get 
active.

Hope this clarifies.  If there are other ways to solve this problem 
(apart from using routing protocols or BFD), pointers are welcome..

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings