[c-nsp] BFD w/ static routes

[Bruce Pinsky]

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Pekka Savola wrote:
| 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..
|

Whether there are other ways or not depends on what the underlying media is
and on what platform it's implemented.  Is the CE attachment of one
particular media type or does it run the gamut?

- --
=========
bep

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