[c-nsp] Sub-second Fast Reconvergence for OSPF?

[Gert Doering]

Hi,

On Thu, Mar 09, 2006 at 02:19:36AM -0800, Bruce Pinsky wrote:
> >> Also, if HSRP and GLBP could be 'BFD-enabled' ('BFD clients'?),
> >> that would be extremely useful. Static routes would also be neat.
> > 
> > I second the motion for BFD enabled HSRP.
> 
> Explain exactly what you are thinking here and I will see about submitting
> a feature request.
> 
> I'm not exactly sure what you are thinking since normally BFD is used to
> track the reachability of a nexthop adjacency and prevent forwarding into a
> blackhole should that neighbor go away.

If your HSRP setup ends up being partitioned (like in "VLAN mixup on the
intermediate switch", so all routers have a link, but one of the routers
can not reach the server(s)), the router will happily send out packets
via the non-working LAN interface.

BFD won't provide a solution, though, unless you have exactly *one* host,
and use BFD to influence interface up/down (so if you can't reach the
host, you set the interface to "down" and send packets to your partner
HSRP router via the "outside" links).

Generally speaking, being able to tie BFD to static routes or to 
interface status would be very helpful in all environments where you
need to detect end-to-end connectivity, but there is no useful link
status, due to "too many bridged ethernet devices in between".  DSL with
bridged ethernet links is another example where this would make much sense
(you can't trigger dial-backup based on interface status, as the interface
normally just won't go down if there is a problem "somewhere in the
carrier network").

gert

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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de