[quagga-users 7510] Re: redistributing a NAT'ted route

Andrew J. Schorr aschorr at telemetry-investments.com
Fri Sep 8 15:09:06 IST 2006


On Fri, Sep 08, 2006 at 08:59:07AM -0700, Collins, Richard (Com US) wrote:
> "And if not, is there some other way
> to accomplish this (to publish one route contingent upon whether
> another route is in the table)? "
> 
> I know with Cisco you can do under bgp 
>   neighbor x.x.x.x  advertise-map NAME1 exist-map NAME2
> The NAME's refer to ip prefix lists.
> 
> I didn't see anything equivalent in my version of Quagga.

Thanks for the pointer, that seems like it could work on IOS, but I don't see
it in quagga bgpd.  Do people think it's worth implementing?

Another possibility that occurred to me is to configure a
static route to the public subnet that I'd like to advertise
through a host on the private subnet that I'm mapping to.
Then I could redistribute the static route into BGP.  The
problem is that this would require a recursive nexthop
resolution on the static route, and my sense is that quagga
doesn't currently support this (but please correct me if
I'm wrong).  Also, this approach has the unfortunate side
effect of leaving an incorrect route for the public subnet
on this router.  In my case, that doesn't matter so much,
so it could work.

But overall, it seems to me that if we are using NAT
to translate the IP addresses, there ought to be a
comparable mechanism to translate the routes.

A fallback position is to have a simple shell script running on the side that
monitors the quagga routing table and uses vtysh to insert and withdraw the
route into BGP depending on whether the associated private route is available.
But this is certainly inelegant.

So I still have the same questions: is there currently
support in quagga for handling this kind of situation?
And if not, is it worth patching to add this?  And if so,
what would be the best way to add it?

Regards,
Andy


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