default route via OSPF depending on the ISP

[Ondrej Zajicek]

On Thu, Dec 03, 2015 at 02:34:02PM +0000, Rohrmann Sascha wrote:
> Dear users of the Bird internet routing  daemon,
> 
> First of all I am sorry for my e-mail which I have sent some minutes before.
> It was a mistake and you can ignore my last mail.
> 
> Now to my question:
> 
> I want my OSPF to distribute the default-route ONLY and ONLY if the ISP is available.
> Means, if the link, or the IP isn't available, my OSPF should be quite.
>
> Further information:
> 
> ISP                         (ISP is up)
>   l                            (Link is up)
> R1                          (Interface is up)
> 
> R1: everything is ok, I can reach the ISP, so I am the default-gateway for everybody below me.
> 
> ISP                         (ISP is down)
>   l                            (Link is up)
> R1                          (Interface is up)
> 
> R1: Oh gosh! The ISP is down! I am now no longer the default-gateway for everybody below me.
> 
> ISP                         (ISP is up)
>   l                            (Link is down)
> R1                          (Interface is up)
> 
> R1: Oh, I can't reach my ISP... Ok, I need to stop telling everybody below me I am the default-gateway.

Well, you could use static default-route and 'check link' option, but
that will help you only in the third case, not in the second one. For the
second case, you must have some other way to establish whether ISP is up
or down, either by running some routing protocol between you and ISP,
or running BFD session.


> I was thinking about the bfd protocol, but bfd is kinda new and you can't run more than one instance in bird.

Well, is there any reason why to run multiple BFD instances in BIRD?


-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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