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Re: OpenBGP nexthop



On Wed, Apr 12, 2006 at 01:36:46PM +0200, Sylvain Coutant wrote:
> > What was the state of the parent interface and what kind of interface is
> > it?
> 
> Bge driver. It was up and running : BGP sessions were established
> through the vlans reported as invalid by OpenBGP.
> 

I bet Henning's diff will fix this.

> 
> > ifconfig down should not crash the box. Panic message and trace would be
> > interesting.
> 
> It was remote and we did a hard reboot without console access. Log files
> were empty.
> 

Bummer.

> 
> > No, the session and the nexthop are two different things.
> 
> I agree. My point is : how to prevent routing loops in such cases ?

How should routing loops happen if you do not announce those invalid
routes? Prefixes with an invalid netxhop are not used and are not
redistributed.

> Whatever triggered the case (a link down for any reason or a bug) is not
> so important. Announcing routes over the Internet and creating a routing
> loop for those routes is important.
> 
> It could be one more setting that, if set to yes, would drop the session
> if it receives an unreachable nexthop ... just an idea. It could default
> to yes for eBGP session and no for iBGP sessions. Would that fit most of
> "usual" cases ?
> 

No way. This is not how BGP works and will break in many cases.

-- 
:wq Claudio



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