[j-nsp] Am I carrying this route or not ?

[Payam Chychi]

Hey, 

I suggest grabbing a book on routing and ip fundamentals but here is a basic overview

You get routs, you install routes, you pass routes... So what does this mean?

Every protocol exchanges routes but before it makes them "active" it must run its specific algorithm to ensure best path is selected (most cases this is a single path however larger or more advance networks might have eclb or even un-eclb"). When the best path is selected its then installed in your routing table and becomes active. 

Be careful to not mistake a passed route with an installed route (inactive/active). Ex. if you look at a nei bgp table for received routes, you are seeing what they are advertising to you, some or all may be active if they are best paths.

Number of reasons why a route may not activate: invalid/unreachable next hop (including down vlans and interfaces) better AD, better metrics... 

Normally if you have a simple network then you can look at the output of your routing table and any valid route well be marked by a "*" beside it, along side bunch of other information about the origin of the route

Hope this helps. Make sure to google before making changes... Or at lease do "commit confirm 60" which will revert your changes after 60 seconds in case you blow up your network and lose access. 

Cheers, 

-- 
Payam Chychi
Network Engineer / Security Specialist


On Saturday, 23 March, 2013 at 4:26 PM, Jeff Wheeler wrote:

> On Sat, Mar 23, 2013 at 5:21 PM, Zehef Poto <mpdechets at gmail.com> wrote:
> > I just inherited our backbone. We're a small LIR, we have an AS. The
> > backbone consists of four MX80 routers, all acting as eBGP edge ones (there
> > are various IP transit links up and running on all of them). I also use
> > OSPF adjacencies, and iBGP. Again, all of this is very new to me, so I'm
> > learning little by little. Sorry about possible mistakes/errors.
> > 
> 
> 
> I think you had better get some help before you break your network!
> 
> > The question is : how can I check if a particular route is being carried in
> > my backbone ? How can I make sure that's not the case ? I'm being suggested
> > to "use next-hop-self", but for some reason I can't fully understand what's
> > involved here...
> > 
> 
> 
> In the CLI, use the command:
> show route 192.0.2.0/24
> Hit ? for options such as exact, detail, etc.
> 
> Whoever that person is that said something about "use next-hop-self"
> in this context, either you misunderstood them, or you shouldn't
> listen to them anymore. That has nothing to do with looking to see if
> your router knows about a route.
> 
> -- 
> Jeff S Wheeler <jsw at inconcepts.biz>
> Sr Network Operator / Innovative Network Concepts
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