[j-nsp] Route Reflecting & Next-Hop Self

[Dan Armstrong]

I was trying to make a generic policy statement that I could deploy 
across all our boxes... this is not possible if we name ebgp peers 
specifically, and if we change transit providers - we have to keep track 
of changing policy statements as well... kind of messy.



Chuck Anderson wrote:
> On Thu, Sep 04, 2008 at 10:08:45PM -0400, Dan Armstrong wrote:
>   
>> In IOS, if I set next-hop self in a neighbor relationship with an  
>> RR-Client, it sets the next-hop to itself for routes learned from local  
>> eBGP sessions, but leaves the next-hop unchanged for routes that it's  
>> passing on from other fellow route-reflectors...
>>
>> The *problem* is that in JunOS, if I set next-hop self on a neighbor  
>> relationship with an RR-Client, it sets the next-hop to itself all the  
>> time, even on routes it's passing on from other fellow route-reflectors,  
>> effectively sucking all traffic into the route reflector and totally  
>> defeating the purpose of route reflecting.
>>     
>
> That's just the way it is in JunOS--not much policy-related behavior 
> is hard-coded into JunOS like it might be in other vendors.  This 
> gives you the most flexibility in writing policy to do exactly what 
> you want.
>
>   
>> Now, of course we can policy-statement our way out of this - with big  
>> messy kludgey stuff, but it seems to me that there has to be a fairly  
>> simple and elegant way to do this, since it's pretty common, no?
>>
>> (My current kludge is to set an import policy on my eBGP sessions that  
>> tag each route with a community called "HERE", have an export policy  
>> towards all my iBGP neighbors to set next-hop self if the route is  
>> tagged with the community "HERE", then strip it off - so that the  
>> community "HERE" never leaves any box.)
>>     
>
> That is one recommended method.  The other is to match the eBGP 
> neighbor and only apply next-hop self to routes from your eBGP peers.
>
> e.g. in your IBGP export policy (from the JNCIP study guide):
>
> term 3 {
>     from {
>         protocol bgp;
>         neighbor [ 172.16.0.14 172.16.0.18 ];
>     }
>     then {
>         next-hop self;
>     }
> }
>
> where 172.16.0.14 and 17.16.0.18 are eBGP peer addresses.
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