[c-nsp] BGP routes co-existing with different local-preference

[Andrew Fort]

David J. Hughes wrote:
> 
> On 26/10/2005, at 10:06 AM, Pete Templin wrote:
>> I didn't realize eBGP couldn't be done between loopbacks.
>>
>> router bgp ASN
>>  neig x.x.x.x disable-connected-check
>> !
> 
> Pete, of course it _can_ be done.  I think we all know enough about BGP 
> here to agree on that.  However I'm yet to see a single transit 
> provider who provisions eBGP between loopbacks.  I doubt they'd be 
> happy setting it up as multi-hop either.  Also, you will not be running 
> OSPF with their router so you wouldn't see their loopback fall out of 
> your IGP anyway.
> 
> 
> David
> ...

There are, of course, some providers who provision eBGP multi-hop 
sessions for when you want a full-view (i.e., their access router 
doesn't have the full table).  When I worked at a place that did this, 
we've built out "multihop 4" into configs and requested the customer 
static route the /32 of the loopback over their {/30,/31} to us.

There is also the case of multiple serial or PoS lines and load 
balancing over those, where you'll nail up with a loopback.  Same rules 
as above apply.

-andrew