Re: regional ASN's

["Patrick W. Gilmore" <patrick () ianai net>]

On Dec 1, 2010, at 5:05 PM, Jack Bates wrote:
> On 12/1/2010 3:56 PM, Patrick W. Gilmore wrote:
> > Having islands which point default is not ugly.  They are probably pointing default anyway.
>
> If all sites strictly do default, fine. However, one could say static routing would work fine there too; and then you 
> don't need an ASN. If each site is multihomed (the usual reason to run BGP), you might want to see the routes to 
> apply appropriate traffic policies to them.

Just because you have one transit doesn't mean you shouldn't do BGP.  Consider the router at an exchange point with 
100+ peers and one transit, for instance.


> > If not, typing "nei $FOO allowas-in" is also not ugly, IMHO.
>
> Works, but you usually need to be careful when utilizing that method to prevent loops.

There is always a "you usually need to be careful" with any implementation, including a network without islands.

If this is, for instance, a bunch of remote offices with a single router & two upstreams each, there is zero risk of 
routing loops.  Otherwise, there are always considerations, whatever your topology choice.


> > But your network, your decision.  Mine runs fine like that.
>
> I'm surprised that you left out the obvious workaround and depending on the traffic, the most appropriate model 
> (leaving workaround status), create an encrypted channel between the networks and run iBGP over it.

If you think you need to be careful with allowas-in, you need to be an order of magnitude more careful with tunnels.

Plus I don't like GRE. :)

-- 
TTFN,
patrick