Re: BGP over satellite link

[Brian Candler <B.Candler at pobox.com>]

On Sun, Apr 06, 2003 at 08:30:29AM -0700, Joe Joe wrote:
>    I am connected via a satellite link (SCPC/DVB). I have my border
>    router and definitely does my provider as well.

In that case, if your router can ping the far-end router with no intervening
IP hops, then you are "directly connected" as far as IP is concerned - even
if that "direct" link terminates several thousand miles away :-)

>    I dont have a /30 between me and my provider. I have my own address
>    space.

For a point-to-point link there are three possibilities:

1. a /30 subnet for the link, allocated from your provider's address space
2. a /30 subnet for the link, allocated from your own address space
3. the link is "unnumbered": it uses one of your IP addresses at your end,
   and one of your provider's IP addresses at the other end, and they are
   not in the same subnet.

Allocating a /30 for transit links is usually a good idea just because it
makes debugging simpler: e.g. a traceroute will show you exactly which
interface your packet went through. But unnumbered will work fine.

>    Is the bgp multihop option not a good choice for my config
>    settings??

BGP multihop is almost _never_ a good choice.

>    If it is, is it best to use my IP interface address or
>    loopback address?

In the absence of any reason to the contrary, I'd say:
- just use regular BGP peering, forget anyone mentioned multihop
- run the peering session between the interface addresses which have
  already been allocated for each end of the serial link.

Your provider might have reasons for wanting to do things differently, in
which case you should probably just go along with what they require. As long
as you have an AS number and a border router, and they give you their AS
number and border router IP address, you should be fine.

Regards,

Brian.

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