On 6/6/03 10:05 AM, "m.rapoport@completel.fr" <m.rapoport@completel.fr> wrote:
I was wondering what are the choices made by Service Providers on the loopback addressing. The context is an IP/MPLS Backbone providing both Internet and BGP-VPN services.
If the BGP Identifier, which is used for connection collision resolution and path selection (among others seemingly random things) conflicts you'll have issues. In my experience even mediocre IP addressing frameworks typically don't have issues with RIRs when space is appropriately justified (i.e., there typically aren't issues with loopback and inter-router address space justification). What I'd be more concerned with is loopback IP allocation and it's effect on aggregation, stability, and other network policies (e.g., source-interface type stuff). For example, using a single contiguous block for all loopback IPs significantly simplifies filtering policies. OTOH, you may opt to provide more optimal aggregation and allocate loopback IPs from the same block as p-t-p IPs (per router, POP, region or other) such that less information needs to be carried internally in your IGP (or BGP). RFC 2519 provides some guidelines for inter-domain route aggregation. A slew of other documents and books provide IP address allocation guidelines as well. -danny