[nsp] /30 over WAN links

Ejay Hire ejay.hire at isdn.net
Fri Feb 6 10:58:35 EST 2004

On a related note, Cisco added support for /31's on serial
links somewhere in 12.2  If you are tight on IP space but
want to stick with numbered links this might be the way to


> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net 
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
Steve Lim
> Sent: Friday, February 06, 2004 9:33 AM
> To: cisco-nsp at puck.nether.net
> Subject: [nsp] /30 over WAN links
> Hello all,
> 	It has been an age old policy at my company to place
> /30 over the WAN 
> links ever since who knows when, and I've never really
questioned it. 
> But now, we've merged with another company, and they do
> follow such 
> a policy at the Access Layer. In fact, they use a /29 (or
> prefixes, if customer requires more IPs) over the WAN
links, and  use 
> the IPs not already used by the respective end interfaces
> hosts/devices on the remote/customer end.
> 	I had assumed that most, if not all companies use
> So this came as 
> a surprise. But more importantly, I can't come up with a
> reason why 
> we use /30s either.
> My questions:
> 1. At the Access Layer, what are the benefits of using
/30s, over 
> subnets with shorter prefixes.
> 2. Are there administrative benefits to such a policy?
> 3. Are there routing or switching benefits to such a
> 4. Is it a best practice policy?
> Thank you for comments.
> SL
> -- 
> <><><><><><><><><><><><><><><><><><><><>
> Steve Lim - Network Engineer (Michigan)
> Corecomm -An ATX Communications Company
> Support Bacteria, it's the only culture
> everyone has in common. -limmer
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