[nsp] /30 over WAN links

Steve Lim limmer at execpc.com
Fri Feb 6 14:38:01 EST 2004

Ah good question. And I think the question actually led me to an answer 
to my initial queries.

I suppose if we think long term, where customers might have changes in 
needs, it would make sense to number the WAN links with /30s. How messy 
would it be, if you began with a /29 or /28 over the WAN, and the 
customer's needs calls for more IPs? Worse, what if we started with a 
/27, and the customer downsized? What's the next move? Renumber to a 
preferred prefix? Sucky. Perhaps routing additional subnets would make 
sense, if you started of with a /29, and needed more. But on the 
converse, renumbering a /29 to a /30 because the customer has no need 
for the extra IPs, isn't the best idea. Especially if DNS and Email 
servers are on those IPs.

So, I am concluding that if I number the WAN with the most efficient 
subnet (a /30), I now have the option to add or subtract any size subnet 
per static routing. Simple, uncomplicated.

Many thanks all for the comments.


Rubens Kuhl Jr. wrote:

> Any scenario that would require or prefer numbered links nowadays ?
> Rubens

Steve Lim - Network Engineer (Michigan)
Corecomm -An ATX Communications Company
Support Bacteria, it's the only culture
everyone has in common. -limmer

More information about the cisco-nsp mailing list