[c-nsp] IP unnumbered question. Are isp's using this alot?

[Gert Doering]

Hi,

On Wed, Jun 22, 2005 at 09:45:48PM -0500, robbie wrote:
> Or use RFC1918 /31s for the ultimate in conservation.

Don't.

Using RFC1918 on transfer links on routers that send out packets 
(like "ICMP TTL exceeded") sourced from these links' IP addresses
violates RFC1918.

If you want transfer IPs, use real IPs - or use IP unnumbered, if you
decide that for your applications, the benefits of transfer IPs (pinging
customer routers on the WAN side, being able to telnet "connected" IPs
if the routing is messed up) do not outweigh the drawbacks (management
overhead, reverse+forward DNS, address usage, etc.).

We're using "ip unnumbered" on all statically-routed customer IPs, and
it works fine.  OTOH, we're not pinging CPE routers (but rely on
line-protocol keepalives to notice when a link goes down).

gert

-- 
Gert Doering
Mobile communications ... right now writing from * Isola dei Gabbiani *