Hi all,
Just (mostly) out of personal curiousity - is anyone here running any
PtP links using 31 bit prefixes rather than the /30's we're all happy
with?
If you go "huh?" take a look at rfc3021 - "Using 31-Bit Prefixes on
IPv4 Point-to-Point Links"
Thanks,
Adrian
Some providers even use /31s on peering interfaces
if the other side can also. Most modern router software
supports this feature.
- jared
Summarising the few private replies I've had:
* a few people did reply saying that they're using it successfully
* someone reported that it worked successfully on 12000 and some 7500 series
routers, running a 12.0S train IOS
* someone else reported that any IOS train that has been eligible to receive
"new features" in the last 9 months will have /31 bit PtP support
* I can add that vendor N's broadband concentrator doesn't allow you to
add a /31 (they actually let you assign up to /30, then /32 to an interface 
I hope this is of some interest to the list members.
If anyone is running /31's on PtP links on vendor J's equipment, I'd like to
hear from you.
Adrian
Update:
Juniper:
Works in 5.x trains. Works in 4.x trains, but there's been a report
that /31 support is broken in 4.4R2.3
Extreme:
Reported to work on the Alpine 3804, running software v6.2 .
Redback:
Reported to work with sw v3.1 on the SE800, but apparently has been
in there for a while.