31 bit ptp link addressing?

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

If you go "huh?" take a look at rfc3021 - "Using 31-Bit Prefixes on
IPv4 Point-to-Point Links"



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 :slight_smile:

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.




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


Reported to work on the Alpine 3804, running software v6.2 .

Reported to work with sw v3.1 on the SE800, but apparently has been
in there for a while.