People where talking about /31’s not being useable on Mikrotiks quite a while ago.
It is not like they are new in the internet world at all but when I was testing them even on recent software versions /31’s would not work.
With IPv4 being in short supply these dating using 2 IP Addresses on a PTP link instead of using 4 ( a /30) does make sense and I would love to know if there is a time frame they will work as nearly every other people of hardware supports /31’s..
Why not mikrotik?
Craig
Same thing here, but I don’t forcing this because I can live with /30s and IPv6 is coming and knocking on the window 
You can do /31 on Mikrotik.
Set interface to 10.99.99.1/32 and set broadcast to the remote end e.g. 10.99.99.2 do the opposite on the remote end.
It is not clear to me. Can you please give us a config example?
Thanks,
oreggin
Umm.. that is a work around (hack) for Mikrotik → Mikrotik as far as I know as /31 are broken.. doesn’t work as far as I could tell with anything else which talks /31 properly.
Ok, but what if I need to work with non-MT/RoS devices like cisco?
/31 subnetting seems in my opinion a little odd and should not work on an interface, it should work only on defining routes to get 2 IPs at once…
Rationale:
A network needs a network address, a broadcast address and an usable network host IP range…
Now subnetting using /31 gives you just 2 addresses, and since the lowest will be the network address and the highest the broadcast, there is no room for usable addresses in a /31 subnet.
Thus the smallest functional subnetting on an interface would be /30. And nothing is broken, just working as expected.
And the so called “hack” presented by nz_monkey is the solution for that particular setup, not a workaround.
/31 doesn’t brake too. Please see RFC3021.
@oreggin: You are right. Missed that one…
And it is logic - what is the use of a broadcast and network address in a 2 IP network 
Now if MT implements it - that’s another question.