Point-to-point (/31) addresses

RouterOS Forwarding Protocols
61

It seems more accurate but it not works: Quagga is not sending OSPF hello.

62

Is there any fundamental reason why mikrotik does not support RFC 3021, so it is compatible with other vendors (cisco) without problems?

63

Same as with many other things here…
Hundreds of requests by many customers over years and they simple ignore it :frowning:

64

Hello,
Now that Mikrotik addressed the service providers segment with CCR routers, when does Mikrotik plan to support /31 networks?
The majority of routers used by service providers supports /31, so it will be hard to migrate from a previous /31 configuration to Mikrotik CCR routers.
Thanks,
David

65

Hi

Any News for this?

66

Brilliant :slight_smile:

67

Just a warning on using two /32 addresses as a workaround for the /31 problem.

We’ve had a number of problems with OSPF stability using this approach if you’re planning on using OSPF for a dynamic routing protocol.

68

Working on switching up some /30 to /32 in order to free up some addresses. So far haven’t noticed stability issues, but path selection seems a bit odd.
Here’s the rundown:
R1 is connected to R2. R1 interface to R2 has a /32 address, for example, 1.1.1.1/32 with network 2.2.2.2. R2 facing R1 is 2.2.2.2/32 with network 1.1.1.1. Connectivity seems OK, but in the routing table on R1, 2.2.2.2 shows up as directly connected, distance 0, but 1.1.1.1 doesn’t show up at all. No big deal, just a little odd.
Add R3 and R4. R1 → R2 → R3 → R4 → back to R1 and add OSPF. Now on the R1 routing table 1.1.1.1 shows up, but as an OSPF route with a distance of 110. Looking in OSPF routes, 1.1.1.1 has a path cost of 20 with a gateway of 2.2.2.2. Odd that a local address would have a path cost of 20, but things still seem to be working, so OK.
Here’s the potential gotcha - On R4 routing table the path to 1.1.1.1 has equal preference between going directly from R4-R1 and R4-R3-R2-R1. In the OSPF routes, both options have a path cost of 30 even though 1 path is 1 hop away and the other is 3. All the individual path costs are 10. A traceroute from R4 to 1.1.1.1 chooses the R4-R3-R2-R1 path. To be honest, I doubt I will be needing to connect to the IP address of a PTP link, and the path selection for the loopback address of R1 seems normal, but it is making me wonder if I want to proceed with more switching to /32s. I am thinking about tinkering with a static route on R1 to 1.1.1.1 to see what happens.

(FWIW, these aren’t the actual IPs I was using and haven’t tested it with these. Also, I doubt if it matters, but the lowest router id for path selection is R3, R4, R2, and then R1)

jw

69

Cisco /31 - MT/31 BFD not work
Cisco /31 - MT/32 BFD Work

70

serves the / 31 here in Italy is widely used on wan

71

/31 network between two mikrotik devices - here is how you do it

First thing - you do not actually use a /31 in the IP address ( this is important )

Here is how you use a /31 network of only two IP address to get two Mikrotik devices to talk to each other.

I am going to demonstrate 192.168.168.0/31 ( This /31 has only two IP address which are 192.168.168.0 and 192.168.168.1 )
Mikrotik #1

  • Configure IP address 192.168.168.0 on your first Mikrotik ( example 192.168.168.0 ( no / after IP address ) will be on ether2 )
  • Add the route 192.168.168.1 out interface ether2 ( use the interface name not an IP address )

Mikrotik #2

  • Configure IP address 192.168.168.1 on your second Mikrotik ( example 192.168.168.1 ( no / after IP address ) will be on ether2 )
  • Add the route 192.168.168.0 out interface ether2 ( use the interface name not an IP address )

Thats it , the two mikrotiks can ping each other and pass traffic

So , why burn up 4 IPv4 address on a link with only two Mikrotiks on the link. Each /30 link between two Mikrotik devices can now be used for two different /31 links ( twice as many link using the same number of IP address ).

North Idaho Tom Jones

72

@TomjNorthidaho, some creative thinking there, I might pop your balloon though :slight_smile:
That method is called point to point addressing and but should work

73

One thing I have not tested is a /31 between a Mikrotik and a Cisco , or between a Mikrotik and a PfSense virtual router/firewall.

North Idaho Tom Jones

74

The main issue that i’ve run into with this method is routing protocol instability. I’ve had intermittent issues with OSPF adjacency instability on a number of networks that used this addressing method. As soon as we migrated to /30 or larger prefix, the issues went away.

75

I wish that Mikrotik would support a /31 natively on a /31 network between any two Mikrotiks.
With IPv4 exhausted and no more new IPv4 blocks available, it is becoming increasingly important-urgent-required to natively support /31 networks , without the need to do any fancy work-arounds.
I’ve run into several problems with peer-connections where a remote party is wanting to use a /31 ( a /31 network for BGP peering ). I gave up trying to make it work and had to fight to use a /30 for BGP peering - what a friggen nightmare that was !

North Idaho Tom Jones

76

So I am on the verge of setting up a BGP with my 1st peer and he mentioned using a /31. I am going to assume he is using a Cisco. I am a Mikrotik shop.

You are saying that Cisco and Mikrotik are not able to use BGP on a /31?

Rick

77

When I was adding a second BGP peer, I was given one IP address from a /31. I had a Mikrotik ( I don’t know what the upstream BGP router was ). I tried and tried and tried using a /31 and at the time I could not get it to even ping his /31 IP address. This was my first attempt at trying to use a /31.
As a test, I switched to a Cisco router and the /31 worked , but I wanted to use a Mikrotik router for my BGP. I was finally able to get the BGP peering network changed from a /31 to a /30 and suddenly everything started working on my Mikrotik router.

Sooo , although it might be possible to make a Mikrotik function on a /31 network for BGP peering, I suggest using a traditional /30 network for BGP peering. A /30 network for BGP peering will give you the ability to change your Mikrotik BGP peering router to any other BGP peering router. If you setup a /31 network for BGP peering , then you might get stuck to only being able to use routers which natively support /31 networks for BGP peering.

So , IMO - for BGP peering , I suggest using existing traditional tried-and-true /30.

North Idaho Tom Jones

78

Of course when you have only a simple peering with some other world where they are using /31, you can just change your own side to be a /30 or even larger to
make your side contain the addresses from the /31 and neither of them being the “network” or “broadcast” address on that subnet.
This will make some addresses unreachable, but when the /31 is from a range that is just used for such peerings, that usually does not matter.

When you want to setup your local shop using /31 and have a mix of routers that allow that and MikroTiks that don’t, this could be more of a problem because there
is more risk fo connectivity issues in that case.

79

Any movement on this? Every IP Transit provider I’ve looked at provides a /31.

80

turnip, this should resolve all issues: http://forum.mikrotik.com/t/point-to-point-31-addresses/29492/1