Point-to-point connections using /32 addresses

[spj2019]

Hello, 

We are going to implement a point to point connection between two devices and I've been told to use /32 addresses at both ends. One is a Cisco 3650 with L3 routing enabled. I'm basically stuck at step one : I'm not able to define a /32 address because IOS tells me it's invalid on vlan interfaces. Only loopbacks are accepted with that kind of netmask. Is it me or do I have a problem with my specifications? I've always used /30 addresses for point-to-point connections...

Thanks for any help! 

[Uwe Engberg]

For a Point to Point Connection you should use /30. A /32 address contains only one IP address so it wont work.

Regards

[johnd2310]

Hi,

Are you referring to /31

https://tools.ietf.org/html/rfc3021

Thanks

John

[spj2019]

Hello,
thanks for your prompt reply. We are currently attaching two 3650 L3 routing switches, connecting port 24 on one device to port 24 on the other. Basically, we'd like all devices to have the same type of configuration so that every 'branch office' would be organized in the same manner. The goal is to be able to plug in any two switches and have them working as needed, with minimum configuration changes. Since we couldn't define the /32 netmask on the VLAN Interface, we opted for a /16 so that any 10.100.0.0/16 IP address should connect without problems. 

[Georg Pauwen]

Hello,

on a side note, ISPs use, as far as I recall, /32 masks on PPPoE/PPPoA connections with IP addresses dynamically assigned to dialer interfaces, where the address is used as an endpoint identifier, the purpose being IP address conservation...

[paul driver]

Hello

You dont mention how these devices are to be connected, Physically or logically, Also you mention a switch and vlan interfaces , So can you confirm what the other device is and how it going to be connected, are you using any routing protocols?

FYI -You can indeed use /32 addressing to establish a "connection/peering or adjacency" between two devices however doing so would involved an underlying igp or static addressing which would not have a /32 addressing.