Setting IPv4 address with /32 subnet mask on Gig Interface

[Yassin Alizadeh Golbazi]

Hello

I want to set IP add with 255.255.255.255 subnet mask on gig interface on cisco 2811 router.

I set address directly on interface also set address on lo interface and unnumbered on gig interface

in both type router do not allow to set address

if there is a way to set /32 address on gig interface, please tel me

thank you

[luis_cordova]

Hello @Yassin Alizadeh Golbazi,

https://www.cisco.com/c/en/us/support/docs/ip/hot-standby-router-protocol-hsrp/13786-20.html

In this link I found this:

The only real disadvantage that the unnumbered interface suffers from is that it is unavailable for remote testing and management. You should also remember that the unnumbered interface should borrow its address from an interface that is up and running. If the unnumbered interface is pointing to an interface that is not functional (that is, which does not show "Interface status UP", "Protocol UP"), the unnumbered interface does not work. This is precisely why it is recommended that the unnumbered interface point to a loopback interface since loopbacks do not fail. Finally, remember that the ip unnumbered command works on point-to-point interfaces only. When you configure the command on the Multiaccess interface (that is, Ethernet) or the loopback interface, the following messages are displayed:

RouterA(config)# int e0 
RouterA(config-if)# ip unnumbered serial 0 
Point-to-point (non-multi-access) interfaces only 
RouterA(config-if)# ip unnumbered loopback 0 
Point-to-point (non-multi-access) interfaces only  

[Richard Burts]

Luis provides some insight into why attempting to use ip unnumbered did not work. So +5 for that.

But the original poster says that in addition to trying to use ip unnumbered he also attempted to configure the IP address and mask directly on the interface and it did not work. I would ask why he attempted to use a /32 address on a Gig interface. The /32 says that this address is the only address on the segment. It makes sense to use that on a loopback interface (where it is not possible to have any connected neighbor). But why configure a Gig interface in a way that it is not possible to be connected to anything? I am not surprised that this did not work.

HTH

Rick