I have two routers attached directly and both of them has loopback address. The interface has no IP address, I have just connected R1 g0/0 to R5 g0/0. If I put IP address on the g0/0 interface of both routers then I can ping between loopback addresses but if I remove the IP addresses from the g0/0 then I cannot ping.
Does loopback need interface with IP address to ping one another?
sh ip route of R1
Gateway of last resort is not set
10.0.0.0/32 is subnetted, 1 subnets
C 10.1.1.1/32 is directly connected, Loopback1
sh ip route of R5
Gateway of last resort is not set
10.0.0.0/32 is subnetted, 1 subnets
C 10.1.1.5/32 is directly connected, Loopback5
sh run
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname R5
!
ip cef
no ipv6 cef
!
license udi pid CISCO2911/K9 sn FTX15246RHB
!
spanning-tree mode pvst
!
interface Loopback5
ip address 10.1.1.5 255.255.255.255
!
interface GigabitEthernet0/0
no ip address
duplex auto
speed auto
!
interface GigabitEthernet0/1
no ip address
duplex auto
speed auto
shutdown
!
interface GigabitEthernet0/2
no ip address
duplex auto
speed auto
shutdown
!
interface Vlan1
no ip address
shutdown
!
ip classless
ip route 10.1.1.1 255.255.255.255 GigabitEthernet0/0
!
ip flow-export version 9
!
line con 0
!
line aux 0
!
line vty 0 4
login
!
end