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
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