Up to thirty-two IP addresses are supported on a loopback interface. You can configure multiple IP addresses on a loopback interface ( lo0 to lo7). In the same way, if you configure a loopback interface ( lo1) with IP address 172.16.101.8, you cannot configure another loopback interface ( lo2) with IP address 172.16.101.8. This means that the address cannot be used by a VLAN interface or another loopback interface.įor example, if you configure a VLAN with IP address 172.16.100.8/24, you cannot configure a loopback interface with IP address 172.16.100.8. The maximum number of IP addresses supported on a switch is 2048, which includes all IP addresses configured for both VLANs and loopback interfaces (except for the default loopback IP address 127.0.0.1).Įach IP address that you configure on a loopback interface must be unique in the switch. Loopback interfaces share the same IP address space with VLAN configurations. L 10.0.2.1/32 is directly connected, FastEthernet1/0Ĭ 10.0.3.0/24 is directly connected, FastEthernet1/1 L 10.0.1.1/32 is directly connected, FastEthernet0/1Ĭ 10.0.2.0/24 is directly connected, FastEthernet1/0 L 10.0.0.1/32 is directly connected, FastEthernet0/0Ĭ 10.0.1.0/24 is directly connected, FastEthernet0/1 + – replicated route, % – next hop overrideġ0.0.0.0/8 is variably subnetted, 13 subnets, 3 masksĬ 10.0.0.0/24 is directly connected, FastEthernet0/0

O – ODR, P – periodic downloaded static route, H – NHRP, l – LISP Ia – IS-IS inter area, * – candidate default, U – per-user static route I – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2Į1 – OSPF external type 1, E2 – OSPF external type 2 The loopback interfaces are not in the routing tables because they are in the 192.168.0.0/24 range which has not been included in the routing protocol.Ĭodes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGPĭ – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area There is no connectivity from the PCs to the loopback interfaces because they are not in the routing tables of the routers (apart from the local loopback interface on each router). Is there connectivity to the loopback interfaces from the PCs? Why or why not? We can get to our routers no matter what path we’ve got available and still using the same IP address.Ģ. I can still ping 192.168.1.1and if I traceroute to it, I’m going to see it going down the bottom path via R5. However, it failed over to the other path, so it uses the FastEthernet 2/0. If I do a show ip route now, I can see the 192.168.1.1 in the routing table from EIGRP. The first path is not going to be available anymore. On R4, I’ll go to interface FastEthernet 0/0 then I’m going to shut down that interface.

A loopback interface is a logical interface and it allows you to assign an IP. Let’s check that I can failover and could use the loopback. In this Cisco CCNA training tutorial, youll learn about loopback interfaces. I can ping 192.168.1.1and if I enter the command trace 192.168.1.1, I can see that it’s passing along the top path with the next hop of 10.1.1.2 which was out interface FastEthernet 0/0. That’s why only the FastEthernet 0/0 path is in the routing table right now. There are two paths, but one of them has got a better cost. Let’s see if the route is there using the show ip route command. Going back to R4, EIGRP converges pretty quickly. The 0.0.0.0 is the wildcard mask which is the inverse of the subnet mask.

Standard loopback address