Loopback interface is a software simulated interface. It allows routers to simulate the existence of more networks without having to have a physical port. When adding a loopback interface to a router use the following command format:
Router(config)# interface loopback 0
Router(config-if)# ip address 10.1.1.1 255.255.255.255
Router(config-if)# no shut
Notice that the loopback is assigned a port number. You can add many loopbacks to one router using the port assignment. Also note the subnet mask that is 255.255.255.255, you should use this mask so that it turns the loopback into a host address.
Null interface is an interface that never goes down and does not exist. You will use this in lab scenarios to simulate other networks. You can use this when setting a static route by adding it to the end of the command instead of a real interface.
Redistribute static is added the router rip configuration to tell RIP to distribute all of your static routes to other RIP routers.
RIP version 2
The only difference when comparing RIPv1 and RIPv2 data are the two fields that immediately follow the IP Address field. In RIPv2 they are filled with: Subnet Mask and Next Hop Address.
A router running version 1 has the ability to receive version 2 messages because they are almost exactly alike. The router will just ignore the version 2 information (subnet mask, next hop address). To turn version 2 on you enter the following commands:
Router(config)# router rip
Router(config-router)# version 2
To change from version 2 to version 1 you enter the command no version. To prevent RIPv2 from performing automatic route summarization (classful) you need to issue no auto-summary.
RIPv2 sends data on the multicast address 126.96.36.199 meanwhile RIPv1 sends it on the broadcast address 255.255.255.255.
Authenticating Routing Updates
Routing Protocols that Authenticate:
Authentication is not encryption it just prevents a router from accepting information from other routers that do not have the correct password or key.
We do not discuss RIP authentication configuration but feel free to look up the configuration process.