Re: The need of Loopback0 Interface on A Router !!!
1) If you want to change your router ID (example for OSPF) but you can't renumber a physical interface. It is also good for peering in BGP and DLSW+, as the interface never goes down (unless you admin down it), and if your peer has multiple paths to you, they peer with the loopback so that if one path dies, you are still peered. They can also be used in almost any situation you want if you always want the interface to be up (eg Ipsec tunnel).
2) The dialer interface borrows the loopback's address. Packets are sent with a source IP of the loopback, and the loopback is routerb's next hop.
3)No, the loopback on routerb would have to be on a different subnet or you have routing problems. Ip unnumbered requires both ends of the link to be unnumbered though.
4) Not sure what you are getting at but, No they are not related.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...