A loopback interface may be used for many purposes. You may use it as the
end of a tunnel on a VPN configuration or you may configure it just to have
a stable router-id for OSPF, for instance.
You don't need to configure it. They are optional and you may use any
address you want. If loopback intfs are following a specific address scheme
in your network, then they must be planned for some specific function by who
designed the network. You should not change it before knowing what function
is this (what may be achieved by analyzing your configuration carefully).
The subnet mask used on a loopback intf isn't also necessarily /24. This is
frequently used though, to economize address space, since you don't need to
differentiate network and host on this segment. In this case, host and
network are the same and routing is performed with no problem.
ER
CCNA
----- Original Message -----
From: "Susan Stone"
To:
Sent: Friday, June 22, 2001 7:22 AM
Subject: what is loopback interface for ? [7:9493]
Hi,
I always wonder what is loopback interface for? Can anyone explained its
function? Can we don't configure the loopback interface. Our WAN Lookback
always start with 192.168.X.X why? Must we use private IP? I found I can
telnet to a remote router using its loopback IP. But I wonder How I route
as it always have the subnet mask of 255.255.255.255. Then which is the
network and which the host
Susan
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