06-25-2010 05:08 AM - edited 03-06-2019 11:45 AM
Hi,
In my campus, i saw that there is loopback interface on the cisco switch/router. Actually I am not really understand what is loopback interface and why this interface configured on the switch/router. Can anyone help me on this?
06-25-2010 06:08 AM
Hi,
In my campus, i saw that there is loopback interface on the cisco switch/router. Actually I am not really understand what is loopback interface and why this interface configured on the switch/router. Can anyone help me on this?
If the loopback interface on a router is down, that means the router is unavailable as a whole.In contrast, a physical interface being down does not mean the router itself is out of commission. A router's ethernet port can go down, but the other physical interfaces on that router are still operational. Since a loopback interface is logical, there's nothing physical that can go wrong with it.
Hope to Help !!
Ganesh.H
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06-25-2010 07:17 AM
It is a must to configure the loopback interface on every switch/router?
06-25-2010 07:24 AM
Its not mandatory to configure loopback on router and switches. For some protocol like Ospf and Bgp, we can assign router ip address by using loopback address.
So its optional for small deployment and can be used for testing in lab environment but when you go for BGP , it helps us for more control, like adding neighbour with loopback.
06-25-2010 07:28 AM
OK Generally we used to have loopback for various purpose in network and
see below exaplantaion on usage of loopback inetrface.
A loopback interface is also known as a virtual interface, in that it is
always up and is available after it has been configured. A loopback
interface is often used as a termination address for some routing
protocols, because it never goes down.There is another common use of
loopback address, that is to identify a router, for example ?If you wanted
to identify a particular router on your network to check if that router is
up. You know that the router has e0 interface with IP address 10.10.1.1
and you try to ping this IP but don?t get a response!!
So, is the router down? Well, it?s possible that the router is up and that
the ping reached the router on another interface, but you didn?t get a
response because e0 is down. To find out exactly if the router is up
you?ll have to ping another interface but that interface might be down too
and therefore causing the same scenario to happen.To get around the above
problem, you can create a loopback interface on the router with a unique
address, and then when you try telnet or ping to the configured loopback
interface?s IP you?ll always get a response no matter how the packets
reached the router.
There are other circumstances were the loopback interface might be handy
are the following:
-using ?unnumbered? cmd on serial links mixed with the loopback interface
to eliminate wasted IP address on serial links.
-Various routing protocols such as OSPF/BGP make use of ID, which should
be the link that is always up, therefore the loopback interface is greate
for this purpose.
-Loopback interface is also great to use with Management software, in
that, Management software will test whether the router is alive by pinging
the loopback interface IP address.
Hope to Help !!
Ganesh.H
Remember to rate the helpful post
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