Hi
The classic example from ACRC and BSCN is the case where you have multi OSPF
area's, you have two routers that are in area 0 but have no direct link. You
would configure a virtual path so that both routers are conntected in area
0.
It is also used with OSPF on a network to set the router ID and thereby
control the election of DR and BDR.
Loopback interfaces are also useful where a interface outage would be a bad
thing... they never go down, well there are power failures and admin goofs,
but otherwise they are always up/up.
In a lab enviorment they are wonderful for routing labs. They make it real
easy to add networks and making sure they are routed correctly. I guess this
could be a method of trouble shooting in the real world, but the are lots of
show and debug commands that I think would work better.
As for BGP, I am just now starting to get in over my head ;-) So the only
thing I know there is that the loopback address is used to set the router
ID, maybe more, more less, lots to learn on BGP here!
HTH
--
John Hardman, MCSE+I, CCNA
ArrisTech/CCS-IS SysAdmin
""m. jean stockton"" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> John;
>
> What are instances in which the following loop would be used?
>
>
> 1) Is a, virtual interface, for lack of a better term. They are often used
> with advanced routing, i.e. OSPF, BGP4.
>
>
> mjs
>
>
>
>
>
> HTH
> --
> John Hardman, MCSE+I, CCNA
> ArrisTech/CCS-IS SysAdmin
>
>
> <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > I was just wondering why you would waste a physical int. for a loopback?
> You
> > can create logical interfaces with the "int Loopback0" and so on. So why
> > would you take up a serial int unless you were using subinterfaces? I'm
> not
> > trying to be smart. I really want to know what or why this would be used
> > instead of logical int's. Thanks group.
> >
> > Mark Z. ~ CCNA (CCDA on Monday the 31st) :)
> >
> >
> > In a message dated 27.07.00 18:29:46 Central Daylight Time,
> [EMAIL PROTECTED]
> > writes:
> >
> > << just to let you know that you can set a loopback on a Cisco router
> from
> > the
> > router ?
> >
> > You must be in the priv mode not user mode to put the router in
> loopback.
> >
> > Router#
> > Router#conf ter ( hit enter )
> > Router(config)#int s0 ( hit enter )
> > Router(config-if)#LOOPBACK (hit enter )
> > Router(config-if)#end (hit enter )
> > Router#sho int s0 ( you will now see the serial interface in
loopback)
> >
> > To remove the loopback from the serial interface just reload the
router
> or
> > do this:
> >
> >
> > Router#
> > Router#conf ter ( hit enter )
> > Router(config)#int s0 ( hit enter )
> > Router(config-if)#NO LOOPBACK (hit enter )
> > Router(config-if)#end (hit enter )
> > Router#sho int s0 ( you will now see the serial interface out of the
> > loopback)
> >
> >
> >
> > Brian
> > Email Address [EMAIL PROTECTED] >>
> >
> > ___________________________________
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