-----Original Message-----
From: Jason Roysdon <[EMAIL PROTECTED]>
Newsgroups: groupstudy.cisco
To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Date: Tuesday, November 28, 2000 4:25 PM
Subject: Re: question about loopback interfaces
We generally have a class C range set aside for loopbacks for most customers
with networks of any size. I can only think of one reason to not assign it
as a host route (ip with 255.255.255.255 mask), and that's for policy
routing (required when you're doing NAT Pools + Static NATs + VPN so that
your Static NATs can hop around the VPN tunnel to the outside interface).
--
Jason Roysdon, CCNA, MCSE, CNA, Network+, A+
List email: [EMAIL PROTECTED]
Homepage: http://jason.artoo.net/
Cisco resources: http://r2cisco.artoo.net/
""whitaker"" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Thanks for the response! I have two more questions:
>
> If in an OSPF and BGP environment, I think can see the stability with
> loopbacks... Correct me if I'm wrong in this theoritical scenario:
> Two routers in an OSPF share the highest priority. To break the tie and
> determine the DR, OSPF looks at router id, which is the highest interface
> address (let's say serial interface) and determines a particular router
has
> the highest id. It becomes DR. Without a loopback address, if the serial
> interface goes down, then the BDR comes online and a new BDR election
takes
> place. This requires processing power and could slow down the network.
> With a loopback interface configured with the highest IP address, then if
a
> router is the DR and looses its serial interface, it would remain the DR.
> Is this correct?
>
> My second question involves the configuration of the loopback from
> real-world experience. What do most of you use - an address from the same
> subnet one of the interfaces is on or a seperate address?
>
>
>
>
> -----Original Message-----
> From: Tony van Ree [mailto:[EMAIL PROTECTED]]
> Sent: Monday, November 27, 2000 9:28 PM
> To: whitaker; [EMAIL PROTECTED]
> Subject: Re: question about loopback interfaces
>
>
> The notes I have here suggest that using a loopback interface provides a
> more stable interface than a physical interface. As the loopback
interface
> is up as long as the RAM is working the chances of losing this interface
are
> greatly reduced.
>
> Both OSPF and BGP use the highest active IP address as the router ID. If
a
> loopback address is configured they will use the loopback address.
> Therefore the loopback address provides more stability.
>
> It can also make network management and troubleshooting tasks easier.
>
> Teunis.
> On Monday, November 27, 2000 at 08:58:00 PM, whitaker wrote:
>
> > Could someone explain the importance of using loopback interfaces? I
keep
> > reading that it is important when using routing protocols to use
loopback
> > interfaces. A consultant that is writing documentation for me suggested
I
> > obtain an entire class C network just for loopback addresses. Cisco
says
> > when configuring BGP that, "We recommend you use a loopback interface to
> > guarantee reachability in networks with multiple paths." (from
> > http://www.cisco.com/warp/public/459/23.html#3).
> >
> > Maybe I'm missing something totally obvious here, but exactly what
benefit
> > do I gain from using loopback addresses? I know it is supposed to
provide
> > reliability for routing protocols, but how?
> >
> > _________________________________
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> >
> >
>
>
> --
> www.tasmail.com
>
>
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