That amount of configuration is not necessary. Besides, I've never seen
a serial line configured to be a backup interface in that way, but if
it's possible and if it behaves like other async interfaces, it will be
placed in a down state until the primary interface goes away.
If you have two serial connections between two routers you'll
automatically have load-sharing and redundancy without any additional
configuration.
To share load on a packet-by-packet basis, turn off fast switching on
both interfaces (no ip route-cache). If you want to load share on a
per-destination basis, make sure fast switching is turned on on both
interfaces.
To test this, if you have two routers and two back to back cables,
attach them and set up your addressing, datalink layer encapsulation,
and clocking. You can use either HDLC or PPP, or even frame relay if
you wanted to. Make sure both links are in separate subnets.
For routing, you can either use two equally-weighted static routes or
the routing protocol of your choice. Because both paths are the same
cost, the router should install both routes into your routing table.
Traffic will automatically load-share across those links and they'd be
completely redundant if one link were to fail.
HTH,
John
>>> "Vijay Ramcharan" <[EMAIL PROTECTED]> 3/21/01 9:31:10 AM >>>
To revisit this question from yesterday, could the following be done
and
what does it accomplish, if anything?
The question posed is below.
"Jason Stephens" <[EMAIL PROTECTED]> wrote in message
998ndv$1fh$[EMAIL PROTECTED]">news:998ndv$1fh$[EMAIL PROTECTED]...
We have a situation where we want to have 2 t1's going to another
office.
We want these 2 t1's to not only provide redundancy in case 1 goes
down, but
also want them to load balance while they are both up.
So basically, we want the two t1's to be up providing 3 mpbs of
bandwidth
and if one goes down for it to automatically send all traffic to the t1
that
is still up. We have 3600 series routers on both ends. Can this be
done? If
so, please explain how. I looked into the Multilink PPP stuff, but it
seems
to be only for async ports. Thanks for any info in advance!
Is this possible to achieve using the solution below?
Use a "backup interface" command along with "backup load" and "backup
delay"
commands to achieve redundancy and
load balancing. Both T1's are correctly configured and are connected
to the
same router. Static routes are used for each T1 using "ip route
0.0.0.0
0.0.0.0 <next-hop-address>".
By my reasoning, by using the backup interface command on the primary
line,
if the primary line goes down the second line is used automatically to
route
traffic.
If the primary line exceeds the load specified by the "backup load"
command,
the second line is put into use automatically.
The "backup delay" command just tells the router to stop using the
second
line when usage on the primary line drops below the predefined load.
Any input would be appreciated. Thanks.
Vijay Ramcharan
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Vijay Ramcharan
Sent: Tuesday, March 20, 2001 6:34 PM
To: [EMAIL PROTECTED]
Subject: RE: Multiple T1's
In this scenario, is it possible to use a "backup interface" command
along
with "backup load" and "backup delay" commands to achieve redundancy
and
load balancing? Providing that both T1's are correctly configured and
are
connected to the same router?
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Howard C. Berkowitz
Sent: Tuesday, March 20, 2001 5:39 PM
To: [EMAIL PROTECTED]
Subject: RE: Multiple T1's
At 02:12 PM 3/20/2001 -0800, you wrote:
>If you are running EIGRP as your routing protocol, it will take care
of the
>load balancing for you without the added complexity and CPU overhead
of PPP
>multilink.
>
>There are some great EIGRP config guides on CCO.
>
>Chris Lemagie
I don't understand what advantage EIGRP would give. First, no
routing
protocol load balances. It is the routing table
task that makes the final decision about load balancing, with the mode
dependent
on the switching modes of the output interfaces.
Second, any routing protocol, except standard BGP (i.e., without Cisco
extensions) and
OSPF externals, can produce equal-cost routes eligible for load
balancing.
EIGRP and IGRP can produce unequal-cost routes eligible for load
balancing,
but the media here specifically are equal cost
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf
Of
>Brian
>Sent: Tuesday, March 20, 2001 1:57 PM
>To: [EMAIL PROTECTED]
>Subject: Re: Multiple T1's
>
>
>On each end, static route traffic out both interfaces.
>
> Bri
>"Jason Stephens" <[EMAIL PROTECTED]> wrote in message
>998ndv$1fh$[EMAIL PROTECTED]">news:998ndv$1fh$[EMAIL PROTECTED]...
> > We have a situation where we want to have 2 t1's going to another
office.
>We
> > want these 2 t1's to not
> > only provide redundancy in case 1 goes down, but also want them to
load
> > balance while they are both up.
> > So basically, we want the two t1's to be up providing 3 mpbs of
bandwidth
> > and if one goes down for it
> > to automatically send all traffic to the t1 that is still up. We
have
3600
> > series routers on both ends. Can
> > this be done? If so, please explain how. I looked into the
Multilink PPP
> > stuff, but it seems to be only for
> > async ports. Thanks for any info in advance!
> >
> >
> > _________________________________
> > FAQ, list archives, and subscription info:
>http://www.groupstudy.com/list/cisco.html
> > Report misconduct and Nondisclosure violations to
[EMAIL PROTECTED]
> >
>
>
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