On Fri, 20 Apr 2001, [EMAIL PROTECTED] wrote:
> [ElephantChild wrote:]
>
> [You want to load-balance 30% (100% - 70% load threshold needed for ISDN to
> kick in) of your T1's bandwidth, which is about 450 Kbits/sec., with 1 ISDN
> channel, which will give you 1/7 at best of that bandwidth.]
>
> I am not sure I understand what you are saying?
>
> Isn't the "BACKUP LOAD {enable-threshold | NEVER} {disable-threshold |
> NEVER}" command specifying when the backup interface will be kicked in, and
> dropped? It has been a while but looking through the docs again it seems
> that the BRI will kick in at 70% util (input or output 5 minute moving
> average). It will remain up until the COMBINED utilization of the two
> (input or output 5 minute moving average) drops bellow 30% of the S1/0
> bandwidth.
It is. The BRI kicks in at 70% of the T1's bandwidth, so the fraction of
the T1's bandwidth that gets spread out is the remaining 30%, or perhaps
the difference between 70% and the peak usage, come to think of it. If
the original poster didn't baseline that already, now would be a good
time to.
> I donn't see how the backup delay really has anything to do with the
> "loadsharing" issue?
It doesn't, but I never said it did. :-) The 30% I mentioned comes from
100% (full T1 bandwidth) - the 70 of the backup load command, not the 30
of the backup delay.
> As I write this I find that I have some questions?
> ### It has been a while, and the Docs are a little vague###
> 1. Can either the input or output utilization start the backup?
> 2. Once the backup is enabled do BOTH the input and output utilizations
have
> to be bellow the disable-threshold to drop the backup.
I don't have routers handy to experiment on, but my guesses would be:
1. No. Backup requires that the ISDN or analog line be setup to call the
same router as the point-to-point line it's supposed to back up,
IIRC. Hence, the output load on one router should be the same as the
input load on the other.
2. Dunno either. It would make sense for it to, since otherwise the
other router would restart the backup at once. OTOH, it assumes that
both have the same backup load thresholds.
Perhaps someone would care to set up a lab and report? Chuck?
Circusnuts? Cthulu? Anyone? :-)
> "ElephantChild" wrote:
> >
> > On Thu, 19 Apr 2001, Paul L Holloway wrote:
> >
> > > I have a customer wanting his ISDN line(BRI)to take up the slack when
the
> > > utilization on his T1 gets to high. He has a 3640 router. I know the
load
> > > balancing considerations for routing protocols and am suggesting he run
> > > EIGRP as his IGP since OSPF won't load balance across two "unequal"
> paths.
> > > The config. on his serial I believe would be:
> > >
> > > int S1/0
> > > ip address x.x.x.x x.x.x.x
> > > no ip redirects
> > > no ip directed-broadcast
> > > no ip proxy-arp
> > > encapsulation ppp
> > > no ip route-cache distributed
> > > no fair-queue
> > > no cdp enable
> > > backup delay 30 60
> > > backup int BRI1/0
> > > backup load 70 40
> > >
> > > Are there any other snags or problems I may run into with this setup?
> > > Thanks in advance.
> >
> > Hmm, you configured it as a serial interface, wo I assume that the whole
> > bandwidth of your T1 goes to a single destination (eg, ISP router port).
> > You want to load-balance 30% (100% - 70% load threshold needed for ISDN
> > to kick in) of your T1's bandwidth, which is about 450 Kbits/sec., with
> > 1 ISDN channel, which will give you 1/7 at best of that bandwidth.
> >
> > So the main snag, I would think, is that your ISDN won't help that much.
> > OTOH, it will come handy when your T1 gets acquainted with a backhoe,
> > which also appears to be one of your design goals, since you put in a
> > backup delay. Depending on how you rank these design goals, you'll get a
> > satisfied customer or an irate one.
--
"Someone approached me and asked me to teach a javascript course. I was
about to decline, saying that my complete ignorance of the subject made
me unsuitable, then I thought again, that maybe it doesn't, as driving
people away from it is a desirable outcome." --Me
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