From: ccie2be (ccie2be@nyc.rr.com)
Date: Fri Nov 07 2003 - 15:13:59 GMT-3
My bad, I probably clicked the wrong button - reply instead of reply all.
That CertificationZone looks like it will be very helpful. I'm going to
sign up.
Thanks, dt
----- Original Message -----
From: "Howard C. Berkowitz" <hcb@gettcomm.com>
To: "ccie2be" <ccie2be@nyc.rr.com>
Sent: Friday, November 07, 2003 12:37 PM
Subject: Re: Relative Importance of ISIS (Metric-style command)
> >Hi Howard,
> >
> >Thanks for getting back to me. I'm especially impressed that among all
the
> >folks on GS, you would take the time to respond to my post. (It's been
> >rumored that you're one of the top internetworking guru's out there even
> >though you don't have a ccie. I've heard that you're involved in writing
> >those RFC's that end up being implemented by various vendors.)
> >
> >So, you're thinking of creating a ISIS study aid? How do I sign up to
get
> >one of the first copies? Given the leaky bucket that passes as my brain,
I
> >need all the study aids I can get.
>
> There's a two-part ISIS guide, written by Peter van Oene, at
> Certificationzone.com, as well as multipart OSPF and BGP guides I
> wrote. The comparison chart is something I expect to write in the
> next month or so.
>
> >
> >On a more serious note, I'm trying to better understand how to know when
I
> >need to change the metric style from it's default, narrow, to wide.
>
> See Abe Martey's _ISIS Network Design Solutions_ (Cisco Press), p
> 173-4, p 222-225.
>
> Now that this is said, I have to make a timeout signal. When I
> discuss this sort of thing with the community at large, I make a
> point of doing it on the Groupstudy list, so others can benefit and
> others can contribute. Priscilla has the same philosophy, and goes
> further than I do in using a posting-only email address. Peter knows
> ISIS better than I do, and might have other insights.
>
> More than anything, it's a scalability issue. If I allow myself to
> get into individual discussions with lots of people, outside the
> context of a contract or something like the IETF, I start running out
> of time to do billable things -- not that I have as much of that as
> I'd like. The economy sucks everywhere.
>
> >I've
> >looked at the command reference but it didn't answer that question except
to
> >say it's needed when doing MPLS traffic engineering. Does that mean, if
> >MPLS isn't running, the metric style can always be left at it's default
> >value? Also, do all ISIS routers in a network have to run the same
metric
> >style for networking to work properly? Lastly, if I'm not running the
right
> >metric style, how would I know? What would the symptoms look like?
> >
>
>http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/swt
ch_r/swi_m1.htm#1060108
> >
> >As a side note, why doesn't the command show up in the 12.2 command
> >reference even though it was introduced in 12.0?
>
> Cisco moves in mysterious ways.
>
> >
> >12.2 ISIS command reference:
> >
>
>http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fip
rrp_r/1rfisis.htm
> >
> >thanks again for getting back to me. dt
> >
> >
> >----- Original Message -----
> >From: "Howard C. Berkowitz" <hcb@gettcomm.com>
> >To: <ccielab@groupstudy.com>
> >Sent: Friday, November 07, 2003 10:05 AM
> >Subject: Re: Relative Importance of ISIS
> >
> >
> >> At 8:41 AM -0500 11/7/03, ccie2be wrote:
> >> >Hi group,
> >> >
> >> >I'm trying to decide how much time to spend on IS-IS. I understand
the
> >basics
> >> >and can configure level I and II areas and can set up a simple multi
area
> >ISIS
> >> >network, but I'm weak on all the more advanced stuff. I have only a
> >couple
> >> >weeks left before the lab and I also want to review and practice QoS,
> >Voice,
> >> >and ATM.
> >> >
> >> >Compared to those other 3 topics, how much time should I spend
practicing
> >> >ISIS? By way of comparison, I'm very strong on OSPF. How important
is
> >it
> >> >that I be just as strong on ISIS as I am on OSPF?
> >>
> >> Let me answer indirectly. It would enhance your understanding of
> >> both ISIS and OSPF to make a matrix of general protocol functions
> >> (e.g., neighbor establishment, database synchronization, flooding,
> >> DR/pseudonode election, etc.) and then make a matrix with a brief
> >> note on how OSPF and ISIS each do it. You'll find the protocols tend
> >> to have functions in common, but quite different detailed
> >> implementation. You might even do just a single column about how
> >> ISIS differs from OSPF (e.g., single pseudonode/DIS rather than
> >> DR/BDR, or that ISIS L1 areas are equivalent to OSPF totally stubby
> > > areas).
> >>
> >> It's a tossup whether you need to be as strong in ISIS. A lot of the
> >> complexity in ISIS deals with ISP-oriented tuning or traffic
> >> engineering. One of the reasons OSPF is preferred in enterprises is
> >> that it has a lot more policy/summarization/area options, which ISPs
> >> generally don't need. THe real question is how much you'd expect
> >> Cisco to test for ISP-oriented features, which they don't teach in
> >> their general classes, in the fundamentally enterprise-oriented
> >> CCIE/R&S.
> >>
> >> >
> >> >Also, do people think it's worthwhile to learn all the details of all
the
> >> >tuning parameters of which there seem to be many?
> >> >
> >>
> >> Funny you should mention that, because I've been working on some
> >> study material updates, and just concluded that a study aid is
> >> probably needed here.
> >>
> >> While there are probably too many timers to memorize, these are
> >> things that they love to test for. I think the first step is to
> >> think of generic protocol timer functions, such as hello/periodic
> >> update interval, processor churn protection (e.g., holddown timers in
> >> LS protocols, exponential backoff), hello and dead intervals, etc.
> >>
> >> Next, draw up a matrix and write in the equivalent command, when it
> >> exists, for each routing protocol. If you're like me, you'll wind up
> >> memorizing quite a bit by the act of writing the matrix. In high
> >> school, one of my favorite ways to prepare for a test is to write up
> >> what would be a cheat sheet, but leave it at home.
> >>
> >>
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