Re: ISIS L1 vs L2

But you are. Like the example in this thread. Choosing flat L1/L2
instead of flat L2 would double the memory requirements for IS-IS
alone. It's an issue of scale and that is one of the fundamentals in
the network design.

I *firmly* believe that network designer/architect must have 100%
grasp of bit-level issues. Not necessarily the configuration, but how
protocols work, operate, interoperate, etc. is an absolute
prerequisite to be a good network designer/architect.

--
Marko Milivojevic - CCIE #18427 (SP R&S)
Senior CCIE Instructor - IPexpert
On Wed, Nov 28, 2012 at 10:30 AM, Ronnie Angello
<ronnie.angello_at_gmail.com> wrote:
> Yeah, I have to agree.  I actually went to the CP site to download the
> errata, and didn't even find what I was looking for.  I recall some shaky
> stuff around OSPF stub area types and what LSA types are allowed/not
> allowed.  Found some other stuff that I don't recall...  Also agree that
> it's the best routing design book that I've read.  There are some good ones
> out there that are focused on individual routing protocols or technologies,
> but this is the best when it comes to general L3 network design.
>
> While you have to verify all technical content, the pieces that I find
> particularly good - general routed design theory, topology design theory,
> tunneling technologies and interaction with routing, fast convergence, down
> detection, etc.  The bit/byte level detail stuff needs some review/cleaning
> up as you've pointed out, but then again us CCDEs aren't supposed to care
> about that.  :)
>
> Ronnie
>
>
> On Wed, Nov 28, 2012 at 1:06 PM, Marko Milivojevic <markom_at_ipexpert.com>
> wrote:
>>
>> ~sigh~ since you bring ORD again, I will now write what I deleted earlier.
>>
>> It's a truly terrible book. I read it 3-4 times and apart from blatant
>> erros, there are MANY things in there that make no sense. The problem
>> is - it's still probably the best overall routing design book from
>> Cisco Press. There are others, more focused ones (like Definitive MPLS
>> Network Designs), but it's shocking how this book passed the technical
>> review. I suppose everyone reviewing was in awe of the author(s).
>>
>> --
>> Marko Milivojevic - CCIE #18427 (SP R&S)
>> Senior CCIE Instructor - IPexpert
>>
>> On Wed, Nov 28, 2012 at 10:02 AM, Ronnie Angello
>> <ronnie.angello_at_gmail.com> wrote:
>> > LOL yeah, he was talking about that one before.  That's one of his
>> > titles that I haven't bought...  Looks like price isn't an issue though!
>> >
>> > So CCDE tip of the day... always ask why!  I blindly followed ORD today
>> > (probably because I've read it like 8 times) and got bit...  Don't accept
>> > the stuff in books or case studies as is.  Ask why...
>> >
>> > Ronnie
>> >
>> > Sent from my iPhone
>> >
>> > On Nov 28, 2012, at 12:54 PM, Brian McGahan <bmcgahan_at_ine.com> wrote:
>> >
>> >> Speaking of CCDE and Optimal Routing Design, INE had a CCDE study
>> >> session last week and I was showing people recommended books to go through
>> >> on Amazon.  I was going through the list of books that Russ White wrote and
>> >> I came across this gem:
>> >>
>> >> Loss of Carrier [Paperback]
>> >> Russ White (Author)
>> >>
>> >> Jess Wirth lives a dreary life. He spends most of his time crammed
>> >> inside a cubicle, toiling as a network engineer and stewing over the details
>> >> of his ugly divorce. But when he finds his co-worker dead in the basement of
>> >> their office, Jess's life takes a surprising-and unpleasant-turn. The police
>> >> quickly declare the death a suicide, but Jess isn't so sure. Not long after
>> >> he begins digging into the victim's work, another co-worker turns up dead,
>> >> convincing him once and for all that something sinister is brewing behind
>> >> the cubicle walls. His investigation leads him to a mysterious woman name
>> >> Leah, who pushes him to entrust her with the information he's collected
>> >> about his dead colleagues. Wary of Leah's motives yet inexorably drawn to
>> >> her, Jess keeps her at arm's length...until an attempt is made on both their
>> >> lives. Realizing they are close on the trail of a dangerous criminal, the
>> >> pair race to expose a data theft ring before they become the killer's next
>> >> victims.
>> >>
>> >>
>> >> It's a networking murder mystery by Russ White :)  Kindle edition is
>> >> only $1.99. This is totally on my reading list now ;)
>> >>
>> >> Brian
>> >>
>> >>
>> >>
>> >> -----Original Message-----
>> >> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>> >> Brian McGahan
>> >> Sent: Wednesday, November 28, 2012 11:48 AM
>> >> To: Ronnie Angello
>> >> Cc: shiran guez; Routing Freak; Cisco certification
>> >> Subject: RE: ISIS L1 vs L2
>> >>
>> >> The best part being the drunker we became the louder we became, and the
>> >> louder person is always right by default ;)
>> >>
>> >>
>> >>
>> >> From: Ronnie Angello [mailto:ronnie.angello_at_gmail.com]
>> >> Sent: Wednesday, November 28, 2012 11:22 AM
>> >> To: Brian McGahan
>> >> Cc: shiran guez; Routing Freak; Cisco certification
>> >> Subject: Re: ISIS L1 vs L2
>> >>
>> >> Reminds me of the drunken OSPF vs IS-IS discussion in Chicago after
>> >> CCDE.  Remember that?  ;)
>> >>
>> >> Sent from my iPhone
>> >>
>> >> On Nov 28, 2012, at 10:48 AM, Brian McGahan
>> >> <bmcgahan_at_ine.com<mailto:bmcgahan_at_ine.com>> wrote:
>> >> If youb re not going to grow to other areas then it doesnb t matter;
>> >> flat L1 everywhere is the same as flat L2 everywhere.  For example think of
>> >> it within the scope of OSPF.  If you have an OSPF network that is area 0
>> >> everywhere vs. a network that is area 1 everywhere, they will both have the
>> >> same operational behavior.  All routers and links are in the same flooding
>> >> domain and failure domain.  The problem comes in if you want to grow the
>> >> network to other areas.  With OSPF flat area 1 wonb t work because you canb
>> >> t add other non-area 0 areas.  The same is true with IS-IS.
>> >>
>> >> Most flat IS-IS networks use L2 everywhere, just in case there is a
>> >> need to add hierarchy later.  But like I said if youb re never going to add
>> >> hierarchy in the future it doesnb t matter, just with L2 everywhere you have
>> >> that option down the road without having to do a major redesign.
>> >>
>> >> The only thing you want to make sure *not* to do is to run L1 and L2 on
>> >> all links.  This would be the same as running both OSPF area 0 and area 1 on
>> >> all links, or running two separate OSPF processes that are enabled on all
>> >> links.  The only thing L1 and L2 will do for you if you run it everywhere is
>> >> to increase the amount of memory and CPU resources that your routers need,
>> >> and potentially add to your convergence time when a failure event occurs.
>> >>
>> >> You may want to check out the book b OSPF and IS-IS: Choosing an IGP
>> >> for Large-Scale Networksb  by Jeff Doyle for more info on the comparison of
>> >> the two.
>> >>
>> >>
>> >> HTH,
>> >>
>> >> Brian McGahan, CCIE #8593 (R&S/SP/Security)
>> >> bmcgahan_at_INE.com<mailto:bmcgahan_at_INE.com>
>> >>
>> >> Internetwork Expert, Inc.
>> >> http://www.INE.com
>> >>
>> >>
>> >>
>> >> From: Ronnie Angello [mailto:ronnie.angello_at_gmail.com]
>> >> Sent: Wednesday, November 28, 2012 9:34 AM
>> >> To: shiran guez
>> >> Cc: Routing Freak; Cisco certification; Brian McGahan; Narbik
>> >> Kocharians; Marko Milivojevic; Brian Dennis
>> >> Subject: Re: ISIS L1 vs L2
>> >>
>> >> So at least we agree don't do L1 only...  I honestly haven't done much
>> >> real world IS-IS design, but my reference is Optimal Routing Design (Chapter
>> >> 5, page 190).
>> >>
>> >> Ronnie
>> >>
>> >> Sent from my iPhone
>> >>
>> >> On Nov 28, 2012, at 9:56 AM, shiran guez
>> >> <shiranp3_at_gmail.com<mailto:shiranp3_at_gmail.com>> wrote:
>> >> L1/L2 everywhere is not making much sense as you will have redundant
>> >> database for both L1 and L2. normally Core you will work L2 edge to "stub"
>> >> you will do L1/L2 and stub networks you will set L1, L2 will provide you
>> >> future flexibility, even if you think that you will not expand or change, it
>> >> is not a good design to do a limit yourself from the start, it does not cost
>> >> anything to do it L2, but it will cost plenty if you will need to change
>> >> Core in future.
>> >>
>> >> my 2 cents :-)
>> >>
>> >> On Wed, Nov 28, 2012 at 3:18 PM, Ronnie Angello
>> >> <ronnie.angello_at_gmail.com<mailto:ronnie.angello_at_gmail.com>> wrote:
>> >> A single L1/L2 domain would be best as it provides flexibility...  That
>> >> way you already have a contiguous L2 domain.  If the network grows, it's
>> >> easier to add an L1 routing domain than it is to add an L2 routing domain.
>> >> You just add an L1 IS to the edge and push the L1 domain into the network...
>> >>
>> >> Ronnie
>> >>
>> >> Sent from my iPhone
>> >>
>> >> On Nov 27, 2012, at 10:24 PM, Routing Freak
>> >> <routingfreak_at_gmail.com<mailto:routingfreak_at_gmail.com>> wrote:
>> >>
>> >>> Hi all
>> >>>
>> >>> In my customer core network where we had a heated about wither OSPF or
>> >>> ISIS and finally ISIS won the race for the core IGP due to some
>> >>> business decision and now my problem here is that when i was designing
>> >>> the network with one large ISIS area with all the linka s L1, everyone
>> >>> opposed me to not to configure L1 and go for L2.
>> >>>
>> >>> I know that L1 is within single area and L2 can be connected across
>> >>> areas and also within a single area and it carries all the routes
>> >>> within L1 and L2.
>> >>>
>> >>> But in my design , i have single large area with all links as L1, what
>> >>> is the problem in that, L1 or L2 it should be the same.
>> >>>
>> >>> I didnt understood what is the logic behind the fact that L1 should
>> >>> not be used and L2 should be used.
>> >>>
>> >>> I thought may be when they are forming more areas, then l2 makes
>> >>> sense, but they r not going to expand the site with another area, so
>> >>> why not going for
>> >>> L1 will suffice the requirement .
>> >>>
>> >>> L1 is within one single area and doesnt know any other routes of other
>> >>> area
>> >>>
>> >>> L2 router is one where all the areas merge and exchange routes in one
>> >>> separate area. It can be any area and not area 0 and just all the
>> >>> routers in that particular area should be running L2 adjacency with
>> >>> each other.
>> >>>
>> >>>
>> >>> In one large area, which is better L1 or L2. Any ISIS Experts, be sure
>> >>> to reply to this.
>> >>>
>> >>>
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>> >>>
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>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> --
>> >> Shiran Guez
>> >> MCSE CCNP NCE1 JNCIA-ENT JNCIS-ENT CCIE #20572
>> >> http://cciep3.blogspot.com
>> >> http://www.linkedin.com/in/cciep3
>> >> http://twitter.com/cciep3
>> >>
>> >>
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>> >>
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