Re: ISIS L1 vs L2

Oh - I'm not talking to you, but I had the pleasure to meet plenty of
architects ;-)

--
Marko Milivojevic - CCIE #18427 (SP R&S)
Senior CCIE Instructor - IPexpert
On Wed, Nov 28, 2012 at 11:02 AM, Ronnie Angello
<ronnie.angello_at_gmail.com> wrote:
> I'm with you, bro.  I got the CCIE first, so I definitely agree with you
> 1000%.  Didn't you see the ;) ?
>
>
> On Wed, Nov 28, 2012 at 1:44 PM, Marko Milivojevic <markom_at_ipexpert.com>
> wrote:
>>
>> 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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