From: Scott Morris (smorris@xxxxxxxxxxxxxx)
Date: Wed Aug 08 2001 - 12:42:12 GMT-3
I know the lab isn't about best practices! Sometimes real life isn't
either... But the original question came from CertificationZone, which
would use it as prep for the CCIE written. Or even for a recert exam for
that matter. Either way, written exams created by Cisco, that's the mindset
to use.
I would agree with you about the LSAs and all... But in the event of a
meshed frame network... With a scenario like that, when one office loses
it's PVC back to HQ, it therefore loses it's connection with Area 0. What
happens? (no I haven't tried it)
Just a thought.
Scott
-----Original Message-----
From: Michael Snyder [mailto:msnyder@ldd.net]
Sent: Wednesday, August 08, 2001 11:06 AM
To: ccielab@groupstudy.com; smorris@mentortech.com
Subject: Re: Two areas don't make an ABR? How about area 0 only on
loopback?
First Off, <smile> The lab isn't about best practices, dlsw comes to mind .
Running a gre tunnel over vpn also. Think of the overhead.
On the second, companies grow. Surprised you didn't catch the assigning a
new area per branch office. That's a lot of areas. I believe I can defend
that. Because as the company grows, the small branch offices become
regional offices. While I would like all pvc's to come back to the HQ, in
practice if a new branch office is within 100 miles of a regional office
most of the time the pvc terminates at the regional office. Which is fine
because the whole leg is under one ospf area set up years before.
About the third, The single hq router is the core wan. The core LAN is area
1. All subnets, web farms, etc at the hq is in area 1.
Why extend area zero to the branch offices? Think of all the LSA's you can
save by not doing so. On each leg I want only IA LSA's from the Core. In
other words, begin the leg that goes downstream as soon as possible.
Anybody see any major flaws with my thinking?
I think I can defend even more growth with this design. Say you add backup
Core router on the east coast. So you end up with:
A 7500 at the Primary HQ on the West Coast, A 7500 at the Secondary HQ (IT
wise anyway) on the east cost. All major offices have two PVC's, one east,
one west and one ospf area they are in. This limits the number of major
offices to the max number ospf areas a core router can support. Picking a
number out the air, I would use max areas=40. Then again how many companies
do you know that have 40 major offices?
You connect the two 7500's with a fat pipe cross country. The only area
zero interfaces I would use is, the loopback of the Core router one and Core
router two, and the fat pipe connecting them. The branch offices see
backbone routers either way (west or east), and the network legs still start
as soon as possible saving LSA traffic and branch office router memory and
cpu.
Getting back the question about is a router with area 0 on loopback and
single area X on a physical interface a ABR?
----- Original Message -----
From: "Scott Morris" <smorris@mentortech.com>
To: "'Michael Snyder'" <msnyder@ldd.net>
Sent: Wednesday, August 08, 2001 9:18 AM
Subject: RE: Two areas don't make an ABR? How about area 0 only on loopback?
> Interesting scenario... however, my argument for the exam would be that
it
> doesn't follow the "best practices" as lined out by Cisco, therefore it
> would be incorrect. Real life is different, however, and I follow the
> logic! However... If your company is that small, why are you running
OSPF
> versus EIGRP? Or if you're doing OSPF for the multi-vendor thing, why
> aren't all routers in Area 0 for the core WAN, and have other areas for
the
> LANs?
>
> Design issue. :)
>
> -----Original Message-----
> From: Michael Snyder [mailto:msnyder@ldd.net]
> Sent: Wednesday, August 08, 2001 9:58 AM
> To: ccielab@groupstudy.com; Scott Morris
> Subject: Re: Two areas don't make an ABR? How about area 0 only on
> loopback?
>
>
> Ok.
>
> Try this one. I do this all the time in my pod.
>
> I setup an OSPF router, with area 0 only on the loopback address. Why?
well
> on a head end, that is a single point of failure anyway, placing just one
> interface in area zero allows all the other areas and interfaces on that
> router to be very flexible. Pick a new area per subinterface per branch
> office.
>
> Think midsized company with only one core router and branch offices
hanging
> off of it.
>
> If I put area 0 only the loopback,
>
> Is this backbone router? I say yes.
> Is this ASBR router? Could be if I'm also running another protocol.
> Is this a ABR? About about if I only have one branch office? Is it still
a
> ABR?
>
>
>
>
> ----- Original Message -----
> From: "Scott Morris" <smorris@mentortech.com>
> To: "'Chuck Church'" <cchurch@MAGNACOM.com>; "'Chuck Larrieu'"
> <chuck@cl.cncdsl.com>; <ccielab@groupstudy.com>
> Sent: Wednesday, August 08, 2001 6:49 AM
> Subject: RE: Two areas don't make an ABR?
>
>
> > After reading a bunch of responses here, I'll belabor the obvious by
> > pointing out that we need to look at the entirety of the commands. :)
> >
> > Try putting them in a router EXACTLY as they are listed right there.
> > The masks on the network statements overlap for one, but also don't
> indicate
> > what's on the interface...
> >
> > If you enter answer C, you get:
> > 3620-3(config-router)#network 10.0.0.1 0.0.0.0 area 0.0.0.0
> > 3620-3(config-router)#network 192.168.1.1 0.0.255.255 area 0.0.0.1
> > 3620-3(config-router)#network 192.168.0.1 0.0.0.0 area 0.0.0.0
> > 3620-3(config-router)#
> > % OSPF: "network 192.168.0.1 0.0.0.0 area 0.0.0.0" is ignored. It is a
> > subset of a previous entry.
> >
> > So, YES, it makes it "sorta" an ABR since you have two areas. But it
> treats
> > BOTH ethernets (your REAL networks) as being part of the same area. So
> for
> > all intents and purposes in the real world, you are not an ABR!!!
> >
> > Never overlook the details. The small things will kill ya!
> >
> > Scott
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > Chuck Church
> > Sent: Wednesday, August 08, 2001 12:18 AM
> > To: 'Chuck Larrieu'; ccielab@groupstudy.com
> > Subject: RE: Two areas don't make an ABR?
> >
> >
> > What order are they evaluated in then? I was assuming top down, so the
> > first statement would put the loopback interface into area 0. The
second
> > statement would match both other interfaces, putting them in area 1.
> >
> > Chuck
> >
> > -----Original Message-----
> > From: Chuck Larrieu [mailto:chuck@cl.cncdsl.com]
> > Sent: Tuesday, August 07, 2001 11:11 PM
> > To: Chuck Church; ccielab@groupstudy.com
> > Subject: RE: Two areas don't make an ABR?
> >
> >
> > the interfaces are placed into areas based on the order of the network
> > statements. once a match is made ( just like access-lists ) the
processing
> > stops.
> >
> > answer C 192.168.1.1 0.0.255.255 area 0.0.0.1 places both interfaces
into
> > area 1. processing stops. nothing ends up in area 0. therefor the router
> is
> > not an ABR. QED
> >
> > Chuck
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > Chuck Church
> > Sent: Tuesday, August 07, 2001 7:21 PM
> > To: 'ccielab@groupstudy.com'
> > Subject: Two areas don't make an ABR?
> >
> >
> > Gang,
> >
> > Got this email today from Certification Zone. I'm not quite sure I
> > agree with the answer. Why doesn't answer 'C' meet the requirement?
> >
> > Chuck
> >
> > P.S. I don't have a Certification Zone subscription, otherwise I'd go
read
> > Howard's explanation!
> >
> >
> > 7) This Week's CCIE Challenge Question
> > ==============================================
> > Which OSPF configuration fragment will cause abr1 to function as an
> > area border router?
> >
> > hostname abr1
> > int loop0
> > ip addr 10.0.0.1 255.255.255.248
> > int e0
> > ip addr 192.168.0.1 255.255.255.0
> > int e1
> > ip addr 192.168.1.1 255.255.255.0
> >
> > a) router ospf 1
> > network 192.168.0.0 0.0.0.0 area 0.0.0.0
> > network 192.168.1.0 0.0.0.0 area 0.0.0.1
> >
> > b) router ospf 1
> > network 192.168.1.1 0.0.255.255 area 0.0.0.1
> > network 192.168.0.1 0.0.0.0 area 0.0.0.0
> >
> > c) router ospf 1
> > network 10.0.0.1 0.0.0.0 area 0.0.0.0
> > network 192.168.1.1 0.0.255.255 area 0.0.0.1
> > network 192.168.0.1 0.0.0.0 area 0.0.0.0
> >
> > d) router ospf 1
> > network 10.0.0.1 0.0.0.0 area 0.0.0.0
> > network 192.168.1.1 0.0.0.0 area 0.0.0.1
> > network 192.168.0.1 0.0.0.0 area 0.0.0.0
> >
> >
> > The answer to this week's question can be found at:
> > http://www.CertificationZone.com/QOW/1/ES/ccie-a.html
> >
> >
> > Chuck Church
> > CCNP, CCDP, MCNE, MCSE
> > Sr. Network Engineer
> > Magnacom Technologies
> > 140 N. Rt. 303
> >
> > Valley Cottage, NY 10989
> > 845-267-4000 x218
> > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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