From: Brian Hescock (bhescock@xxxxxxxxx)
Date: Fri Aug 10 2001 - 00:06:47 GMT-3
Moy certainly knows his stuff but, if how you quote him is accurate, then
I would certain question his point of view on that particular subject.
Virtual-link is a band-aid fix for a less than perfect design and should
be avoided if possible (in my opinion). Granted, there are situations
where it may be needed in the short term for a quick fix but that's all.
Why introduce additional complexity into your network and a greater potential
source of problems and give you nightmares when troubleshooting? OSPF is
a very good routing protocol but for those of who have ever had really dig
deep into it (i.e. into the ospf database) to resolve a difficult problem
know it can be very difficult to troubleshoot. Create a good design to
begin with and don't rely on virtual links.
B.
On Thu, 9 Aug 2001, Brent D. Stewart wrote:
> I don't have any direct experience on this, but the Moy book tosses out
> numbers like 200 routers in an area. I'm familiar with the Cisco
> rule-of-thumb, so I've often wondered if it was an implementation issue or
> if Moy just picked a number.
>
> Also, Moy seems to talk about virtual-links as part of a good design that
> maintains a rigid logical structure but can "flow" to fit any network. My
> reading of the Cisco literature is that they aren't as thrilled with virtual
> links.
>
> In terms of the lab, not an issue. Good luck in your lab.
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Chuck Larrieu
> Sent: Thursday, August 09, 2001 11:44 AM
> To: Matt Wagner; ccielab@groupstudy.com
> Cc: strongbow71@gmx.at
> Subject: RE: OSPF Limits
>
>
> as with anything, the answer is "it depends"
>
> the design guide that I referred to appears to have been written more than a
> couple of years ago. the recommendations there came from extensive field
> experience with large customers, if my sources are correct.
>
> that said, yes, the mitigating factors are processor, memory, stability of
> the network links throughout the ospf domain, whether or not good design
> practice has been followed, and effective summarization is in place. the
> killer in OSPF is the running of the Djikstra algorithm, and not necessarily
> the number of routes, the number of routers, the number of links, or the
> number of areas to which a router is connected.
>
> we recently had a discussion along these lines on the regular groupstudy
> list. I walked away from that discussion questioning a couple of things that
> Cisco and the study materials preach as gospel, including the issue of
> scalability of static routing. It occurred to me that under certain designs,
> static routing / on demand routing could actually involve far less work and
> provide far greater stability than configuring any routing protocol.
>
> as with everything Cisco, "it depends"
>
> Chuck
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Matt Wagner
> Sent: Thursday, August 09, 2001 8:17 AM
> To: ccielab@groupstudy.com
> Cc: strongbow71@gmx.at
> Subject: Re: OSPF Limits
>
>
> Hey (group), let me know if I'm wrong about this, but the "50" rule is a
> generic rule. Whether you can support more or less than that depends on a
> few things, like whether you are set up entirely hierarchically or whether
> you are looping all over the place, the number of ASBRs, etc. I also am
> pretty sure that it has less to do with the horsepower of the routers you
> are using and more to do with the protocol itself handling a database with a
> certain degree of complexity well, which is the main reason you shouldn't
> redistribute BGP into OSSPF.
>
> With proper design, you can probably handle more that 50 routers, and with
> poor design, probably fewer. That's just what I have always thought,
> though. Any comments would be appreciated.
>
> Matt
>
>
> A man said to the Universe, "Sir, I exist".
> The Universe replied, "The fact may be,
> but it inspires in me no sense of obligation."
>
>
>
> ----Original Message Follows----
> From: "Dietmar Gaar" <strongbow71@gmx.at>
> Reply-To: "Dietmar Gaar" <strongbow71@gmx.at>
> To: <ccielab@groupstudy.com>
> Subject: OSPF Limits
> Date: Thu, 9 Aug 2001 11:59:12 +0200
>
> Hi,
>
> I4m playing around with OSPF last Days preparing for the Lab Exam.
>
> So in practice, when you have not a perfect but a good Design - how "big"
> can an OSPF Interwork grow up ? Exist there some practical based Limits ?
>
> I already know that there a many unknown Parameters to take a care of - but
> maybe you can give me some scales...
>
> kind regards,
>
> Dietmar
> **Please read:http://www.groupstudy.com/list/posting.html
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