From: Peter Van Oene (pvo@xxxxxxxxxxxx)
Date: Thu Aug 09 2001 - 22:23:33 GMT-3
Couple thoughts. First off, OSPF strictly enforces hierarchy and thus there is
no option to create a topology without it. You simply have non backbone areas
connected to a backbone area. This hierarchy is a loop prevention mechanism t
hat, along with some split horizon like functionality used in route computation
, helps solve the traditional distance vector oriented problems that OSPF has i
n inter area routing. I fully agree that with you about the 50 being a generic
rule however and stand by my original point that area sizing has everything to
do with router horsepower. I think we've covered the fact that the size depen
ds on things like link stability, number of prefixes (internal/external), numbe
r of areas on ABR's etc etc.
In most cases, in growing networks I think other scalability limits beyond the
number of routers will dictate how and when to segment the network. Having too
many Type 5's that add little value to groups of routers may justify segmentin
g those groups and creating stub areas. Having too many specific prefixes may
create the need for aggregation to minimize routing table sizes.
Anyway, I think the point that area size depends on a plethora of issues has be
en well stated :)
Pete
*********** REPLY SEPARATOR ***********
On 8/9/2001 at 9:16 AM Matt Wagner wrote:
>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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