From: Joseph D. Phillips (josephdphillips@fastmail.us)
Date: Thu Jul 15 2004 - 15:54:45 GMT-3
Wow, that's great!
On Thu, 15 Jul 2004 14:37:41 -0400, "Howard C. Berkowitz"
<hcb@gettcomm.com> said:
> At 9:58 AM -0700 7/15/04, Joseph D. Phillips wrote:
> >There are many political or economic reasons why optimal routing isn't
> >always possible or desired.
> >
> >The job of a network engineer, as I see it, is to ensure data flows
> >according to the requirements and directives of the organization. You
> >may have great ideas about how to improve the flow of traffic, but you
> >can slam into bureaucratic walls trying to implement your designs.
> >
> >Can I get a witness? Scott? Brians? Howard?
>
> Thanks -- I've been meaning to respond.
>
> Optimal routing has no single meaning. For example, there is the
> concept variously called hot potato or closest exit routing. Examples
> here would be an ISP handing off the packet to the first exit it can
> find, so the workload imposed on the ISP backbone is minimized.
>
> In like manner, in an OSPF totally stubby area with multiple ABRs,
> you only have information to get the packet to the closest ABR -- you
> are only locally optimizing within the area. Broadening the scope of
> OSPF to ISPs, you can use Type 1 externals to load share within your
> domain, but, without traffic engineering, you have no control of
> optimization once the packet leaves your domain.
>
> It's been my experience that people tend to overemphasize routing by
> metric, etc., in that there usually aren't so many different possible
> routes that the best metric really makes much different. Topology,
> particularly hierarchical topology, tends to be far more important.
>
> I'm working on some practice labs in which I consciously have a
> section called "the right way, the wrong way, and the Cisco way." In
> the one I'm testing at the moment, the basic solution will tend to
> put traffic over a 64 Kbps link known to OSPF, rather than a 10 Mbps
> link known to Ethernet. I have a specific last step that plays games
> with redistribution metrics and distances to force the traffic onto
> the "best" path. It is my impression that Cisco would not ask for
> such in the CCIE lab, and I'm trying to emphasize the difference --
> trying to tell people when something is good enough for the lab
> requirmeents.
>
> >
> >
> >
> >
> >
> >----- Original message -----
> >From: "Kenneth Wygand" <KWygand@customonline.com>
> >To: "Kenneth Wygand" <KWygand@customonline.com>, ccielab@groupstudy.com
> >Date: Thu, 15 Jul 2004 12:40:30 -0400
> >Subject: Re: Suboptimal Routing?
> >
> >Surely someone has an opinion on this or can explain why this is (or
> >should be) done.
> >
> >Thanks in advance,
> >Ken
> >--------------------------
> >Sent from my BlackBerry Wireless Handheld
> >
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com <nobody@groupstudy.com>
> >To: ccielab@groupstudy.com <ccielab@groupstudy.com>
> >Sent: Wed Jul 14 20:57:34 2004
> >Subject: Suboptimal Routing?
> >
> >I have a generic question regarding suboptimal routing on the CCIE lab.
> >
> >Suppose I have both RIP and OSPF running in my network. I have two
> >routers that are running both RIP and OSPF (on the RIP/OSPF border).
> >One of these routers is mutually redistributing RIP and OSPF (let's call
> >this "Router 1"). Without changing distances or filtering, routes that
> >originate in RIP and are redistributed by "Router 1" into OSPF will be
> >received by "Router 2" in OSPF. So now Router 2 will know of routes
> >from the RIP domain through both it's own RIP routes and also through
> >the OSPF routes. Of course, the distance of OSPF is less than RIP, so
> >it will default to choose the routes that "go all the way around the
> >world" to get back into the RIP domain.
> >
> >This is a clear case of "suboptimal routing" but still provides full IP
> >connectivity. Every single practice lab I've ever come across has
> >always "treated" this situation by using some mechanism (filtering,
> >distance, etc) to cause the native RIP routes to be preferred through
> >RIP as opposed to the "all the way around the world" OSPF routes.
> >
> >However, none of these labs ever say "ensure you avoid suboptimal
> >routing". I've also heard many times that the lab is "not testing
> >real-world best practices, only that you meet the requirements of the
> >question". Well, if the question states I must have IP reachability,
> >then why should I bother fixing suboptimal routing. Sure, it will
> >display to the proctor that I understand it and I know what I'm doing,
> >but why -specifically- do I have to do it to get points on my exam? If
> >it doesn't say to avoid this, why should I waste my time?
> >
> >Thanks in advance, as I really look forward to your responses.
> >Ken
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Sun Aug 01 2004 - 10:11:56 GMT-3