Based on chuck's diagram and the use of the "E1" ospf route I think this would be a matter of how the enterprise is designed and what type of links interconnect the various locations/sites. Simply using the "DIO" metric-type could allow for suboptimal routing as chuck noted.
I realize that I was thinking that the enterprise should have dual default routes out to the ISP, when in fact by using the "E1" as howard pointed out, would allow each site to default to the nearest gateway based on the sum of the internal+external calculated by the E1 metric. So based on a well designed enterprise this would account for the individual traffic flows of each location/site to be balanced between the two ISP POPs. Wow.. this stuff is actually begining to make sense.. :-> Nigel >Reply-To: "Chuck" >To: [EMAIL PROTECTED] >Subject: Re: (correction) Method and Process Scenario 5: OSPF [7:42139] >Date: Sun, 21 Apr 2002 21:57:36 -0400 > >I think I see what you are getting to, Howard, but for the purpose of your >scenario, are you assuming that the enterprise backbone construction makes >sense? > >for example, in your case, are you assuming something like >Seattle---Portland----SanFran---SanJose---LosAngeles---SanDiego with the ISP >connections in SanDiego and Seattle, or better yet Portland and LosAngeles? > >What I'm seeing no matter how I try to construct this is that, for example, >half of Seattle's traffic traverses the entire network to get to the >LosAngeles egress while at the same time, half of SanDiego's traffic is >going past LosAngeles, and up to Portland. > >Maybe I'm digressing. Maybe this isn't necessarily a good design. OTOH, it >is a design that saves the company money due to the various pricing issues >involved, no matter what the transport decision. ( interstate, inter-lata, >inter-telco, etc ) > >tell me if I am off topic with regard to your puzzle. > >Chuck > > >""Howard C. Berkowitz"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > >question embedded within: > > > > > > > > >""Howard C. Berkowitz"" wrote in message > > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > >> >Howard, > > > > > I think I see where you're going. The default on the "DIO" > > >> >command is > > >> >applying an "E2" to the default as it is sent into the enterprise. >It > > is > > >> >also > > >> >known that by order of preference that "E2" routes are least >preffered. > > >> >So based > > >> >on your hint.. I'm thinking making use of the "metric-type" parameter >to > > >> >make > > >> >the default-route an "E1" metric which would provide known route info > > >> >into the > > >> >ISP's network. Nope..this isn't it. > > >> > > >> STOP! Using E1 is the answer, although I don't think you have the > > >> reason quite right. On the default-information originate command, > > >> use metric-type 1 and an equal metric on both routers. > > >> > > > > E1 considers the combined internal and external metric. If you make > > >> the external metrics equal, traffic in your network will go to the > > >> closest exit. If the network topology is reasonably well designed > > >> with the placement of your gateways, this should give approximate > > >> sharing of both internal resources and the ISP links. > > > > > >hhhmmmmm......... > > > > > >I'm wondering how many readers of this thread fooled themselves by >thinking > > >that the idea was to ensure per packet load sharing out the two ISP >links? > > >which no doubt leads to suboptimal routing for a significant portion of > > >traffic, if my mental picture is correct. > > > > > >aren't the two goals - equal load sharing and optimal routing - mutually > > >exclusive here? > > > > In practice, no, if you think carefully where you place the ISP > > gateways. Typically, they should be at opposite geographical ends of > > your network, near heavy concentrations of users. That often causes > > load sharing by pure use distribution. It's certainly not per-packet > > between multiple routers. It's more per-destination for individual > > routers, CEF of course giving even better results than fast switching. > > > > The optimal routing to which we are referring is internal, not > > external. It presupposes the ISP links are of equal capacity. > > > > >Message Posted at: >http://www.groupstudy.com/form/read.php?f=7&i=42192&t=42139 >-------------------------------------------------- >FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ------------------------------------------------------------------------ MSN Photos is the easiest way to share and print your photos: Click Here Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=42196&t=42139 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
