you're correct *only* if you're dealing with INTRA-AREA routes. Read up on
OSPF again and look at the order of precedence for OSPF route selection,
especially around routes provided by ABRs.
-e-
----- Original Message -----
From: "Hire, Ejay"
To:
Sent: Tuesday, May 29, 2001 8:09 AM
Subject: RE: Want to Be a CCIE? Try This One [7:6076]
> IIRC, OSPF works on the basis of path cost. To make the router Prefer a
> path, you
> A. Raise the cost of the bad link above the good link
> or
> B. Lower the cost of the good link below the bad link
>
> From CCO, I see that
> ---Begin quote from
> http://www.cisco.com/cpress/cc/td/cpress/design/ospf/on0407.htm
> The cost associated is determined (default) by the interface bandwidth
> statement unless otherwise configured to maximize multiple path routing.
>
> Before Cisco's IOS release 10.3, the default cost was calculated by
dividing
> 1,000,000,000 by the default bandwidth of the interface. However, with IOS
> releases after 10.3, the cost is calculated by dividing 1,000,000,000 by
the
> configured bandwidth
> ---End quote from
> http://www.cisco.com/cpress/cc/td/cpress/design/ospf/on0407.htm
>
> There are two paths from A to C.
> a-c
> a-b-d-c
>
> Since you want to prefer the a-b-d-c link in the least amount of
> configuration possible, then you would increase the cost of the a-c link.
> This can be done based on the configured bandwidth of the link, or using
the
> ospf Cost command. Example...
>
> config term
> interface serial 0/0
> description RouterAs connection from RouterA to RouterC
> Router(config-if)#ip ospf cost ?
> Cost
> Router(config-if)#ip ospf cost 65534
>
>
> Since this link has an excessively high cost, ospf should use the other
> link. You will also have to do this on Router C so that the traffic will
> take c-d-b-a as the preferred route back.
>
> BTW, if you ping RouterC's serial link, it will still go from a-c because
> it's a connected interface. If you trace a host served by routerC it
should
> go a-b-d-c.
>
> Let me know If I'm incorrect,
> Ejay Hire
>
> -----Original Message-----
> From: Kevin Schwantz [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, May 29, 2001 10:03 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Wanna Be a CCIE? Try This One [7:6076]
>
>
> routerA routerB
> AREA0--------AREA0
> | |
> routerC routerD
> AREA1---------AREA1
>
>
> Since we are on the topic of OSPF, could someone help me out on the
scenario
> above?
>
> Routers A and B have interfaces in Area 0 and Area1. I want traffic from
> routerA destined for routerD to go via router B. This is not the case in
my
> network because I realise that routerA prefers Intra-Area routes and thus
> would route traffic to routerD via routerC.
> What tweaks must I make in order to force the traffic from routerA to
> routerD to go via routerB ? Someone suggested building a GRE tunnel
between
> routerA and routerB and then configure the tunnel to be in AREA1.
>
> Any suggestions?
>
> Kevin
>
>
> ""W. Alan Robertson"" wrote in message
> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > Guys,
> >
> > The actual traffic will not be routed up to area 0... Area 0 has been
> > extended
> > down to R2, so R2 is now a backbone router. R2 has interfaces in 3
areas
> > now:
> > Area1, Area2, and Area0 by means of it's virtual link.
> >
> > Any traffic originating in Area2 destined for Area1 will be routed
> directly
> > by
> > R2. This satisfies the "Interarea traffic must traverse the backbone"
> rule,
> > because R2 *is* a backbone router.
> >
> > This is not theory... It is fact.
> >
> > Alan
> >
> > ----- Original Message -----
> > From: "Andrew Larkins"
> > To:
> > Sent: Monday, May 28, 2001 10:13 AM
> > Subject: RE: Wanna Be a CCIE? Try This One [7:6076]
> >
> >
> > > agreed....to area 0 then on to the intended area
> > >
> > > -----Original Message-----
> > > From: Circusnuts [mailto:[EMAIL PROTECTED]]
> > > Sent: 28 May 2001 15:50
> > > To: [EMAIL PROTECTED]
> > > Subject: Re: Wanna Be a CCIE? Try This One [7:6076]
> > >
> > >
> > > Chuck- my answer is Yes. The traffic from the Virtual Linked
psuedo-ABR
> > > passes back to Area 0, before it's sent onto the intended Area (even
if
> > it's
> > > directly connected).
> > >
> > > Phil
> > >
> > >
> > > ----- Original Message -----
> > > From: Chuck Larrieu
> > > To:
> > > Sent: Sunday, May 27, 2001 8:59 PM
> > > Subject: Wanna Be a CCIE? Try This One [7:6076]
> > >
> > >
> > > > Ever wonder what the CCIE candidates talk about on the CCIE list?
> > > >
> > > > The following message came through today. I thought the bright folks
> on
> > > this
> > > > list might be curious, and might want to venture an answer.
> > > >
> > > > Begin original question:
> > > >
> > > > Guys,
> > > >
> > > > I wonder if there is anybody who remembers the discussion on Virtual
> > > > Links in OSPF. It was posted some time ago but I can't seem to find
> it.
> > > >
> > > > The scenario was something like this:
> > > > ________ _______ _______
> > > > |Area 0 | |Area1| |Area2|
> > > > | R0 |--| R1 |--| R2 |
> > > > |______| |_____| |_____|
> > > >
> > > > There is a virtual link from area 2 to Area 0 via Area1. Traffic
needs
> to
> > > > get to R1 in Area 1 from R2 in Area 2. Assume that the virtual link
> has
> > to
> > > > use R1 (To create the V.Link). Does the traffic flow passed R1 (in
> Area
> > 1)
> > > > to Area 0 and then back to area 1, or does the actual flow just to
R1
> > from
> > > > R2.
> > > >
> > > > I cant remember the conclusion, and I cant seem to find it on the
> > > archives.
> > > > Quite interesting issues.
> > > >
> > > > End of original question
> > > >
> > > >
> > > > Chuck
> > > >
> > > > One IOS to forward them all.
> > > > One IOS to find them.
> > > > One IOS to summarize them all
> > > > And in the routing table bind them.
> > > >
> > > > -JRR Chambers-
> > > > FAQ, list archives, and subscription info:
> > > http://www.groupstudy.com/list/cisco.html
> > > > Report misconduct and Nondisclosure violations to
[EMAIL PROTECTED]
> > > FAQ, list archives, and subscription info:
> > > http://www.groupstudy.com/list/cisco.html
> > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
> > > FAQ, list archives, and subscription info:
> > http://www.groupstudy.com/list/cisco.html
> > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
> > FAQ, list archives, and subscription info:
> http://www.groupstudy.com/list/cisco.html
> > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
> FAQ, list archives, and subscription info:
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> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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