From: Dinesh Patel (jedidinesh@googlemail.com)
Date: Sat Mar 08 2008 - 20:57:48 ARST
Hi,
I've set this scenario up in dynamips and found the same issues with using
distance. My alternative solution was to create a default route from R2 in
OSPF. Then, on R5 I distributed out the specific routes from R2 (except the
new default). R5 then used the routes from R1 as they were more specific. IF
the link to R1 failed the alternative default from R2 is used.
I hope this wasn't too confusing...
cheers
Dinesh
On Sat, Mar 8, 2008 at 2:28 PM, Carlos Alberto Trujillo Jimenez <
carlos.trujillo.jimenez@gmail.com> wrote:
> Hi Group.
>
> I solved task 3.7, but a different way from the Solution Guide that seems
> to
> be incorrect the answer in the solution guide.
>
>
> First, let remember what the task is asking:
>
> - Configure the OSPF domain in such a way that R5 uses R1 to get to VLAN
> 2,6,7,11 AN 367
> - In the case the frame relay circuit between R1 and R5 is down, this
> traffic should be rerouted to R2.
> - Don not use the ip ospf cost, bandwidth, virtual-link, stub, or nssa
> commands to accomplish this.
>
>
> My solution:
>
> In R2 I modified the cost of the area 0 networks that R2 is advertising to
> the area 1 (router 5 is memeber of area 1). As the restriction states to
> not
> use the command "IP OSPF COST", I modifyed the cost, but NOT USING THE
> COMMMAND "IP OSPF COST", so for me it seems my answer is ok, Im not
> violating any restriction.
>
> Router 2:
>
> router ospf 1
> area 1 range 139.1.2.0 255.255.255.0 cost 10000
> area 1 range 139.1.11.0 255.255.255.0 cost 10000
> area 1 range 139.1.0.0 255.255.255.0 cost 10000
> area 1 range 139.1.6.0 255.255.255.0 cost 10000
>
>
> As a result I cheekd R5 routing table and it has entries to vlans 2,6,7,11
> and 367 pointing to its prefered next hop R1 (router 1 is advertising the
> same networks as router 2, but with a better cost).
> I tested shutting down R1 link to the frame-relay network, and the routes
> are reachable now by its next hop R2.
>
>
>
> 2008/3/8, Herbert Maosa <asawilunda@googlemail.com>:
> >
> > Hi Guys,
> >
> > I have tried to lab this again and again and my result seem to disagree
> > with
> > the solution to task 3.7 of IEWB lab 13. So either I may be missing
> > something very fundamental as the output from the solutions guide shows
> > that
> > it should work. So hopefully one of you can shed more light on my gaps
> > here.
> >
> > R1,R2,R6,SW1 ,R3a re originating VLANS 11, 2,6,7 and 367 respectively
> into
> > OSPF . R5 has adjacencies with R1 and R2 and recieving these prefixes.
> The
> > question is configure R5 such that it prefers the path towards R1 and
> only
> > use R2 as a backup.
> >
> > The solution is to lower the OSPF distance for these routes when they
> are
> > learned from R2.
> >
> > *distance 109 150.1.1.1 0.0.0.0 VIA_R1
> >
> > *VIA_R1 is a standard access-list that matches the desired routes.
> > 150.1.1.1is the ospf router-id of R1. Now, when I configure this way,
> > only VLAN 11 (
> > 139.1.0.0/24) has the distance lowered to 109 and R5 prefers this path
> > when
> > R1 is available. This is what I expect to happen and it is what I am
> > seeing
> > in the lab, as my understanding is that in the distance command above ,
> > 150.1.1.1 has to be the advertising router-id, and not the next hop from
> > which you learnt the LSA. So because R1 is only originating VLAN 11, it
> > seems to work that way, but the other routes are not affected even
> though
> > they are learnt from R1 because they are originated form somewhere else.
> >
> > Now, the show command output from the solutions guide seems to show all
> > these prefixes with their distance changed to 109, which is suggesting
> > that
> > the 150.1.1.1 in the distance command would be the router-id of the
> > next-hop
> > router that you learnt the prefixes from, and not necessarily the
> > advertising router.
> >
> > Can someone open my eyes here ? I have tried to find my own asnwer by
> > labbing this over and over again and I can not reproduce the solution
> > provided, even if I copy and paste the config from the solutions guide
> > as-is.
> >
> > Herbert.
> >
> > _______________________________________________________________________
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>
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