From: Annu (annu_roopa@xxxxxxxxx)
Date: Fri Dec 28 2001 - 02:57:27 GMT-3
Yves,
Looks like the reason u mentioned is the correct one.i
tried recreating the case with the serial1 thru area 0
and it works fine.
Also i think u might not have been able to reconstuct
the lab as there would have been loops and Convergence
on a path was not predictable (in fact today when i
rebooted the routers they were selecting diffrent path
than yday and it took me long time to figure out the
loops and fix it.Same as Doyle's case on Page 787 for
loops.
Now it works as expected by selecting the lower cost
E1 path.Thanks for ur replies and time.
Annu
--- Yves@Fauser.de wrote:
> Annu,
>
> I'm not able to reconstruct your problem in a Lab,
> but the reason should
> be that OSPF prefers and Intra-Area path more than
> an Inter-Area path.
> On R5 your path through R4 is a Intra-Area path,
> your path through R9 is
> an Inter-Area path. I think thats why the higher
> metric path is choosen.
> Try putting the Ser1's of R5 and R9 from Area 1 to
> Area 0, and look if the
> path trough R4 is choosen then.
>
> Reference : Jeff Doyle, Routing TCP/IP Vol.1, Page
> 490
>
> Good luck,
> Yves
>
>
>
>
>
> Annu <annu_roopa@yahoo.com>
> Sent by: nobody@groupstudy.com
> 27.12.2001 02:46
> Please respond to Annu
>
>
> To:
> cc: annu_roopa@yahoo.com
> Subject: OSPF route Selection ?
>
>
> Group,
>
> This is something i am unable to interpret.IF
> someone
> can tell me why this is happening ? Here goes the
> scenario.
>
> e0 e0 s0
>
> R9------------------R11------R10--20.1.1.1
> | <-area 0 ---------> |s1
> s1 | |
> R5------------------R4-------|
> e0 e0 s1
>
>
> R9/R5 are ABR's and connected to R11/R4( both
> ASBR's)
> E0 of both in area 0; Ser1 of ABR's in area 1.
> R10 is connected to loopback 20.1.1.1.
> R4 introduces type E1 route into R5.
> R11 introduces type E1 route into R9.
>
> Cost of E0 on R5=200;all other interfaces have
> default
> cost.
>
> Now R5 gets two E1 routes,one with cost 220(200+20)
> from R4 and other with cost 94(64+10+20)from R9.
>
> I thought the E1 route thru R9 and R11 will be the
> preferred path as its same type and lower metric but
> R5 seems to go thru R4.
>
> Am i wrong in understanding ? or what is missing ?
>
> Here are the route tables:
> r5#show ip route
> 55.0.0.0/16 is subnetted, 1 subnets
> C 55.1.0.0 is directly connected, Serial1
> O E1 20.0.0.0/8 [110/220] via 172.16.1.18, 00:03:11,
> Ethernet0
> 172.16.0.0/28 is subnetted, 1 subnets
> C 172.16.1.16 is directly connected, Ethernet0
> 192.168.1.0/28 is subnetted, 2 subnets
> O E1 192.168.1.0 [110/220] via 172.16.1.18,
> 00:03:11, Ethernet0
> O E1 192.168.1.16 [110/220] via 172.16.1.18,
> 00:03:11, Ethernet0
>
> When Ethernet fails ?
>
> r5#show ip route
> Gateway of last resort is not set
>
> 55.0.0.0/16 is subnetted, 1 subnets
> C 55.1.0.0 is directly connected, Serial1
> O E1 20.0.0.0/8 [110/94] via 55.1.1.2, 00:00:23,
> Serial1
> 172.16.0.0/28 is subnetted, 1 subnets
> O IA 172.16.1.0 [110/74] via 55.1.1.2, 00:00:23,
> Serial1
> 192.168.1.0/28 is subnetted, 2 subnets
> O E1 192.168.1.0 [110/94] via 55.1.1.2, 00:00:23,
> Serial1
> O E1 192.168.1.16 [110/94] via 55.1.1.2,
> 00:00:23,
> Serial1
>
>
>
>
> =====
> Thanks in advance for ur time and replies.
> Annu.
>
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:32:48 GMT-3