From: Pierre-Alex (paguanel@hotmail.com)
Date: Fri Jun 16 2006 - 15:37:02 ART
For info in case my diagram arrives messed up, R3 and R4 are both in Area
34.
Pierre-Alex
----- Original Message -----
From: "Pierre-Alex" <paguanel@hotmail.com>
To: "Petr Lapukhov" <petr@internetworkexpert.com>; <vdadlaney@gmail.com>
Cc: <ccielab@groupstudy.com>
Sent: Friday, June 16, 2006 8:27 PM
Subject: Re: type 3 LSA from Area 0 vs. type 3 LSA from non Area 0
> Yes, agree Petr, but your topology is different than mine and is not
> testing
> the same thing. :)
>
> I am evaluating inter-area routes, Type IA via an Area 0 versus
> inter-area
> routes, Type IA via a non-Area 0 (virtual-link)
>
>
> I have re-written the case study for clarity:
>
>
> Area 12 (network 10.1.2.0)
> |
> R2---virtual-link area 23---------R3
> | |
> | |Area34
> ----Area 0----------------------------R4
>
>
> The purpose is to evaluate the path to network 10.1.2.0 from R4
>
> R4 receives information from network 10.1.2.0 from R2 and R3
>
> I have set a really high cost on R4 interface in area 0 towards R2.
>
> The route chosen is yet via R2. See info below
>
> For me:
>
> Pierre-Alex
>
>
> r4#sh ip route 10.1.2.0
> Routing entry for 10.1.2.0/24
> Known via "ospf 100", distance 110, metric 65001, type inter area ---->
> LOOK
> AT THE COST
> Last update from 10.2.4.2 on Serial0/0.402, 00:22:18 ago
> Routing Descriptor Blocks:
> * 10.2.4.2, from 150.1.2.2, 00:22:18 ago, via Serial0/0.402
> Route metric is 65001, traffic share count is 1
>
>
>
> Summary Net Link States (Area 0)
>
> Routing Bit Set on this LSA ----> LSA CHOSEN - WILL BE USED FOR ROUTING
> TABLE
> LS age: 858
> Options: (No TOS-capability, DC, Upward)
> LS Type: Summary Links(Network)
> Link State ID: 10.1.2.0 (summary Network Number)
> Advertising Router: 150.1.2.2
> LS Seq Number: 8000000C
> Checksum: 0x6B1D
> Length: 28
> Network Mask: /24
> TOS: 0 Metric: 1
>
>
>
> Summary Net Link States (Area 34)
>
> LS age: 1533
> Options: (No TOS-capability, DC, Upward)
> LS Type: Summary Links(Network) ---------------> THIS IS FROM R3, THE ABR
> Link State ID: 10.1.2.0 (summary Network Number)
> Advertising Router: 150.1.3.3
> LS Seq Number: 80000001
> Checksum: 0x126F
> Length: 28
> Network Mask: /24
> TOS: 0 Metric: 782
>
>
>
>
>
>
> ----- Original Message -----
> From: Petr Lapukhov
> To: Pierre-Alex
> Cc: ccielab@groupstudy.com
> Sent: Friday, June 16, 2006 8:09 PM
> Subject: Re: type 3 LSA from Area 0 vs. type 3 LSA from non Area 0
>
>
> Pierre,
>
> Here is a simple scenario to demostrate the idea:
>
> Diagram
> ---
>
> Lo5
> |
> R5
> | \___R3
> | /
> R4
>
> Configuration:
>
> 1) R4 and R5 are connected via link in Area 1 (with Serial 0/1
> interfaces)
> This path has Cost = 1.
>
> 2) R3, R4 and R5 form Area 0 (with Serial 0/0 interfaces at R4, R5).
> Cost has default value.
>
> 3) R5 has Loopback5 (164.1.155.5/32) in Area 5.
>
> The task is to evaluate how R4 routes to Lo5, with and w/o virtual-link
> between R4 and R5. I want put more output, since it's easy to
> simulate both cases.
>
> --
>
> First case: NO virtual link over Area 1.
>
> Rack1R4#show ip route 164.1.155.5
> Routing entry for 164.1.155.5/32
> Known via "ospf 1", distance 110, metric 846, type inter area
> Last update from 164.1.34.3 on Serial0/0, 00:07:24 ago
> Routing Descriptor Blocks:
> * 164.1.34.3, from 150.1.5.5, 00:07:24 ago, via Serial0/0
> Route metric is 846, traffic share count is 1
>
> Path via Area 0 is preferred regardless or cost.
>
> ---
>
> Put a virtual link from R4 to R5 via Area 1 and check routes
> again:
>
> Rack1R4#show ip ospf virtual-links
> Virtual Link OSPF_VL2 to router 150.1.5.5 is up
> Run as demand circuit
> DoNotAge LSA allowed.
> Transit area 1, via interface Serial0/1, Cost of using 1
> Transmit Delay is 1 sec, State POINT_TO_POINT,
> .....
>
> Rack1R4#show ip route 164.1.155.5
> Routing entry for 164.1.155.5/32
> Known via "ospf 1", distance 110, metric 2, type inter area
> Last update from 164.1.45.5 on Serial0/1, 00:00:29 ago
> Routing Descriptor Blocks:
> * 164.1.45.5, from 150.1.5.5, 00:00:29 ago, via Serial0/1
> Route metric is 2, traffic share count is 1
>
> The "best" path is now chosen, because LSAs flow through "Area 0 put
> over Area 1".
>
> --
> Petr Lapukhov, CCIE #16379
> petr@internetworkexpert.com
>
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