From: Gary Duncanson (gary.duncanson@googlemail.com)
Date: Fri Aug 31 2007 - 16:58:28 ART
Thanks for that Scott.
Looks like this demonstrates this rather well, at least how I read it.
From OSPF Design Guide on CCO.
sic 'External routes fall under two categories, external type 1 and external
type 2. The difference between the two is in the way the cost (metric) of
the route is being calculated. The cost of a type 2 route is always the
external cost, irrespective of the interior cost to reach that route.'
Rgds
Gary
----- Original Message -----
From: "Scott Smith" <hioctane@gmail.com>
To: "Sadiq Yakasai" <sadiqtanko@gmail.com>
Cc: "Joseph Brunner" <joe@affirmedsystems.com>; "Herbert Maosa"
<asawilunda@googlemail.com>; "ISolveSystems" <support@isolvesystems.com>;
"Cisco certification" <ccielab@groupstudy.com>
Sent: Friday, August 31, 2007 7:49 PM
Subject: Re: OSPF external type-2 route load balance
> Bingo!
>
> A1 learns 100.100.100.0 from both 10.43.1.61 & 10.43.1.73.
>
> Before - BW 1536 to both ASBRs
>
> A1(config-router)#do sh ip route ospf
> 100.0.0.0/24 is subnetted, 1 subnets
> O E2 100.100.100.0 [110/20] via 10.43.1.61, 00:00:36, Serial1/0.1
> [110/20] via 10.43.1.73, 00:00:36,
> Serial1/0.2
>
>
> After - Dropped BW to 512 on s1/0.1
>
> A1(config-subif)#do sh ip route ospf
> 100.0.0.0/24 is subnetted, 1 subnets
> O E2 100.100.100.0 [110/20] via 10.43.1.73, 00:00:06, Serial1/0.2
>
>
> Then changed BW back to 1536 on s1/0.1 (now both are equal again)
>
> A1(config-subif)#do sh ip route ospf
> 100.0.0.0/24 is subnetted, 1 subnets
> O E2 100.100.100.0 [110/20] via 10.43.1.73, 00:00:02, Serial1/0.2
> [110/20] via 10.43.1.61, 00:00:02,
> Serial1/0.1
>
> The metric is a constant 20, however, for the externals OSPF also uses
> the cost to the ASBR.
>
> --
> Scott
> CCIE #17040 (R&S)
>
>
> On 8/31/07, Sadiq Yakasai <sadiqtanko@gmail.com> wrote:
>> Can you show the Type 4 LSA database as well?
>>
>> I think the cost to the ASBR has a role to play in selecting 2 Type 5
>> LSA's reporting the same prefix.
>>
>> I am not quite sure about this though.
>>
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