Re: OSPF external type-2 route load balance

From: Scott Smith (hioctane@gmail.com)
Date: Fri Aug 31 2007 - 15:59:08 ART

I neglected to include the border router info

Before (BW equal)

A1(config-subif)#do sh ip ospf border-routers
OSPF Process 1 internal Routing Table
Codes: i - Intra-area route, I - Inter-area route

i 10.1.0.7 [65] via 10.43.1.73, Serial1/0.2, ABR/ASBR, Area 11, SPF 66
i 10.1.0.8 [65] via 10.43.1.61, Serial1/0.1, ABR/ASBR, Area 11, SPF 66

*******************************

After (s1/0.1 BW set to 512)

A1(config-subif)#do sh ip ospf border-routers
OSPF Process 1 internal Routing Table
Codes: i - Intra-area route, I - Inter-area route

i 10.1.0.7 [65] via 10.43.1.73, Serial1/0.2, ABR/ASBR, Area 11, SPF 67
i 10.1.0.8 [195] via 10.43.1.61, Serial1/0.1, ABR/ASBR, Area 11, SPF 67 

-- 
Scott
CCIE #17040 (R&S)

On 8/31/07, Scott Smith <hioctane@gmail.com> wrote:
> 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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> >
>

-- 
Scott
CCIE #17040 (R&S)

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