From: Leo Leung (leo0430453@gmail.com)
Date: Mon Oct 13 2008 - 18:15:11 ART
Reza,
OSPF cost and metric are not exactly the same. As far as the value
goes, cost can go as high as 2**16=65535, but metric can go as high as
2**24=16777214, based on the path, redistribute metric or
default-metric being used, remote end sees a metric multiply factor of
cost.
Just my 2 cents
leo
#22227
On Mon, Oct 13, 2008 at 9:13 AM, Reza Toghraee <reza@toghraee.com> wrote:
> Yes I did, and also I saw that if you put "ip ospf cost 65535" on the
> loopback and the transit link, the neighbor router will see the route with
> metric of 131070.
> Also I connected 3 routers together with OSPF, with interfaces having "ip
> ospf cost 65535". In the last router I saw the loopback of 1st router with
> metric of 196605 (3*65535)
>
> Now the question is that the Metric field in LSA packet is 16 bits, how it
> carries more than 16 bit (65535) ?????
>
>
>
>
> -----Original Message-----
> From: Richard L. Pickard [mailto:richardlpickard@hotmail.com]
> Sent: Monday, October 13, 2008 7:54 PM
> To: 'Reza Toghraee'
> Subject: Re: OSPF Question, how to prefer inter area routes, over intra area
>
>
>
> but if there is no other path your data will use that path.
>
> This is why it is good to have real routers - you can mock up stuff like
> this & see how it works.
>
> R
>
> ----- Original Message -----
> From: "Scott Morris" <smorris@internetworkexpert.com>
> To: "'Reza Toghraee'" <reza@toghraee.com>
> Cc: <ccielab@groupstudy.com>
> Sent: Monday, October 13, 2008 9:18 AM
> Subject: RE: OSPF Question, how to prefer inter area routes, over intra area
>
>
>> Correct. You are setting your links cost (thus the router advertisements)
>> to the maximum value which basically says "I'm here, but don't use me!"
>>
>> -----Original Message-----
>> From: Reza Toghraee [mailto:reza@toghraee.com]
>> Sent: Monday, October 13, 2008 8:01 AM
>> To: 'Scott Morris'
>> Cc: ccielab@groupstudy.com
>> Subject: RE: OSPF Question, how to prefer inter area routes, over intra
>> area
>>
>> Yes I manipulated, and changed the cost of other links to a higher value.
>> But I didn't check the "sh ip ospf virt". Now I understand why it doesn't
>> go
>> on virtual link by default. BECAUSE the COST of VIRTUAL-LINKS is
>> significantly higher.
>>
>> 1 more question : What does "ip ospf cost 65535" mean? Does it mean that
>> NO
>> TRAFFIC will pass the link even if this is the only operational link?
>>
>> Regards
>> Reza
>>
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> Scott Morris
>> Sent: Monday, October 13, 2008 3:52 PM
>> To: 'Reza Toghraee'
>> Cc: ccielab@groupstudy.com
>> Subject: RE: OSPF Question, how to prefer inter area routes, over intra
>> area
>>
>> Once you have your virtual link, you'll notice that the cost to the routes
>> is significantly higher though. Have you tried manipulation in this
>> sense?
>> (sh ip ospf virtual-link)
>>
>> -----Original Message-----
>> From: Reza Toghraee [mailto:reza@toghraee.com]
>> Sent: Monday, October 13, 2008 6:40 AM
>> To: smorris@internetworkexpert.com
>> Cc: ccielab@groupstudy.com
>> Subject: RE: OSPF Question, how to prefer inter area routes, over intra
>> area
>>
>> It's a Lab scenario, I crated myself of course its amazing ;)
>>
>> I found this Method, and its working
>>
>> 1) R3 peers with R2 over a virtual link on Area23
>> 2) R1 peers with R3 over a virtual link on Area13
>> 3) R1 puts ospf cost 100 on its 64K link to R2.
>>
>> So R1 receives R2' Loopback interface over its 64K link and also from
>> Virtual link from R3. Both as intra-area.
>> By default it should prefer the virtual link, and if not we can use ip
>> ospf
>> cost to change metrics.
>>
>>
>> -----Original Message-----
>>
>> You'll ALWAYS get intra-area over inter-area. That's the way the spec is
>> written, and it just plain makes sense. :)
>>
>> Was it intentional to make the slowest path the "backbone" of your OSPF
>> network?
>>
>> Scott
>>
>> -----Original Message-----
>> 174.1.13.0/24
>> _____ __________________________ _____
>> | R1| | | | R2|
>> |___|---| A R E A 0 |--------|___|
>> | | This link is a 64K | |
>> | |__________________________| |
>> | ____|______
>> __|__________ | |
>> | | | |
>> | AREA13 | _______| |
>> | | 174.1.31.1 V13 | |
>> | 10Mbps | | |
>> |____________| | A R E A 23 |
>> | | |
>> __|__ |_________________| 10Mbps BW |
>> | R3| | |
>> |___|-------|___________________________________|
>> 174.1.43.4 /24 V 43
>>
>>
>>
>> R2 is advertising it Looback in OSPF AREA 0 ,with network command.
>> R1 will route through the AREA 0, on 64K Link to reach R2' Loopback 0.
>>
>> Question 1 : how to make R1, route through R3 on Area 13, and Area 23 to
>> reach R2' Loopback ?
>>
>> What I tried :
>> 1) I tried to use distance on the routes coming from R2, to change them to
>> 130, but seems the OSPF first chooses the InterArea route over intra area,
>> then applies the distance.
>> 2) I used a distribution-list on R1 to filter the routes coming from R2.
>> Its
>> working but if the Link between R1,R3 is disconnected, then R1 cannot
>> reach
>> R2' Loopback
>>
>>
>> Question 2: R2 Advertises its Loopback with Redistribution as E1.
>>
>> What I tried :
>>
>> 1) I tried to change the costs on 64K Link to very high. But I don't
>> remember it worked or not.
>>
>>
>> Waiting for your solutions.
>> Reza Toghraee
>>
>>
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