Re: OSPF default route multiple processes

Can I ask a question.
What was the design reason for using multiple instances of the OSPF process?

Chris

On 27/07/2013, at 5:26 AM, Marc La Porte <marc.a.laporte_at_gmail.com> wrote:

> Thanks, Jose...
>
> On Fri, Jul 26, 2013 at 9:10 PM, Jose Zamora <joszompr_at_gmail.com> wrote:
>
>> In this case both OSPF process are treated as different routing protocol
>> instances so the router is going to compare de AD of both to select the
>> best route, in case of a tie like in this escenario its going to select the
>> one learned first.
>>
>> Because of this it could work like you expect for a while but a
>> convergence on the network could change the behavior.
>>
>> You could change the AD of one of the process to force it to use the
>> default you want
>>
>> Regards
>>
>> Jose
>>
>>
>> On Fri, Jul 26, 2013 at 11:24 AM, Kristian Francisco <
>> kristian.j.f_at_gmail.com> wrote:
>>
>>> Hey Marc, I would like to take a stab at your questions, but will let some
>>> of the CCIEs with more experience confirm. I would expect the following to
>>> take place:
>>>
>>> Although there are two ospf processes running, there's only one routing
>>> table. I would not expect ospf to treat its rules on route selection
>>> differently. (this is an assumption). For true segmentation, consider
>>> vrfs.
>>>
>>> As you mentioned, the type-1 LSA to be preferred over a type-2 LSA. Once
>>> you make the default routes both of the same type, the following selection
>>> criteria will apply:
>>>
>>> - If type-2 metric is the same, prefer route with better internal cost.
>>> - Directly from RFC: In any case, among the remaining routing table
>>>
>>> entries, select the routing table entry with the least cost; when
>>> there are
>>> multiple least cost routing table entries the entry whose associated
>>> area
>>> has the largest OSPF Area ID (when considered as an unsigned 32-bit
>>> integer) is chosen.
>>>
>>> Best Regards,
>>>
>>> Kristian J. Francisco
>>>
>>>
>>> On Fri, Jul 26, 2013 at 10:20 AM, Marc La Porte <marc.a.laporte_at_gmail.com
>>>> wrote:
>>>
>>>> Rati,
>>>>
>>>> How does it choose between the two processes though?
>>>>
>>>> Cheers,
>>>> Marc
>>>>
>>>> On Fri, Jul 26, 2013 at 7:12 PM, Rati Berikaant Jokhadze
>>>> <iinfo83_at_gmail.com>wrote:
>>>>
>>>>>
>>>>> On 07/26/2013 08:50 PM, Marc La Porte wrote:
>>>>>
>>>>>> 1. What is the order of operation within OSPF to select default
>>> routes
>>>>>> from
>>>>>> different processes?
>>>>>>
>>>>>> 2. How do I ensure the border router ALWAYS takes the default route
>>> from
>>>>>> Area 51 (although it has multiple default routes from Area 0 in it's
>>>>>> database)? Since OSPF metric-type 1 has preference over metric-type
>>> 2,
>>>> do
>>>>>> I
>>>>>> change the metric-type in Area 51 to type 2 and ensure it's always
>>> lower
>>>>>> than from Area 0?
>>>>> 1. First recieved route within process
>>>>>
>>>>> 2. I dont think so , that you can do this , someone will answer
>>>> exactly...
>>>>
>>>>
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>>
>>
>> --
>> Atentamente Jose Zamora Prado
>> Telefono 8252885
>
>
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Received on Sat Jul 27 2013 - 20:51:21 ART