From: Michael Zuo (mzuo@ixiacom.com)
Date: Mon Oct 16 2006 - 13:53:16 ART
Just curious, what is the difference between the "ip ospf priority"
under interface and "neighbor priority" under router ospf?
thanks
________________________________
From: david robin [mailto:robindavi@gmail.com]
Sent: Thursday, October 12, 2006 1:57 AM
To: alexeim@orcsoftware.com
Cc: Michael Zuo; Noble, TN; Cisco certification
Subject: Re: neighbor priority commands
Dear All,
yep I mean neighbor proiority without puting any interface ospf priority
commands.
the question was can we achieve the same result without puting ip ospf
priority 0 in spokes interfaces.
I try to do it but I fail every time a DR/BDR connection is established
not /Drother ( I m on the hub router)
I
On 10/11/06, Alexei Monastyrnyi <alexeim@orcsoftware.com> wrote:
Your understanding is quite similar to mine :-)
The question, however, was regarding "neighbor X priority Y" under OSPF
process configuration...
A.
Michael Zuo wrote:
> Here is my understanding (Correct me if I am wrong):
>
> This command influences which router will become DR and is especially
> important in the "non-broadcast" hub and spoke setup. "ip priority 0"
> takes that router out of the DR selection completely. This is the
only
> safe way to go since "ip priority X" command is not pre-emptive and
any
> other value than 0 will produce unpredictable results from DR
selection
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Alexei Monastyrnyi
> Sent: Sunday, October 08, 2006 7:27 AM
> To: david robin
> Cc: Noble, TN; Cisco certification
> Subject: Re: neighbor priority commands
>
> Hi.
>
> Usual way is to set "ip ospf priority 0" on spokes' interfaces towards
> hub router and "neighbor _spoke_IP_ " under ospf process of hub router
> for each spoke. _spoke_IP_ is an IP address of spoke connected NBMA
> interface, not an OSPF router ID of the neighbor. OSPF network type
for
> interfaces should be non-broadcast, if we mean to elect DR.
>
> With this you don't have to use "priority keyword for neighbor
> statement.
>
> Because of limited experience I can not provide an example where such
a
> keyword would be useful. Though it would be interesting to know... :-)
>
>
> HTH
> A.
>
> david robin wrote:
>
>> But the problem is that I try to make the hub router as DR and the
>>
> other
>
>> routers as Drother, but it can't be accomplished, could you tell me
>>
> how can
>
>> we accomplish this, also the documentation CD say the default
priority
>>
> is 0
>
>> not 1 which makes me confused more.
>>
>>
>>
>>
>> On 10/7/06, Alexei Monastyrnyi <alexeim@orcsoftware.com > wrote:
>>
>>
>>> Seems like it is a whole lot of confusion here.. even in CiscoPress
>>>
> :-)
>
>>> From Cisco(r) OSPF Command and Configuration Handbook (CCIE
>>>
> Professional
>
>>> Development)
>>>
>>>
>>> 11-5. neighbor ip-address priority priority
>>>
>>> Syntax Description:
>>>
>>> *
>>>
>>> ip-address IP address of the OSPF neighbor. If a secondary
>>> address is used on the interface, then the primary address must
>>>
> be
>
>>> used with this command because OSPF will only form an adjacency
>>> using the primary address.
>>>
>>> *
>>>
>>> priority The OSPF priority of the neighbor with the given IP
>>> address. The range of values is 0 to 255. _The router with the
>>> lowest OSPF priority on a network will be elected the DR for
the
>>> network._ A priority of zero means that the router is not
>>>
> eligible
>
>>> to be elected the DR or Backup Designated Router (BDR). _The
>>> default priority is 1_.
>>>
>>> Pay attention to _ ... _ statements :-) They seemingly messed up
>>> priority in general and priority defaults for the particular
command.
>>>
>>> From 12.3 DocCD
>>>
>>>
>>>
>>>
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/
> iprrp
>
>> _r/ip2_n1g.htm#wp1036543
>>
>>
>>> *priority*/ number/
>>>
>>>
>>>
>>> (Optional) A number that indicates the router priority value of the
>>> nonbroadcast neighbor associated with the IP address specified.*
*The
>>> default is 0. This keyword does not apply to point-to-multipoint
>>> interfaces.
>>>
>>>
>>> From what I can see on routers (IOS 12.3), for NBMA hub router with
>>> this command applied towards spokes and spokes with default priority
>>>
> 1,
>
>>> you accomplish nothing.
>>>
>>> Just a quick example. For hub router with lo0 9.9.4.4/32 and "ip
ospf
>>> priority 3" on NNBMA interface, after "clear ip ospf proc" on all
>>>
> three
>
>>> boxes, I have, as expected.
>>>
>>> BB4#sh ip ospf nei
>>>
>>> Neighbor ID Pri State Dead Time Address Interface
>>> 9.9.2.2 1 FULL/BDR 00:01:54 9.9.123.2 Serial0
>>> 9.9.1.1 1 FULL/DROTHER 00:01:35 9.9.123.1 Serial0
>>> BB4#sh run | beg router
>>> router ospf 100
>>> log-adjacency-changes
>>> network 9.9.123.0 0.0.0.255 area 0
>>> neighbor 9.9.123.2 priority 1
>>> neighbor 9.9.123.1 priority 2
>>>
>>> After "clear ip ospf proc" on the hub router we have.
>>> BB4#sh ip ospf nei
>>>
>>> Neighbor ID Pri State Dead Time Address Interface
>>> 9.9.2.2 1 FULL/DR 00:01:53 9.9.123.2 Serial0
>>> 9.9.1.1 1 FULL/BDR 00:01:59 9.9.123.1 Serial0
>>>
>>> Which is also expected. But I don't see any place where " neighbor
>>>
> ...
>
>>> priority.. " comes into play.
>>>
>>> It is probably useful for more complex mesh than hub and spoke.
>>>
>>> A.
>>>
>>>
>>> Noble, TN wrote:
>>>
>>>
>>>> The priority command does the same thing irrespective of the place
>>>>
> it is
>
>>>> applied. I mean, ip ospf priority 0 and neighbour 1.2.3.4 priority
0
>>>> (optional and 0 is defaul) should do the same for us.
>>>>
>>>> Thank you,
>>>>
>>>> -Noble
>>>>
>>>>
>>>> On 10/6/06, david robin <robindavi@gmail.com> wrote:
>>>>
>>>>
>>>>
>>>>> Dear all,
>>>>> I m confused with neighbor priority command, I configured R1 as
>>>>> frame-relay
>>>>> hub, R2 and R5 as spokes. interfaces are non-broadcast so you must
>>>>>
> use
>
>>>>> neighbor command.
>>>>>
>>>>> because R1 is the hub so prioriies of the two other routers must
be
>>>>>
> set
>
>>>>>
>>>>>
>>> to
>>>
>>>
>>>>> 0
>>>>> in order to make R1 as the DR, I know we can accomplish this by
>>>>>
> using
>
>>>>>
>>>>>
>>> ip
>>>
>>>
>>>>> ospf priority 0 under R2 and R5 serial interfaces.
>>>>>
>>>>> the question is does the neighbor priority command has any
relation
>>>>>
> to
>
>>>>> DR/BDR election, and if so what is the relation between it and ip
>>>>>
> ospf
>
>>>>> priority 0, does ospf priority 0 override it or what ?
>>>>>
>>>>> and what is the use on neighbor priority command if is has no
>>>>>
> relation
>
>>>>>
>>>>>
>>> to
>>>
>>>
>>>>> DR/BDR election
>>>>>
>>>>> many thanks
>>>>>
>>>>>
>>>>>
>
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