From: Michael Zuo (mzuo@ixiacom.com)
Date: Tue Oct 10 2006 - 19:34:27 ART
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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