From: Alexei Monastyrnyi (alexeim@orcsoftware.com)
Date: Sat Oct 07 2006 - 09:43:46 ART
Seems like it is a whole lot of confusion here.. even in CiscoPress :-)
From CiscoB. OSPF Command and Configuration Handbook (CCIE Professional
Development)
11-5. neighbor ip-address priority priority
Syntax Description:
*
ip-addressb 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.
*
priorityb 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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>
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