Subject: Highest IP Address

From: Bhartendu M <[email-masked]>
Date: Wed, 8 Feb 2006 12:27:23 +0530

Hi All,

I am curious to know the logic behind -

Why always HIGHEST IP Address is selected for a tie break like in
1. DR election process in OSPF
2. Default router-id in OSPF 

Is there any advantage using highest IP address over lowest IP address?
Is this a covention or any logic behind this?

Thanks & Regards
Bhartendu M.

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From: Paul Wells <[email-masked]>
Date: Wed, 8 Feb 2006 08:02:35 -0600

Hi Bhartendu,

For DR election I believe the choice was arbitrary.  There just had to 
be a rule that all implementations would apply consistently.  The same 
logic applies to other cases like choosing the highest router ID as the 
NSSA translator.

Choosing a default value for the router ID (or not) is an implementation 
issue, not part of the protocol.  Different vendors are free to use 
other methods.  The important thing is that the router IDs are unique.

Regards,
Paul

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From: Zengjie Kou <[email-masked]>
Date: Thu, 9 Feb 2006 12:13:40 +0800

Hi, Bhartendu,
     I agree your opinion.
     DR election requires a role for a tie break. OSPF adopts the "highest" IP address. The mechanism is similar to other protocols(i.e. IEEE-STP).     
     For "router ID" is special qualification exception unique. if you have good ideas about the router ID, you will solve Aniket's question about "Selection of router id. And behaviour with IPv4 address removal".

Thanks
Kou.