Subject: [VRRP] [Fwd: Address Owner Exception]

From: Scott Kimble <[email-masked]>
Date: Mon, 05 Jun 2006 09:12:44 -0700

RESEND

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Subject: Address Owner Exception
From: Scott Kimble <[email-masked]>
To: [email-masked]
Date: Thu, 01 Jun 2006 09:39:57 -0700

In
7.1.  Receiving VRRP Packets

in the misconfiguration check:
MAY verify that "Count IP Addrs" and the list of IP Address matches the 
IP_Addresses configured for the VRID

The following doesn't seem quite right to me.
If the above check fails, the receiver SHOULD log the event and MAY 
indicate via network management that a misconfiguration was detected.  
If the packet was not generated by the address owner (Priority does not 
equal 255 (decimal)), the receiver MUST drop the packet, otherwise 
continue processing.

My interpretation is that the exception for allowing Advertisements from 
the address owner to reach the Protocol State Machine when the Virtual 
Router is misconfigured is that it allows the Virtual Router to elect a 
Master and prevents multiple Masters.

I have two issues with this.  Of course we assume a misconfiguration.
1)  Allowing the Advertisement from the address owner to reach the 
Protocol State Machine would result in the following
1a) On the Master the Advertisement would be dropped.
1b) On the Backup the Advertisement would cause a reset of the 
Master_Down_Timer to Master_Down_Interval.

In both cases we get the desired affect and the value of the exception 
is to drop the packet earlier in processing.  Fair enough, but this 
leads us to my second concern.

2) The above assumes that one of the VRRP Routers is an address owner.  
Suppose the address is Virtual and there is no address owner.  In this 
case, the exception would cause each of the VRRP Routers to drop the 
Advertisement.  Since they transition from Init to Backup by default, 
each would eventually detect a Master failure and send an 
Advertisement.  Each would also drop any Advertisement received, since 
the Advertisement will not have come from an address owner.  In this 
case all VRRP Routers will transition to Master.

This would be avoided if the Advertisements were allowed to reach the 
Protocol State Machine where Master Election rules would apply.

Am I missing something in the utility of the address owner exception?

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