Re: VRRP - Multiple Masters Question

I agree with you that protocols should be resilient to configuration 
differences between nodes,
and I think the ideal solution is what you suggested (use the timer as 
advertised by the master)
rather than what's in the spec (discard messages that disagree with your 
setting, so that
multiple masters will be elected, ignoring each others' messages). 
Especially in conjunction with
bridges, multiple masters are dangerous.

This was brought up on the mailing list before I was watching this 
group, and somehow
the discussion fizzled out. I think the subsecond timer draft is a good 
excuse to revisit this,
and make sure, if the WG really wants to keep the behavior as it is, 
that it is doing it
consciously.

So please, people, speak up about which behavior you prefer:

a) discard (and log an error) if the value advertised in the VRRP 
message disagrees with your
configured value for hello timer....this is what is currently specified
b) use the interval advertised by the master, for as long as it is master

If we switch to b), then another decision is whether that is configured 
misconfiguration or not,
i.e., if an error should be logged.

Radia





Hott, Robert W CIV B35-Branch wrote:

> I am in the process of updating a draft for sub-second timers for VRRP 
> for IPv4. An area that I have struggled with has been how to deal with 
> legacy devices that might be on a network with devices that use 
> sub-second timers. In thinking out this issue for this new draft, I 
> noticed something that seems to a problem with the current RFC. The 
> interesting area in RFC 3768 is section 7.1 on receiving VRRP packets.
>
> The issue is this. Suppose that I have a master router configured with 
> an advertisement interval of 1 second. I have two more routers 
> configured as backups. One is configured with an advertisement 
> interval of 2 seconds and another is configured with an advertisement 
> interval of 3 seconds.
>
> I know that this is problematic but it could happen. Anyway, the 
> master would send an advertisement. Based upon section 7.1, both of 
> the backups would discard this advertisement and would report the 
> misconfiguration. Since the advertisement would be discarded, both 
> would eventually transition to masters. The end result would be three 
> masters, since the state machine would not act on the advertisement.
>
> Did I interpret this correctly? I would think that you would not want 
> to discard the advertisement because of the wrong setting. I would 
> think you would want to use the interval of the master, at least until 
> you assume the role of the master.
>
> Bob Hott
>
> *Robert (Bob) W. Hott*
> *NSWC-DD*
> *Code B35, Bldg. 1500A/122A*
> *17320 Dahlgren Road*
> *Dahlgren, VA 22448-5100*
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> *540-653-8673 (FAX)*
> *[email protected] (E-mail)*
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