Subject: [VRRP] Backup->Master transition and ARP reply question

From: Evan Gilman <[email-masked]>
Date: Mon, 20 Feb 2012 15:21:50 -0500

Hello all. I have a couple quick questions for you, hopefully there are 
still people subscribed to this list that know the answers.

1. Section 8.1.2 (Host ARP Requests) of RFC 5798 states that "...the 
source address of the Ethernet frame of this ARP response is the 
physical MAC address of the physical router", however I've observed ARP 
responses with an Ethernet source of the Virtual MAC in products 
claiming 5798 compliance - is this required for compliance?

2. Section 6.4.2 (Backup) of RFC 5798 has three or four actions to take 
on the 'If Master_Down_Timer fires' condition, the last of which is 
'Transition to the Master state', and the first of which is 'Send an 
advertisement'. Are these actions written in strict order? In other 
words, must the actions be executed sequentially in order to be 
determined 5798 Compliant? Seems to me that they would. It also seems to 
me that this question should be answered by some sort of RFC guideline, 
however I've yet to find one.

Thanks in advance for your time, it's very much appreciated.

--
evan

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From: Stephen Nadas <[email-masked]>
Date: Wed, 22 Feb 2012 09:14:55 -0500

Hi Evan,

This list is quiet but still the right place for this question. 

IMO the answer to the 1st questions is yes. 

For the 2nd question I guess (in v4 case) you are seeing grat arps before the advertisement from the router assuming vrrp mastership.  My guess would be that the original intent was that the steps were intended to be followed in order but I do not know this for sure.  Remember that 5798 was edited into 1 doc from the v4 rfc and the v6 draft; if there had been a statement in one or the other of the src docs wrt your question I think it would have made it into 5798.  
    
Thanks,
Steve 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Evan Gilman
Sent: Monday, February 20, 2012 3:22 PM
To: [email-masked]
Subject: [VRRP] Backup->Master transition and ARP reply question

Hello all. I have a couple quick questions for you, hopefully there are still people subscribed to this list that know the answers.

1. Section 8.1.2 (Host ARP Requests) of RFC 5798 states that "...the source address of the Ethernet frame of this ARP response is the physical MAC address of the physical router", however I've observed ARP responses with an Ethernet source of the Virtual MAC in products claiming 5798 compliance - is this required for compliance?

2. Section 6.4.2 (Backup) of RFC 5798 has three or four actions to take on the 'If Master_Down_Timer fires' condition, the last of which is 'Transition to the Master state', and the first of which is 'Send an advertisement'. Are these actions written in strict order? In other words, must the actions be executed sequentially in order to be determined 5798 Compliant? Seems to me that they would. It also seems to me that this question should be answered by some sort of RFC guideline, however I've yet to find one.

--
evan

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From: Evan Gilman <[email-masked]>
Date: Wed, 22 Feb 2012 12:32:56 -0500

Stephen -

Great, thanks for the information. One more question. If ARP Responses 
should be sent with an Ethernet source MAC of the physical router, does 
that also apply for the Gratuitous ARPs sent before transition to 
Master? The document is not very clear on that point, especially in that 
section 8.1.2 mandates an Ethernet SA of the physical MAC for ARP 
Response, but does not mention ARP Request (Gratuitous or not). 
Hopefully this one is a little easier... thanks again for your input.

--
evan