Subject: [VRRP] terminology questions

From: Huafeng Lu <[email-masked]>
Date: Mon, 14 Jul 2008 17:39:04 +0800

Hi, VRRPers,

I have some questions about the terms used in RFC 3768 and draft 02.

1. "IPvX address(es) associated with the virtual router" vs. "the
virtual router's IPvX address(es)".

Do they mean the same thing? I think so, but can anyone confirm this?

2. "Primary IP Address".

It seems this concept applies only for IPv4? In IPv6 there's no such
concept and we just call its counterpart "the link-local address"?

Thanks.
--
Huafeng
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From: "Stephen Nadas" <[email-masked]>
Date: Mon, 14 Jul 2008 06:57:14 -0500

Hi Huafeng, 

> 1. "IPvX address(es) associated with the virtual router" vs. 
> "the virtual router's IPvX address(es)".
> 

I think the term "IPvX address(es) associated with the virtual router"
is consistently used in -02 to mean the addresses that are protected by
VRRP, that is, if the master fails, it is packets addressed to these
addresses that the backup will forward.  

The term "the virtual router's IPvX address(es)" seems to only be used
in section 1.6: 

   IP Address Owner        The VRRP router that has the virtual router's
                           IPvX address(es) as real interface
                           address(es).  This is the router that, when
                           up, will respond to packets addressed to one
                           of these IPvX addresses for ICMP pings, TCP
                           connections, etc.

Where it means the same. 

> 2. "Primary IP Address".
> 
> It seems this concept applies only for IPv4? In IPv6 there's 
> no such concept and we just call its counterpart "the 
> link-local address"?

To my understanding, concept only applies to IPv4.  I'm not sure that I
agree with 'and we just call its counterpart "the link-local address"'
part of this bcos in general the semantics of IPv4 address != semantics
of IPv6 link-local address. 

Regards,
Steve

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From: Huafeng Lu <[email-masked]>
Date: Mon, 14 Jul 2008 21:54:26 +0800

>                            of these IPvX addresses for ICMP pings, TCP

OK, I see.

> of IPv6 link-local address. 

I think the semantics of the "Primary IP address" is to act as the 
source IP address of the VRRP advertisements. The IPv6 link-local 
address also serves for this purpose, right?
Why does the concept only apply for IPv4? I don't see a problem 
extending this concept to ipv6.
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From: "Stephen Nadas" <[email-masked]>
Date: Mon, 14 Jul 2008 10:19:40 -0500

> > To my understanding, concept only applies to IPv4.  I'm not 
> sure that 
> > I agree with 'and we just call its counterpart "the 
> link-local address"'
> > part of this bcos in general the semantics of IPv4 address != 
> > semantics of IPv6 link-local address.
> 
> I think the semantics of the "Primary IP address" is to act 
> as the source IP address of the VRRP advertisements. The IPv6 
> link-local address also serves for this purpose, right?
> Why does the concept only apply for IPv4? I don't see a 
> problem extending this concept to ipv6.
> 

Huafeng, 

Okay, I think see that what your are saying is in the context of VRRP,
and in that sense I can agree.  But "primary IP address" is (imho, far)
more widely used and I was thinking about those semantics, so I prefer
not to try to extend this concept as I think the confusion would
outweigh the benefit.  

Opinion from others on the list? 

Thanks,
Steve