Subject: [VRRP] Multiple Virtual Address Question

From: "Nigg, Gary" <[email-masked]>
Date: Thu, 15 Feb 2007 17:29:53 -0500

VRRP Mailing List,
 
I have come across a VRRP configuration and am curious how the VRRP
protocol (RFC 3768) should handle the following situation.  Within a
single Virtual Router, there is a single VRRP advertisement that is
transmitted by the VRRP Master.  This advertisement contains only one
priority field for the multiple Virtual Addresses that may be present in
the packet.   How should the protocol function if the set of Virtual
Addresses contains IP addresses that are both "owned" and "not-owned" by
the local VRRP Router?  Does the protocol strictly prohibit this
scenario and require that 2 VRIDs be defined on the common LAN? Section
3 (VRRP Overview) paragraph 2 seems to hint at this.  Or is this an
allowable configuration?  And if so, what should the VRRP Priority value
be in the corresponding VRRP Advertisement (255 or 1-254)?  I have seen
3 different implementations by various vendors:
 
1) Reject this configuration
2) If any one of the virtual addresses within the set is locally owned,
set the Priority = 255
3) If any one of the virtual addresses within the set is NOT locally
owned, set the Priority to the configured value (1-254; default = 100) 
 
If #2 or #3 are implemented, it further adds to the confusion as what to
do in this situation based on Section 7.1 (Receiving VRRP Packets):
MUST verify that the VRID is configured on the receiving interface and
the local router is not the IP Address owner (Priority equals 255
(decimal)).
 
In other words, is a non-local virtual-address in #2 now considered an
IP owner because the Priority is 255?  I understand that this can create
multiple VRRP Masters for a single Virtual Router but would like some
feedback.  It seems the only logical choice is to require #1.  FYI...The
configuration that brought this question up had a VRID using 2 routers
with physical interface IP addresses A & B while the virtual addresses
were A & C.
 
Thanks in advance for your help.
 
Sincerely,
Gary Nigg
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From: "Don Provan" <[email-masked]>
Date: Thu, 15 Feb 2007 15:31:46 -0800

>How should the protocol function if the set of Virtual Addresses
>contains IP addresses that are both "owned" and "not-owned" by
>the local VRRP Router?

The set of IP addresses in any given Virtual Router are all owned
by the same node. What you are describing is a configuration with
multiple Virtual Routers, each requiring its own VR ID.

-don provan

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From: Muneer <[email-masked]>
Date: Thu, 22 Feb 2007 21:39:45 +0530

> multiple Virtual Routers, each requiring its own VR ID.

Can you help me to find out the priority in router A in the following scenario?

Router1 has IP address A, router2 has IP address B. Now, I create a
virtual router with associated IP as A and C.

Thanks in advance.

-Muneer
-- 
Imagination is more important than knowledge...

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From: Muneer <[email-masked]>
Date: Fri, 23 Feb 2007 08:17:14 +0530

On 2/23/07, Don Provan <[email-masked]> wrote:
> I'm not sure what you're asking.

My intention is to achieve a secondary IP address using VRRP, without
having a support for it in actual IP.without assigning A&C(as in the
previous mail) to the actual interface, i would like to achieve it in
the following way.
Assign address A to router 1. Assign vrrp associate IP's A&C to VR1 in
routerA. I will ensure that C will not be assigned to any router. This
configuration ensures that all the ARP requests to A&C will be replied
with virtual MAC. Hence I have a secondary IP address in router 1
(only) for forwarding the packet. Is this extension is a violation to
standards? Or do I really need to use another VRID for C? The problem
in using a different VRID is that it will not ensure both the
instanses are masters in a single router which is my requirement for
secondary IP.

Thanks in advance
Muneer

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From: "Arnab Bakshi" <[email-masked]>
Date: Fri, 23 Feb 2007 09:48:25 +0530

> virtual router with associated IP as A and C.

+++arnab:
 What my understanding is that if you make IP Address A as primary
address of Virtual Router then priority should be 255, for IP Address
C the priority will be 100(default).

Thanks
Arnab

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From: "Don Provan" <[email-masked]>
Date: Fri, 23 Feb 2007 10:25:50 -0800

> routerA. I will ensure that C will not be assigned to any router.

I guess I wasn't clear enough. Priority is assigned to a router, not to
an address. So a router must own all addresses in a VR or none of them.
If you want it to own one but not another, you use two VRs.

> Hence I have a secondary IP address in router 1
> standards?

I suppose you could call it a violation of the standard, but the
important point is that there's no way to express it: the protocol
has a priority that expresses the router's relation to the VR: there
simply is no concept of (and no field to express) a router's
"priority" for a particular address.

> Or do I really need to use another VRID for C? The problem

Then Router1 should own C. Is there some problem with that?

Didn't I take this conversation off line? Why do you think
the whole group needs to discuss it?

-don provan