Subject: primary key for virtual router

From: Vivek Menezes <[email-masked]>
Date: Tue, 28 Jul 1998 19:05:41 -0700 (PDT)

Hi,
	In the draft for RFC 2338 a virtual router is described as "An
abstract object that consists of a virtual router identifier and
a set of ip addresses across a common lan"
	Question is, is the "vrid" the primary key to access this object.
Should vrrp be implemented such that the router can setup virtual routers
on different interfaces using the same vrid but with different ip
addresses, or is this vrid unique. If the former is true then why
would one use a vrid, when the ip addresses could act as the 
primary key. using the vrid as a primary key would improve VRRP
performance drastically.

Thanks,
Vivek.

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From: Acee Lindem <[email-masked]>
Date: Wed, 29 Jul 1998 09:46:31 -0400

Vivek Menezes wrote:
> addresses, or is this vrid unique. 

Vivek,

Since the VRID is used to derive the virtual MAC address each instance 
of VRRP (master and one or more backups) should be unique on a LAN
segment. 

> If the former is true then why
> primary key. 

You may want to define multiple VRIDs with the same set of addresses
to load-share and still allow the Virtual Routers to back each
other up. Isn't this clear in the RFC? 

> using the vrid as a primary key would improve VRRP
> performance drastically.

When you consider the total number of instructions to process a 
protocol packet and that most LAN segments with VRRP active will
only be using 1 or 2 VRIDs I don't believe making VRIDs unique 
across a group of routers running VRRP would offer a great 
improvement. 

-- 
Acee

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From: Vivek Menezes <[email-masked]>
Date: Wed, 29 Jul 1998 10:56:38 -0700 (PDT)

> > addresses, or is this vrid unique. 

I'm sorry but I later found out that the unique key for a virtual router
is both the VRID and the set of IP addresses. (Its in VRRP overview)
 
> other up. Isn't this clear in the RFC? 

I dont think you should do this . An arp request for an ip address would
reveal 2 or more mac address replies. Load balancing is achieved by
dividing the hosts into groups using different IP addresses as their
default routes.

Vivek.

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From: Acee Lindem <[email-masked]>
Date: Wed, 29 Jul 1998 14:20:34 -0400

> dividing the hosts into groups using different IP addresses as their

This is exactly how you do it with VRRP. For simplicity, let's assume
2 groups with 2 default gateways. You'd then allocate 2 VRIDs and make
each gateway the master wrt to one VRID and a backup wrt the other. 

-- 
Acee