Subject: RE: Why Virtual MACs....?

From: "Fernandes, Flavio" <[email-masked]>
Date: Thu, 5 Apr 2001 10:49:43 -0400

Another way of "looking" at what VRRP tries to address via Virtual Macs:

As VRRP was defined, a concern existed (and still exists) in moving IP
address
ownership around. 

That is so because management stations normally use IPs as indexes for
tables in
their monitoring scheme. It is a bad trouble to have stations confused about
"who" the
IP owner really is for the purposes of walking SNMP tables, ping, telnet,
etc...

Thus, moving the ownership of Mac addresses was the solution found (virtual
Macs to be
more exact. :)).

-- flavio

-----Original Message-----
From: Vikram [mailto:[email-masked]]
Sent: Thursday, April 05, 2001 10:19 AM
To: Badri Srinivasan S; VRRP
Subject: Re: Why Virtual MACs....?

The moot purpose of the virtual mac is to allow the learning bridges to
know which lan segment the virtual router is in other than letting the
failover to be transparent(and fast) to endhosts.

If I missed anything please fill me in.

tks,

vikram

--- Badri Srinivasan S <[email-masked]> wrote:
> Hi:
> 
> another doubt down the line...
> 
> 1. Why is it necessary that the source MAC addr of the VRRP
> Advertisements
> must me set to the Virtual MAC addr...i really dont understand the
> real
> purpose of virtual MACs...
> 
> Can we solve the prob without using vMACs but only virtual IPs in the
> following way..
> 
> -->Whenever a VRRP router becomes a master, add the virtual IP
> address
> to the master's ethernet by doing a IP aliasing..
> -->Then let the Master do a gratutious ARP for the virtual IP addr
> ----
> real MAC combination so that the hosts update their ARP cache with
> this.
> 
> -->so when the host wants to send a pckt to the virtual IP, its wiil
> look into its ARP cache & get the real MAC of the Master..
> or else , it can make  an ARP req  for the Virtual IP addr , and the
> Master replies with its real MAC addr & not any vMAC..
> 
> so the pckts ultimately reach the Master...
> When the Master goes to the backup state it removes the virtual IP
> alias..
> The new Master performs the same steps whenit starts just as above..
> i.e --> Do an IP alias for the virtual IP
>     --> do a gratutious ARP with virtual IP --- the new Masters real
> MAC...
> 
> 
> if it can be implemented like this , what is the purpose of Virtual
> MAC..
> 
> please reply..
> 
> thanks & Regards,
> Badri
> 

=====
----
NO sense being pessimistic. It wouldnt work anyway

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