Subject: Why Virtual MACs....?

From: Badri Srinivasan S <[email-masked]>
Date: Thu, 05 Apr 2001 12:08:12 +0530

Hi:

another doubt down the line...

1. Why is it necessary that the source MAC addr of the VRRP
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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

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From: Vikram <[email-masked]>
Date: Thu, 5 Apr 2001 07:18:54 -0700 (PDT)

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

> if it can be implemented like this , what is the purpose of Virtual

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

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