Subject: @VRRP-Critical Qustions for implementation.

From: 유용수 <[email-masked]>
Date: Mon, 26 Jun 2000 19:58:11 +0900

Hello,
I have some questions. Some of these are meaningful I think. 
Sorry for poor english in advance.
And hope many people comment about this.

Questions are as follows.
------------------------------------------------------------
(Q.1) When one can consider another was failed? 
       (What condition makes it impossible to send vrrp advertisment-msg?)

Assume two router runnnig vrrp.
Each router has a connection to a WAN.
When one consider another was failed? 
 I think as follows.
 - when physical line disconnected
 - when router was down (->power off)
 - when router's software was down or crashed (->power on)
 Are these condition enough?
 Assume one router's wan connection is failed(-out of use, whether connected or not) 
 - we have to apply this condition to vrrp operation or not?
          Is this out of vrrp range or not?
------------------------------------------------------------
(Q.2) When is it useful especially? 

Is there someone who has specific "vrrp sample configuration" which 
 applied to real network or expected to be applied?
(I searched but could't find . I wonder about this very much)
------------------------------------------------------------
(Q.3) Running vrrp on multiple interface

Let's assume a router have many interfaces,
Should the router be capable of running vrrp on multiple interface simultaneously?
This capability is needed?
------------------------------------------------------------
(Q.4) OSPF for fast fail-over in the WAN

Even if one runs vrrp between routers which capable of fast fail-detection ,
I think " real fail-over " is dependant on routing protocol in the wan.
(because routing protocol such as rip convergence slowly
         so can't reroute retun-path fastly in short time.)
Right? 
------------------------------------------------------------

Thanks,
Yongsu Yu

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From: Hamayon Mujeeb <[email-masked]>
Date: Mon, 26 Jun 2000 10:47:59 -0400 (EDT)

If you are asking about "when Backup should consider the Master to 
be down ?" ...  When the Backup does not recieve an advertisement from 
the Master for Master_Down_Time seconds, it should consider the 
Master to be Down. 
The reason is not important. It could be anything stopping 
the Master to function properly and send out the periodic VRRP 
advertisement.

If you are asking about "when the Master should consider itself to
be down (and send a zero-priority advertisement) ? ... It is only
when the corresponding IP interface goes down, and the Master is
still able to send traffic on the wire. (In cases where power
fails, or connection is down or physical line breaks, the Master 
would not be able to send out anything anyway ...)

Yes. There should be no restriction ...

VRRP is more targeted towards networks which have hosts that are NOT 
running routing protocols. These hosts have default routes to the
gateways in the local LANs, and hence loose connectivity to outside
world once the default gateway is down. VRRP solves this problem 
by allowing multiple routers in the LAN taking responsibilty for
the default gateway address(es) without the host knowing about
that.

I don't see a great advantage of running VRRP and a routing 
protocol at the same time ... maybe somebody can enlighten me.
(Although the routers run routing protocols among themselves, 
it is the hosts that do not run routing protocols, that benefit 
from VRRP.)

Hamayon Mujeeb
Nortel Networks