Subject: [VRRP] Queries regarding draft-ietf-vrrp-unified-spec-02

From: "Suraj R" <[email-masked]>
Date: Thu, 15 Jan 2009 22:36:30 +0800

Hi,

I have some queries in "draft-ietf-vrrp-unified-spec-02", Please help me to
clarify the same.

1) Question :  Virtual router can be configured with one or more IPv6
address. I would like to know the application scenario, why multiple IPv6
virtual address are required in virtual address.

6.1.  Parameters per Virtual Router
IPv6_Addresses             One or more IPv6 addresses associated with
                           this virtual router.  Configured item.  No
                           default.  The first address must be the Link-
                           Local address associated with the virtual
                           router.
2) Question: When the Master router goes down and before it comes
up(restarts), if any other node in the network configures the same IPv6
address of Master router and backup router is not available, then there will
be a address
conflict in the network. This scnario will happen when DAD is not
performed(Owner address) by Master when it restarts.

8.2.2.  ND Neighbor Solicitation
   Note that on a restarting Master router where the VRRP protected
   address is the interface address, (that is, priority 255) duplicate
   address detection (DAD) may fail, as the Backup router may answer
   that it owns the address.  One solution is to not run DAD in this
   case.

3) Question: The draft discuss about how to fill the source address when
sending out a Redirect message by a virtual router.

But I would like to know what is the actual scnario where Redirct is used
when hosts are connected
to virtual routers.

8.2.1.  ICMPv6 Redirects

   The IPv6 source address of an ICMPv6 redirect should be the address
   the end host used when making its next hop routing decision.  If a
   VRRP router is acting as Master for virtual router(s) containing
   addresses it does not own, then it must determine which virtual
   router the packet was sent to when selecting the redirect source
   address.  A method to deduce the virtual router used is to examine
   the destination MAC address in the packet that triggered the
   redirect.

4) The following is my understanding from the Draft, Please correct if it is
wrong
This problem will happen when accept mode flag is disbaled(all host route
associated with virtual address
will get deleted), so when a packet is received for a virtual address which
is not address owner, the virtual
router should drop the packet and should not forward it.

8.3.1.  Potential Forwarding Loop

   A VRRP router SHOULD not forward packets addressed to the IPvX
   Address it becomes Master for if it is not the owner.  Forwarding
   these packets would result in unnecessary traffic.  Also in the case
   of LANs that receive packets they transmit (e.g., token ring) this
   can result in a forwarding loop that is only terminated when the IPvX
   TTL expires.

   One such mechanism for VRRP routers is to add/delete a reject host
   route for each adopted IPvX address when transitioning to/from MASTER
   state.
The RFC states that the VRRP advertisement can have multiple virtual IPv6
addresses. How are these addresses used by the VRRP router & host device ?

Best regards,

*Suraj** R *
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