Re: [VRRP] [tsv-dir] Arps and grat arps was (RE: tsv-dir review ofdraft-ietf-vrrp-unified-spec-02.txt)

[Joe Touch <touch at ISI.EDU>]

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Mark Handley wrote:
> Sorry - my confusion - the text does say ARP *request*, but I was
> thinking of ARP responses.  You are of course correct.
> 
>  - Mark
> 
> On Tue, Nov 4, 2008 at 9:04 PM, don provan <dprovan at bivio.net
> <mailto:dprovan at bivio.net>> wrote:
> 
>     Do they sniff MAC addresses in ARP packets? I didn't know that
>     was legal.
>      
>     The source MAC address in the ARP packet's MAC header must always
>     be the physical MAC address of the system, of course, never the
>     VR MAC address. I've only ever heard of switches learning based
>     on the source MAC address *in* the MAC header. Am I about to have
>     a learning experience?

Not only switches, FWIW, but end hosts sniff too. This caused a problem
a few IETFs back (as someone on this list may recall).

Joe

>     -don
> 
>         -----Original Message-----
>         *From:* mark.j.handley at gmail.com
>         <mailto:mark.j.handley at gmail.com>
>         [mailto:mark.j.handley at gmail.com
>         <mailto:mark.j.handley at gmail.com>]*On Behalf Of *Mark Handley
>         *Sent:* Tuesday, November 04, 2008 12:36 PM
>         *To:* don provan
>         *Cc:* Stephen Nadas; TSV Dir; vrrp
>         *Subject:* Re: [VRRP] Arps and grat arps was (RE: tsv-dir review
>         ofdraft-ietf-vrrp-unified-spec-02.txt)
> 
> 
> 
>         On Tue, Nov 4, 2008 at 7:27 PM, don provan <dprovan at bivio.net
>         <mailto:dprovan at bivio.net>> wrote:
> 
> 
>             But it doesn't really matter: all routers *can* send gratuitous
>             ARP messages for the VR. The VR ARP information is constant: it
>             does not change when the VRRP master changes. No black hole
>             would
>             be created: all the entries map the VR IP address to the VR MAC
>             address. The current master is the node that receives all
>             packets
>             sent to the VR MAC address no matter what node actually
>             distributed
>             the VR ARP mapping.
> 
> 
>         Won't you blackhole the traffic if you do this on a LAN composed
>         of MAC-learning switches?
> 
>          - Mark
> 
> 
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