Is there any data on packet duplication?

Sabri Berisha sabri at cluecentral.net
Tue Jun 23 06:31:28 UTC 2020


----- On Jun 22, 2020, at 11:21 PM, Saku Ytti saku at ytti.fi wrote:

Hi Saku,

> On Tue, 23 Jun 2020 at 09:15, Sabri Berisha <sabri at cluecentral.net> wrote:
> 
>> Yeah, except that unless you use static ARP entries, I can't come up
>> with a plausible scenario in which this would happen for NTP. Assuming
>> we're talking about a non-local NTP server, S3 will not send an NTP
>> packet without first sending an ARP. Yes, your ARP will be flooded,
>> but your NTP packet won't be transmitted until there is an ARP reply.
>> By that time MACs have been learned, and the NTP packet will not be
>> considered BUM traffic, right?
> 
> The plausible scenario is the one I explained. The crucial detail is
> MAC timeout (catalyst 300s) being shorter than ARP timeout (cisco 4h).
> So the device generating the packet knows the MAC address, the L2 does
> not.

Aaah yes, fair point! Thanks $deity for default timers that make no sense.

Thanks,

Sabri


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