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TOPIC: Unicast ARP

Unicast ARP 9 years 10 months ago #30110

I recently was looking at some packet captures on my network when I realized something that seemed a bit strange to me. There was Linux machines (namely Ubuntu) that were sending ARP requests for machines and the frames had a destination MAC address of the actual machine. I checked the ARP cache on these machines and they of course had the correct MAC address in it's cache.

I was always taught and under the impression that ARP requests were always broadcast (destination FF:FF:FF:FF:FF:FF) It is as if since the machines had it's MAC address cached, it would not broadcast these frames unless the ARP cache was cleared. I verified this by deleting the ARP entry, and I viewed the first ARP request as broadcast, and subsequent ones unicast.

I guess this makes sense to reduce broadcast traffic, and it may be something that only Linux incorporates. Does anyone know the source of this behavior?

Re: Unicast ARP 9 years 10 months ago #30112

  • S0lo
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Interesting, It indeed seams that some implementation of linux do that, although I'm not sure here.
Studying CCNP...

Ammar Muqaddas
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Re: Unicast ARP 9 years 9 months ago #30173

Anyone else know anything about this? Is this normal?
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