Thousands of hosts on a gigabit LAN, maybe not

Brian R briansupport at
Fri May 8 20:16:03 UTC 2015

Agree with many of the other comments.  Smaller subnets (the /23 suggestion sounds good) with L3 between the subnets.
<off topic>
The first thing that came to mind was "Bitcoin farm!" then "Ask Bitmaintech" and then "I'd be more worried about the number of fans and A/C units".
 </off topic>
> Date: Fri, 8 May 2015 18:53:03 +0000
> From: johnl at
> To: nanog at
> Subject: Thousands of hosts on a gigabit LAN, maybe not
> Some people I know (yes really) are building a system that will have
> several thousand little computers in some racks.  Each of the
> computers runs Linux and has a gigabit ethernet interface.  It occurs
> to me that it is unlikely that I can buy an ethernet switch with
> thousands of ports, and even if I could, would I want a Linux system
> to have 10,000 entries or more in its ARP table.
> Most of the traffic will be from one node to another, with
> considerably less to the outside.  Physical distance shouldn't be a
> problem since everything's in the same room, maybe the same rack.
> What's the rule of thumb for number of hosts per switch, cascaded
> switches vs. routers, and whatever else one needs to design a dense
> network like this?  TIA
> R's,
> John

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