Thousands of hosts on a gigabit LAN, maybe not

Fri May 8 19:19:43 UTC 2015

On Fri, May 8, 2015 at 2:53 PM, John Levine <johnl at iecc.com> wrote:
> 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

consider the pain of also ipv6's link-local gamery.
look at the nvo3 WG and it's predecessor (which shouldn't have really
existed anyway, but whatever, and apparently my mind helped me forget
about the pain involved with this wg)

I think 'why one lan' ? why not just small (/26 or /24 max?) subnet
sizes... or do it all in v6 on /64's with 1/rack or 1/~200 hosts.