Thousands of hosts on a gigabit LAN, maybe not

Jerry J. Anderson, CCIE #5000 jerry.anderson at
Sat May 9 21:14:17 UTC 2015

> 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

Brocade's Virtual Cluster Switching (VCS) fabric on their VDX switches is a good solution for large, flat data center networks like
this.  It's based on TRILL, so no STP or tree structure are required.  All ports are live, as is all inter-switch bandwidth.  Cisco
has a similar solution, as do other vendors.

Thank you,

Jerry J. Anderson, CCIE #5000
Member, Anderson Consulting, LLC
800 Ridgeview Ave, Broomfield, CO  80020-6618
Office: 650-523-2132     Mobile: 773-793-7717

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