Thousands of hosts on a gigabit LAN, maybe not

Karl Auer kauer at
Sat May 9 22:33:54 UTC 2015

On Sat, 2015-05-09 at 17:06 -0400, Lamar Owen wrote:
> The effective limit on subnet size would be of course broadcast 
> overhead; 1,000 nodes on a /22 would likely be painfully slow due to 
> broadcast overhead alone.

Would be interesting to see how IPv6 performed, since is one of the
things it was supposed to be able to deliver - massively scalable links
(equivalent to an IPv4 broadcast domain) via massively reduced protocol
chatter (IPv6 multicast groups vs IPv4 broadcast), plus fully automated
L3 address assignment.

IPv4 ARP, for example, hits every on-subnet neighbour; the IPv6
equivalent uses multicast to hit only those neighbours that happen to
share the same 24 low-end L3 address bits as the desired target - a
statistically much smaller subset of on-link neighbours, and in "normal"
subnets typically only one host. Only chatter that really should go to
all hosts does so - such as router advertisements.

Regards, K.

Karl Auer (kauer at

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