From 51f56211dbd96637f6f8e0c5f5b5a4043aa28368 Mon Sep 17 00:00:00 2001 From: Brian E Carpenter Date: Sat, 20 Apr 2024 15:46:20 +1200 Subject: [PATCH] Add advice on subnet size --- 5. Network Design/5. Network Design.md | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/5. Network Design/5. Network Design.md b/5. Network Design/5. Network Design.md index b5fcada..9614366 100644 --- a/5. Network Design/5. Network Design.md +++ b/5. Network Design/5. Network Design.md @@ -41,6 +41,16 @@ approach will vary. The NOC must be designed from the start based on IPv6, with the ability to manage IPv4 as a service. +- A specific difference between a retrofit design and a greenfield design + is that an existing IPv4 network almost inevitably has subnets limited + to 256 or fewer hosts, often as few as 64. Since the normal subnet + prefix in IPv6 is a /64, there is no such limitation in a greenfield + deployment of IPv6. However, for + practical reasons such as the rate of link-local multicasts, very large + subnets should be avoided. As noted elswehere + \[[2. Address resolution](../2.%20IPv6%20Basic%20Technology/Address%20resolution.md)\] + this applies particularly to wireless networks. + This chapter continues with a discussion of address planning, inevitably combined with subnet design.