From 26c1bcf866dbebba5a3ed89c63d2fb8c7f46fb2b Mon Sep 17 00:00:00 2001 From: Matthias Radestock Date: Wed, 8 Jul 2015 16:51:25 +0100 Subject: [PATCH] clarify role of IP allocator range Part of #1035. --- site/ipam.md | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/site/ipam.md b/site/ipam.md index 295bbf93..09f2a2b3 100644 --- a/site/ipam.md +++ b/site/ipam.md @@ -94,6 +94,14 @@ range. This can be overridden with the `-iprange` option, e.g. and must be the same on every host. +> The specified range is for *exclusive* use by the IP allocator. In +> particular, when starting containers with manually assigned IP +> addresses, these must be outside the IP allocator's range. If, in +> our example, you subsequently executed `docker run -e +> WEAVE_CIDR=10.2.3.1/24 -ti ubuntu`, the IP allocator might assign +> the same address to another container, which will break IP routing +> for the containers sharing an address. + The range parameter is written in [CIDR notation](http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing) - in this example "/16" means the first 16 bits of the address form the @@ -108,14 +116,6 @@ the rest (a partition), they can continue to work with the address ranges they had before isolation, and can subsequently be re-connected to the rest of the network without any conflicts arising. -Once you have given a range of addresses to the IP allocator, you must -not use any addresses in that range for anything else. If, in our -example, you subsequently executed `docker run -e WEAVE_CIDR=10.2.3.1/24 -ti ubuntu`, -you run the risk that the IP allocator will assign the same address to -another container, which will make network traffic delivery -intermittent or non-existent for the containers that share the same IP -address. - ## Automatic allocation across multiple subnets When