From 6a8313068549c739d21e3f6ed06b086265886d89 Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Mon, 30 Jan 2017 18:14:57 +0000
Subject: [PATCH] Document multicast behaviour of weave-npc

---
 site/kube-addon.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/site/kube-addon.md b/site/kube-addon.md
index 7dc08df4..284270b7 100644
--- a/site/kube-addon.md
+++ b/site/kube-addon.md
@@ -79,6 +79,13 @@ Kubernetes see the
 and the [NetworkPolicy API object
 definition](http://kubernetes.io/docs/api-reference/extensions/v1beta1/definitions/#_v1beta1_networkpolicy).
 
+**Note:** as of version 1.9 of Weave Net, the Network Policy
+  Controller allows all multicast traffic. Since a single multicast
+  address may be used by multiple pods, we cannot implement rules to
+  isolate them individually.  You can turn this behaviour off (block
+  all multicast traffic) by adding `--allow-mcast` as an argument to
+  `weave-npc` in the YAML configuration.
+
 ###<a name="blocked-connections"></a> Troubleshooting Blocked Connections
 
 If you suspect that legitimate traffic is being blocked by the Weave Network Policy Controller, the first thing to do is check the `weave-npc` container's logs.