[ovs-dev] [PATCH] FAQ: Explain why allowing only unicast traffic breaks IP connectivity.
Ben Pfaff
blp at nicira.com
Wed Sep 25 20:14:49 UTC 2013
Signed-off-by: Ben Pfaff <blp at nicira.com>
---
FAQ | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/FAQ b/FAQ
index 5744d5a..91eb870 100644
--- a/FAQ
+++ b/FAQ
@@ -1299,6 +1299,26 @@ A: Yes, OpenFlow requires a switch to ignore attempts to send a packet
2,3,4,5,6,\
pop:NXM_OF_IN_PORT[]
+Q: My bridge br0 has a host with MAC address 54:00:00:00:00:01 on port
+ 1 and a host with MAC address 54:00:00:00:00:02 on port 2. I set
+ up flows to forward only traffic destined to the other host and
+ drop other traffic, like this:
+
+ priority=5,in_port=1,dl_dst=54:00:00:00:00:02,actions=2
+ priority=5,in_port=2,dl_dst=54:00:00:00:00:01,actions=1
+ priority=0,actions=drop
+
+ But it doesn't work--I don't get any connectivity when I do this.
+ Why?
+
+A: Hosts broadcast the ARP packets needed to establish IP connectivity
+ on an Ethernet network. Your flows only allow unicast packets, so
+ the hosts can never establish connectivity. To solve the probelm,
+ you minimally need to add flows to allow ARP. But it's probably
+ better to add flows to allow all multicast and broadcast traffic:
+
+ priority=5,in_port=1,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00,actions=2
+ priority=5,in_port=2,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00,actions=1
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