[ovs-dev] [PATCH] FAQ: Explain that the order of actions is significant.
Ben Pfaff
blp at ovn.org
Fri Jun 3 16:10:15 UTC 2016
I've seen users make this error several times. This FAQ will provide a
useful answer to pass along.
Signed-off-by: Ben Pfaff <blp at ovn.org>
---
FAQ.md | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/FAQ.md b/FAQ.md
index 5e95ccc..df6f225 100644
--- a/FAQ.md
+++ b/FAQ.md
@@ -2012,6 +2012,23 @@ A: In Open vSwitch 2.3 and earlier, Open vSwitch used the destination
vSwitch source tree. (OpenFlow 1.5 support in Open vSwitch is still
experimental.)
+### Q: I added a flow to accept packets on VLAN 123 and output them on
+ VLAN 456, like so:
+
+ ovs-ofctl add-flow br0 dl_vlan=123,actions=output:1,mod_vlan_vid:456
+
+ but the packets are actually being output in VLAN 123. Why?
+
+A: OpenFlow actions are executed in the order specified. Thus, the
+ actions above first output the packet, then change its VLAN. Since
+ the output occurs before changing the VLAN, the change in VLAN will
+ have no visible effect.
+
+ To solve this and similar problems, order actions so that changes
+ to headers happen before output, e.g.:
+
+ ovs-ofctl add-flow br0 dl_vlan=123,actions=mod_vlan_vid:456,output:1
+
Development
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--
2.1.3
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