[ovs-discuss] Difference between set_field:x.x.x.x->nw_dst and mod_nw_dst

Ben Pfaff blp at ovn.org
Sun Jul 17 22:34:11 UTC 2016


On Sun, Jul 17, 2016 at 11:07:17PM +0100, D3c3 Balus wrote:
> I’d like to understand the difference between these 2 actions:  actions=set_field:1.1.1.1->nw_dst    vs.   actions=mod_nw_dst:1.1.1.1 ?
> In my understanding, the end result is the same, but what would be different ?
> 
> Yes, I have read about the differences between set_field:value and load:value  (not interested in this)

The differences are all in technicalities.

mod_nw_dst is an OpenFlow 1.0 and 1.1 action.  set_field is a more
general-purpose OpenFlow 1.2 and later action (and also an Open vSwitch
extension to OF1.0 and OF1.1).

In OpenFlow 1.0, mod_nw_dst doesn't imply any prerequisite on the flow
match; that is, it can be used in a flow that does not match on an
Ethernet type of 0x800.  In OpenFlow 1.1 and later, it does require such
a flow match, and the same is true of set_field regardless of OpenFlow
version.



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