doc: clarify usage of testpmd MAC forward mode

Explain default testpmd behavior in mac fwd mode to remove
amiguity/confusion regarding user's ability to specify Ethernet
addresses.

Signed-off-by: Mark Kavanagh <mark.b.kavanagh@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>

diff --git a/doc/guides/testpmd_app_ug/testpmd_funcs.rst b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
index 6ea285a..5e47633 100644 (file)
--- a/doc/guides/testpmd_app_ug/testpmd_funcs.rst
+++ b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
@@ -270,6 +270,9 @@ The available information categories are:
   This is the default mode.
 
 * ``mac``: Changes the source and the destination Ethernet addresses of packets before forwarding them.
+  Default application behaviour is to set source Ethernet address to that of the transmitting interface, and destination
+  address to a dummy value (set during init). The user may specify a target destination Ethernet address via the 'eth-peer' or
+  'eth-peer-configfile' command-line options. It is not currently possible to specify a specific source Ethernet address.
 
 * ``macswap``: MAC swap forwarding mode.
   Swaps the source and the destination Ethernet addresses of packets before forwarding them.