anchor.diff:  
   === Source MAC-address mapping using a file 
   
  -Extending the source MAC-address  replacment capability. 
  +Extending the source MAC-address  replacment capability.
   It is possible to have a mapping betwean IPv4->MAC using the new `--mac` CLI switch  
   file format is YAML.
   
  
positive.code: 
  === NAT support 
  
  TRex can learn dynamic NAT/PAT translation. To enable this feature add `--learn-mode <val>` to the command line.
  
  *mode 1:*::
  
  In this mode, It is done by embedding NAT info into the ACK of the first TCP SYN.
  In this mode, there is a limitation that UDP templates with two directions won't be supported (e.g. DNS). 
  The reason for this feature is that Cisco ASA drops any packet with ipv4 option.
  
  *mode 2:*::
  
  In this mode, it is done by adding an IPv4 option header with TRex info (8 bytes long 0x10 id) to the first packet of the flow. 
  
  ==== Examples
  
  
negative.code: 
  === TRex with ASA 5585
  
  Running TRex aginst ASA 5585 has some limitations:
  
  * There is a need to disable TCP sequence randomization in ASA, using the command `set connection random-sequence-number disable`
  * ASA can't forward ipv4 options, so there is a need to use --learn-mode 1 in case of NAT. In this mode, bidirectional UDP flows are not supported.
  * Latency should be tested using ICMP with `--l-pkt-mode 2`
  
  ====  ASA 5585 sample configuration
  