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Spirent TestCenter: Why is STC XORing the destination MAC with the MAC from the ARP?

  • Spirent TestCenter.
If we have a configuration were with a bound stream block going from Device 1 to Device 2; let's suppose assume we have the configuration below:
  • Destination MAC address: 20:01:01:00:01:00
  • Modifier: 00:00:00:00:00:01
  • Mask: 00:00:FF:FF:FF:FF.
  • Gateway IP address:
  • When we send the ARP, the reply shows the MAC address: 20:01:01:00:01:00.
Since we have two different sources (destination ARP and the Modifier) updating the same field (MAC address), Spirent TestCenter is mixing them, and that’s why it XOR’ing it.  So this is expected behavior.
Below are some options you can try to avoid the MAC to be XORed.
  •  If you need to generate traffic toward multiple MAC addresses without ARPing, please configure the actual MAC address in the modifier and disable the “Resolve Destination MAC Address“ option.
  • If you’re using an FX/MX module, you can add a stream modifier for the destination IP address, and then each stream will get the ARP resolved and use its own MAC address.
  • If you’re using a DX/PX module, you can create separate stream blocks.
  • If you need to resolve the MAC address as the modifier's initial value, you will need to reconfigure the stream block

Product : Spirent TestCenter