title: How to isolate trafic for two netifs in LwIP
body: <p>I'm setting up an STM32H7 board with two networks interface ports (netifs).
  Both are using the LwIP stack. The MCU is not running FreeRTOS (NOSYS), so I'm using RAW API's (callbacks) for LwIP.
  The two ports have different MAC and IP addresses. Now I would like run a TCP server on one port and a TCP client on the other. So I need to separate the traffic for each port.
  If I want to use them independent do I need two different instances of LwIP? I use Atollic TrueStudio and C as programming language, not C++.
  How can I best do this?</p>