arp nf and load balancer tutorial

[andreaseno]

Bug Report

Current Behavior
sometimes the tutorial does not work because the arp nf is not responding. The commands in the document are incorrect if the client side is port 1 and the server side is port 0. Iperf reports the error: "connect failed: Operation now in progress"

Expected behavior/code
2 options:

1. either the arp nf should work correctly regardless of order of the ips
2. or the pdf needs to be changed to be able to handle either case.

Steps to reproduce
This happens if the client side is port 1 and the server side is port 0. Works correctly in inverse case.

Environment
tested on cloudlab c220g2 nodes with 2 backend servers

Possible Solution
make arp nf respond to requests on any port (not just the one that matches the ip)