gistfile1.py

#!/usr/bin/env python

import re

totals = {'packets': 0, 'traffic': 0}

with open('traffic.log', 'r') as fp:
    content = fp.read()
    lines = content.split('\n')

    for line in lines:
        if 'External' not in line:
            continue

        matches = re.search('.*(\d+\.\d+) packets/300s.*(\d+) MBit.*', line)

        if not matches:
            continue

        groups = matches.groups()
        packets = float(groups[0])
        traffic  = float(groups[1])

        totals['packets'] += packets
        totals['traffic'] += traffic

    print 'Totals'
    print '%s pkts/s, %s Mb/s' % (totals['packets'], totals['traffic'])