ezs | Nothing of Any Quincyquonce

Postfix, IPv6 and non-delivery

by ezs | Aug 6, 2012 | Uncategorized

Interesting issue this week with Postfix and IPv6. The webserver was resolving MX records as usual for delivery of blog notification – and also looking up AAAA records for delivery via SMTP over IPv6. Without a functioning route from home to the far end these were obviously failing and not retrying with the (routable) IPv4.

The fix was to force Postfix to only use IPv4 – there’s a great readme on this.

/etc/postfix/main.cf:
    # You must stop/start Postfix after changing this parameter.
    inet_protocols = ipv4       (DEFAULT: enable IPv4 only)

Ekahau sitemapper

by ezs | Jul 11, 2012 | Uncategorized

One of the major frustrations with wireless networking is the proliferation of noise from neighbours.

When I got my first Wifi router – back in 1999 – there was practically zero interference. From our house in Nottingham I got a whopping 11Mb/s and mine was the only network in sight.

I’m writing this sitting on the deck working. My laptop can see over 30 different wifi networks. Some are secured; most are not. I’ve been offering to secure neighbours networks to prevent “driveby surfing” and the associated risks.

It seems as if the vast majority of networks are set to use channel 1 – the very few routers set to “auto” or “channel switch” are bouncing between 4 and 6.

I’ve been using Ekahau Heatmapper for a while to walk the house and deck and check the signals. Two benefits – I can spot “who’s new” and what they are broadcasting on. Secondly I can tweak the settings for the two networks at home and make sure they are performing optimally.