Category Archives: Networking

Reuse a spare BT Home Hub as a Wireless Access Point

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This article was rewritten and updated on 9th April 2017.

BT is a popular Internet service provider in the UK.  BT subscribers receive a free router called the “BT Home Hub“.  A new model of Home Hub is launched every few years, and as BT never takes the old ones back, many people have an old Hub tucked away somewhere, gathering dust.

This post explains how to convert an old BT Home Hub 5.0 or Home Hub 4.0 into a second wireless access point (“AP”) on your network, strengthening and extending the wireless signal around your home or office.  Although the details are for those routers, the basic procedure works for other BT and perhaps non-BT routers.  In particular, notes have been included for the BT Home Hub 3.0 and the now ancient Home Hub 1.0 – these are indented and written in italics.  Many users have also had success in reusing Home Hub models 2.0 and 6.0 (BT’s latest router, also known as the Smart Hub). Continue reading →

BT Home Hub Cannot Access SSL Website

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This article explains why the BT Home Hub routers appears unable to access SSL/TLS (https) websites on your internal home network.  It may interest users in the UK, where the Home Hub is a popular router/ADSL modem.

Hosting your own website(s) at home is pretty easy these days.  You have a small server running Apache, and configure your router to forward port 80 to it.  For SSL sites, you forward port 443.  That’s about it. Continue reading →

File Serving: Sheevaplug vs Pi vs WDTV vs Linkstation vs Home Hub 3

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In need of some network storage in the home ? Well, you could go off and buy a proper NAS unit, offering RAID, several Tb of storage, fast access speeds and so on. On the other hand, you might have something lying round the house that will do. It won’t be as good as a proper NAS, but it might just be good enough. Continue reading →

Mounting BT Home Hub 3 USB on WD TV Live

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This post may be of interest to UK users who own both a BT Home Hub 3 router and a WD TV Live media streamer. Both are Linux based systems, but getting one to work with the other can be a bit of a challenge.

The USB port on the back of the Home Hub 3 can be used to share storage over the network. Plug in a disk or memory stick, and it is automatically shared out as a windows share. Using a large capacity memory stick offers the possibility of NAS like, always-on access to your media files from any connected device. Low power consumption too. This post explains how access the USB connected drive from the WD TV Live. Continue reading →

Using Tcpdump to See Background DNS Requests

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This post explains how to use tcpdump on Linux to detect and investigate DNS requests. One of our Red Hat client systems was making requests to an old DNS server, even though it had been adjusted, through a change to/etc/resolv.conf, to point to a new one.

Requests to the old server were identified as follows.

[root@pluto root]# tcpdump -i eth0 -l -vvv dst host 192.168.1.103 and dst port 53
(...waited 15 mins or so...)
tcpdump: listening on eth0
16:38:18.019703 pluto.mycompany.com.41783 > olddnsbox.mycompany.com: [bad udp cksum 48f5!]  21331+ A? somebox.mycompany.com. (42) (DF) (ttl 64, id 48623, len 70)
16:38:18.033461 pluto.mycompany.com.41783 > olddnsbox.mycompany.com: [bad udp cksum 5919!]  12099+ A? somebox.mycompany.com. (42) (DF) (ttl 64, id 48625, len 70)

192.168.1.103 is the ip address of the old DNS server. Tcpdump shows network packets sent to the standard DNS port (53) at that IP address. Requests were few so I had to wait 15 or 20 minutes to capture the above.

The client was last rebooted a year ago, many months before /etc/resolv.conf was last edited. Tcpdump shows that some application is still querying the old server. The fix was to reboot the client, restarting the erroneous application and stopping the outdated requests.

Sendmail Authentication for Local Mail Delivery

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These days, service providers like British Telecom have tightened up their requirements on email delivery. Most ISPs now accept email only from servers that can authenticate through SMTP. Sendmail has authentication built in, allowing administrators to use an “authinfo” file, for example. The server then authenticates every time it sends mail out to the ISP.

That’s great for reducing spam. But it can have a side-effect of killing local mail on the server. Here is an recent example from Debian Squeeze. The authentication features that allowed this server to successfully send mail through the ISP were preventing local mail from working: Continue reading →

Copying Directories with SSH

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Copying data is something every administrator does.  A single file or directory file can be copied with a single command.  Moving information from one system to another needs a bit more work, but it needn’t be a pain.

The ssh command can be used to copy data from one Unix system to another.    Here is an example for HP-UX, but it works on Linux too.  A directory, called /var/opt/ignite, is copied from the system “pluto” to another machine called “jupiter”. Continue reading →