OpenWRT

The things you do on a rainy Saturday when you really shouldn’t just go to the pub…

I’ve had a TP-Link WR-2543 router for some time now, since I discovered the Cisco I had before was effectively throttling my connection. For the cost (some time ago), it’s a pretty good device- but it’s getting on, the firmware’s no longer updated (a continual problem with embedded systems), and well…hell. I’ll stop making excuses. I was bored and had another TP-Link router lying about for a bit of experimentation, and haven’t done much at-home tech mucking about for a good while.

OpenWRT, DD-WRT, and others are firmware replacements for domestic routers, born from the famous WRT54G having firmware developed from GPL code (and therefore being required to be made public). They offer more up-to-date software, more facilities, and, as is often the case with anything open-source, a price to pay for the power and tweakability.

As it was, my test router, a WR740N, was a breeze. Log in to the OEM interface, apply the file, job done: a nice web interface and a shell interface over SSH, and everything working. This made me brave, so on went the image to the 2543.

I didn’t brick it :-). In fact, all looked good. The wiki page for this device suggested no major problems, and it was all OK, until I came to connect to the Internet: I just couldn’t get the WAN interface to come up, and in fact, it had a MAC address of 00:00:00:00:00:00. In other words, no interface.

There follows an object lesson in open-source software. RTFM. However, TFM was a bit light for the 2543, so I had to think a little laterally- the experience with the 740 had suggested that the WAN port would appear as a seperate interface, but all I had was 2 sub-interfaces. Poking around the Wiki told me something I hadn’t realised: many of these devices are implemented in 3 blocks, the wifi, the CPU/Memory/Flash, and a single ethernet switch. The WAN interface is just a subinterface, with VLAN tagging to seperate the traffic, so setting up the switch like this:

Screenshot from 2016-09-06 20-48-04

(not sure why “enable VLAN functionality” being off has it working, but WTF)

and manually assigning the MAC (copied from the other router, to make switchover on Virgin Media easy) to the subinterface, and up it springs.

I’ve not yet got beyond configuring it to emulate what I was using the OEM firmware- just adding Dynamic DNS support- but quite apart from the fact it is supported, where the OEM firmware is ancient, the flexibility of hundreds of installable packages looks interesting, and according to the wiki, it will route traffic faster than OEM firmware. It certainly flatlines out the Virgin Media 100Mbit (ish) connection on a wired connection.

One Response to “OpenWRT”

  1. species5618 Says:

    I have a TP-link TL-WDR-3600 with OpenWRT, running as an access point

    it has a gigabit switch, and in a imilar way the WAN port was just a VLANd to the CPU , as i dont need that for an access point, it was easy to set it up as a 5 port access point

    my next chllange is i wantg a dedicated SSID, and may be Lan port and vlan that to a pi some outbound VPN tricks,.

    but my knowldge of VLANS is lacking
    i can trunk back to my TP link L-SG1016DE switch, but i dont want to have a trunk, i want a tagged vlan over the top of my standard network, but i as soon as i set any tagged traffic on a a OpenWrt port all the untagged traffic stops 🙁


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