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IPv6 and networking pain

I’m honestly reconsidering my scepticism towards curses.. mostly because the past two months don’t make much sense without taking that into consideration. I’ve had a long list of hardware, network and power issues, and jobs ended up being bottled up due to that.

Not the latest, and not the worse (but there on the upper side of the list) of said issue happened with the DAP-1160 bridges/access points I used to connect the network segment in my office to the router downstairs. The problem there is that for a long series of reasons I can’t reach it with either an ethernet cable or a powerline adapter, and so I decided to use gigabit within the office, and jump with wireless to the router.

I’ve got those two bridges for about two years now, and they worked mostly well. Mostly, not perfectly. In the past month, though, they started acting up, requiring too often a reboot… the problem is likely tied with them running continuously for a few months and then being turned on and off repeatedly due to the power company blacking me out (14 hours in 14 days.. two lumps of 5 hours, plus a number of on-and-off spikes).

My original implementation for getting this setup to work involved an OpenWRT powered router, and subnetting the office.. but the subnetting became easily a bother, as it added one more router for me to manage, and I didn’t intend to proceed that way. I then replaced said router with Enterprise/Yamato with a WLAN card, but that had its share of troubles as well. At the end I went with the two D-Link devices that created a seamless Ethernet bridge between the two segments, yai!

And now they started failing, so I had to replace them. And since I was out to replace them I wanted to use 11n hardware to run on the 5GHz band rather than 2.4, to avoid most of the interference otherwise present. So after a bit of googling around I ended up buying two Cisco Linksys devices, a WAP610N access point and a WET610N bridge. They are designed to work together, and thus they should have been perfect. Should being the keyword.

What happens with these? Well, the throughput is nice indeed, it’s much faster to connect to the router now. But at the same time.. I lost all IPv6 capabilities.

Now, I learnt the hard way at the time that the 802.11 specifications do not include provisions for wireless-to-Ethernet transparent bridges, and all implementations of those are custom implementations of the manufacturers. I thought Linksys solved that in such a level as well.. but it turns out it didn’t. It actually did something a tad smarter, for the kind of usage they foresaw their hardware to be used for. They parse the third level packages, in particular it seems they parse the ARP packets, to tell the access point which address to send their way… a sort of Network Address Translation at the second level.

Unfortunately, they do not do the same for what concern the IPv6 NDP, so IPv6 is simply broken here. To be honest, IPv6 works fine in the network segment, becaues the router advertisement is sent in broadcast, and thus received probably, but all the unicast IPv6 traffic from the router to the bridge (not the other way around, btw) is dropped.

I’m not sure if I should just live with it or if I should find a more proper replacement for the 1160 devices. If somebody know hardware capable of doing such a transparent bridge between wireless and ethernet on the 5GHz band, it would definitely be welcome.. in that case, the Linksys bridge will just limit itself to my bedroom (where it would connect just the consoles and TV, none of which is IPv6 compatible anyway), and the access point would replace the current 11g public network I use for the devices outside of my office.

In the mean time I have more issues to solve. Sigh.

Comments 4
  1. Simply use hostapd (wds_sta) with two Atheros cards. It will use all four address fields of the frame (though apparently not unspecified).

  2. I tried hostapd with an ath5k card, and the result has been … bad. Most definitely I don’t want to try running two instances of that, mostly because I don’t really want to hand-maintain more than one router in the house.. I wish I could really avoid the access points as well, but that’s much more unlikely as it is.

  3. WDS would work, but the problem with WDS is that it’s so fragile that it breaks more often than it works. I tried it before and simply failed to get it to work… I’m not sure I want to try that again anytime soon.As for the WET mode, the ARP-NAT implementation they note being used by Broadcom’s drivers doesn’t seem much different from what I described here and in the post afterwards, and I thus doubt it works with IPv6 (given that it doesn’t use ARP).It’s probably not a coincidence that the Linksys bridge device is *WET* 610N.

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