2014-07-28 Billion 7700N ADSL Router Good News Story

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So, some time ago I bought a relatively cheap Billion 7700N ADSL Router (datasheet), which I've been running in PPPoE LLC bridging mode with a NetBSD x86-64 box keeping up the end of the PPPoE session. This has been pretty rock solid, and the router seems to do a decent job - although the 16 device WiFi limit is incredibly restrictive.

Around June, I decided to find out what IPv6 is all about, and get it up and running since my ISP (Internode) remarkably supports it. Sure, the router doesn't (or didn't) support IPv6 natively, but since I'm using LLC PPPoE bridging, that really shouldn't matter.

So, I set it up, and it didn't work. Doing some digging, I discovered that my configuration was valid, and worked with a Billion 7300A (datasheet) and a Billion 7800VDOX (datasheet) I borrowed for testing. But with my 7700N, I wasn't getting any responses to my dhcp6 solicit requests. I did notice that I was receiving ICMPv6 router advertisement packets from my ISP, but these were arriving with a PPPoE header type field set to '0', where the PPPoE RFC 2516 requires a value of '1'.

Opened a Billion support case.
Obligatory request to upgrade to latest unreleased firmware (which they provided) and perform a factory reset.
Request to set up port mirroring and grab wireshark traces. Debugging a bit further, I discover that the 7700N is flipping the PPPoE type field from '1' to '0' on all encapsulated IPv6 packets. Forwarded all this info and captures on to Billion.
Request for config dump and screen shots.
Request to enable IPv6 on the router... sigh. Explained patiently that that setting is not available for LLC PPPoE bridging, and doesn't even make sense.
Request to install something called "Teamviewer" to let them have access to my router. Dug up an old Windows laptop, and did as requested.
Engineer discovers that disabling QoS and/or setting the "Default DSCP Mark" to "No Change(-1)" rather than "default(000000)" fixes the issue!
Request to test with new firmware image, which works a treat, regardless of the QoS settings.

Ok, that took a little while, but they got there in the end, with a good result. So, consumer kit engineering level support is possible! Who'da thunk it?

Misinformation found herein copyright Paul Ripke (aka “stix”) stixpjr@gmail.com.