Forum - The return of 2000::/3 ? :: SixXS - IPv6 Deployment & Tunnel Broker

The return of 2000::/3 ?

Shadow Hawkins on Monday, 27 October 2003 22:36:08

I discovered this a few minutes ago. I'm using linux with vanilla kernel 2.4.22 and had problems setting up a router to my subnet. So I did the following: 1. Set up an IPv6 addres for my LAN interface on the router

ip -6 addr add 2001:960:647:1::1/64 dev eth0

2. fired up radvd for 2001:0960:0647:1::/64 On the client the interface autoconfigured so it should work from now on but... ...I tried to ping noc.sixxs.net but got "No route to host" so I ended up checking my route tables over and over, swithing IP's turning of radvd etc. The last resort was setting up a 2000::/3 route to my POP on the router... and it worked! I checked it several times and it seems that w/o the 2000::/3 it doesn't work! This is strange because the router had a working tunnel for about 2 weeks now and was doing fine without it. Any thoughts? Or did I lose something from the kernel ChangeLog ? ;)

The return of 2000::/3 ?

Jeroen Massar SixXS Staff

on Monday, 27 October 2003 22:51:27

Dump your "ip -6 ro sho" table, that might show why it doesn't work.

The return of 2000::/3 ?

Shadow Hawkins on Tuesday, 28 October 2003 15:09:18

Here it is:

2001:960:2:8b::/64 via :: dev sixxs proto kernel metric 256 mtu 1280 advmss 1220 2001:960:647::/48 dev eth0 proto kernel metric 256 mtu 1500 advmss 1220 2000::/3 via 2001:960:2:8b::1 dev sixxs metric 1024 mtu 1280 advmss 1220 fe80::/64 dev eth0 proto kernel metric 256 mtu 1500 advmss 1220 fe80::/64 dev eth1 proto kernel metric 256 mtu 1500 advmss 1220 fe80::/64 via :: dev sixxs proto kernel metric 256 mtu 1280 advmss 1220 ff00::/8 dev eth0 proto kernel metric 256 mtu 1500 advmss 1220 ff00::/8 dev eth1 proto kernel metric 256 mtu 1500 advmss 1220 ff00::/8 dev sixxs proto kernel metric 256 mtu 1280 advmss 1220 default via 2001:960:2:8b::1 dev sixxs metric 1024 mtu 1280 advmss 1220 unreachable default dev lo proto none metric -1 error -101 advmss

Without the 2000::/3 route, clients using this box as a gateway will get "No route" whereas the router will operate normally.

The return of 2000::/3 ?

Shadow Hawkins on Tuesday, 28 October 2003 05:58:43

It's a known issue in Linux 2.4 with broken IPv6 support that a router does not honour its own "default" route for routed packets, so you must explicitly target them (and 2000::/3 is almost equivalent to a default route). I think the other stack fixed it but has other problems - I've never used IPv6 on something else than MirBSD/OpenBSD/NetBSD and win2k/2003 yet.

The return of 2000::/3 ?

Shadow Hawkins on Tuesday, 28 October 2003 15:08:57

That's strange because they repaired that in 2.4.21 or 2.4.20 and now it's broken again.

The return of 2000::/3 ?

Jeroen Massar SixXS Staff

on Tuesday, 28 October 2003 16:51:43

2.4.21 and up or USAGI should allow default route even when IPv6 forwarding is enabled. jeroen@purgatory:~$ uname -a Linux purgatory 2.4.21 #1 Sat May 3 03:22:00 CEST 2003 i586 GNU/Linux jeroen@purgatory:~$ ip -6 ro | grep default default dev sixxs metric 1024 mtu 1280 advmss 1220 I am quite sure of it :) But they *could* have borked it in 2.4.22 ofcourse

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