Jun 222015
 

If you get hit with “RTNETLINK answers: Cannot allocate memory” when trying to add IPv6 default gateway back after losing all IPv6 -connectivity, raise net.ipv6.route.max_size.

The defaults (on my machines) were quite small compared to IPv4:

CentOS 7.0:
# sysctl net.ipv4.route.max_size
net.ipv4.route.max_size = 2147483647
# sysctl net.ipv6.route.max_size
net.ipv6.route.max_size = 4096

CentOS 7.1:
# sysctl net.ipv4.route.max_size
net.ipv4.route.max_size = 2147483647
# sysctl net.ipv6.route.max_size
net.ipv6.route.max_size = 16384

Debian 7.8/8.1:
# sysctl net.ipv4.route.max_size
net.ipv4.route.max_size = 2147483647
# sysctl net.ipv6.route.max_size
net.ipv6.route.max_size = 4096

Jun 022015
 

Finnish ISP DNA revealed their IPv6 -support for cable networks, but just listed “these devices are compatible” without more technical details.

How to get running (I used OpenWRT and EPC3825 was just a bridge):
* use DHCPv6-client
* request an /56 -prefix
* router will get an /128 -address and I found my /56 -network at the routes (with ip -6 route)
* drop a slice from it (/64) with radvd to your lan side
* remember to configure an IPv6 -firewall
* enjoy

Jan 182012
 

One way to get IPv6 /64 bridged to your LAN:


brctl addbr br0
brctl addif br0 eth0
brctl addif br0 eth1
ebtables -t broute -A BROUTING -p ! ipv6 -j DROP
ifconfig br0 up

 

Opened up: create software bridge from your WAN -interface to LAN -interface, but allow only IPv6 to fly over it. In my setup IPv4 is natted.

Dec 102011
 

Once upon a time, virtual was installed under full virtualization (KVM) -mode. Network wasn’t bridged, it was routed.

And then the problem: IPv6 -traffic flowed nicely inbound, but outbound was capped to about 128 kbps.

Troubleshooting: after googling around with ipv6, kvm and debian we came around to this, Debian bug report about GSO Ipv6 issues under KVM. It’s supposed to be fixed in 2.6.32-5-amd64 (2.6.32-39) -package…well, upgrading didn’t work for us, propably another (similar kind of) bug or something needs to be done at host-machine.

Workaround: ¬†disabling virtio_net’s gso worked for us:

ifdown eth0; modprobe -r virtio_net; modprobe virtio_net gso=0; ifup eth0