# IPV6 routing problem

**URL:** <https://forums.docker.com/t/ipv6-routing-problem/53821>\
**Category:** General\
**Created:** [July 10, 2018, 3:14pm UTC](https://forums.docker.com/t/ipv6-routing-problem/53821 "2018-07-10T15:14:25Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![logicethos](https://sea3.discourse-cdn.com/docker/user_avatar/forums.docker.com/logicethos/32/17684_2.png) [@logicethos](https://forums.docker.com/u/logicethos)\
**Post date:** [July 10, 2018, 3:14pm UTC](https://forums.docker.com/t/ipv6-routing-problem/53821/1 "2018-07-10T15:14:25Z")

</div>

My host has ipv6 which works fine. But my containers cant connect out on ipv6.

`Docker version 18.03.1-ce, build 9ee9f40`

/etc/network/interfaces (host)

```
iface eth0 inet6 static
address 2001:xxxx:5000:20::0010
netmask 64
gateway 2001:xxxx:5000:20::1

```

/etc/docker/daemon.json

```
{
    "ipv6": true,
    "fixed-cidr-v6": "2001:xxxx:5000:20::/64",
    "default-gateway-v6": "2001:xxxx:5000:20::1"
}

```

sysctl (host)

```
net.ipv6.conf.default.forwarding = 1
net.ipv6.conf.all.forwarding=1

```

docker run -it alpine ash -c “ip -6 addr show dev eth0; ip -6 route show; ping6 [google.com](http://google.com)”

```
259: eth0@if260: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 state UP 
    inet6 2001:xxxx:5000:20::242:ac11:2/64 scope global flags 02 
       valid_lft forever preferred_lft forever
    inet6 fe80::42:acff:fe11:2/64 scope link tentative 
       valid_lft forever preferred_lft forever

2001:xxxx:5000:20::/64 dev eth0 metric 256 
fe80::/64 dev eth0 metric 256 
default via 2001:xxxx:5000:20::1 dev eth0 metric 1024 
ff00::/8 dev eth0 metric 256 

PING google.com (2a00:1450:4009:801::200e): 56 data bytes

```

Ping just hangs

---

<div class="post-metadata">

**Author:** ![logicethos](https://sea3.discourse-cdn.com/docker/user_avatar/forums.docker.com/logicethos/32/17684_2.png) [@logicethos](https://forums.docker.com/u/logicethos)\
**Post date:** [July 11, 2018, 2:16pm UTC](https://forums.docker.com/t/ipv6-routing-problem/53821/2 "2018-07-11T14:16:12Z")

</div>

Seems this is the problem.

```
docker run -it --privileged alpine ash -c "sysctl -a | grep forward|grep ipv6;sysctl -a | grep disable_ipv6"

net.ipv6.conf.all.forwarding = 0
net.ipv6.conf.all.mc_forwarding = 0
net.ipv6.conf.default.forwarding = 0
net.ipv6.conf.default.mc_forwarding = 0
net.ipv6.conf.eth0.forwarding = 0
net.ipv6.conf.eth0.mc_forwarding = 0
net.ipv6.conf.lo.forwarding = 0
net.ipv6.conf.lo.mc_forwarding = 0

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.eth0.disable_ipv6 = 0
net.ipv6.conf.lo.disable_ipv6 = 0
```

---

<div class="post-metadata">

**Author:** ![timhughes](https://sea3.discourse-cdn.com/docker/user_avatar/forums.docker.com/timhughes/32/22154_2.png) [@timhughes](https://forums.docker.com/u/timhughes)\
**Post date:** [December 24, 2018, 9:45pm UTC](https://forums.docker.com/t/ipv6-routing-problem/53821/3 "2018-12-24T21:45:40Z")

</div>

did you manage to fix this ?

---

<div class="post-metadata">

**Author:** ![paaguti](https://avatars.discourse-cdn.com/v4/letter/p/49beb7/32.png) [@paaguti](https://forums.docker.com/u/paaguti)\
**Post date:** [March 29, 2020, 5:41am UTC](https://forums.docker.com/t/ipv6-routing-problem/53821/4 "2020-03-29T05:41:57Z")

</div>

Hey,

I’ve been struggling with this problem too. At the end, I went back to basics (i.e. BASH and the ip netns commands 😉 ) and found out that (at least in Linux) any interface you assign to a network namespace will not inherit the

> ipv6.conf.all.forwarding

or

> ipv6.conf.default.forwarding

settings.

So, unless you set the forwarding flag specifically for the container interface(s) from within the network namespace assigned to the container you want to use as a router, it will never activate IPv6 forwarding.

I have reported this as a bug in the network namespaces in the Linux kernel. Let’s see if they react.

Best,  
/Pedro A.