Pure IPv6 based networking

This is as yet, a draft.

IPv6 has been ‘the future’ for over a decade now. Making it work right, in time for the ‘World IPv6 launch’, June 6, 2012, is one of the many goals of cerowrt.

This is how to setup a pure ipv6 based network behind the router itself. While useful as an academic exercise, it is also useful in exposing what, exactly, needs to be done in order to have a working ipv6 based network.

Get IPv6 working

There are multiple ways to get ipv6 working. The best, of course, is native ipv6, which is coming available from multiple providers, notably comcast. You can also tunnel (6in4), or use 6to4. As cerowrt has 6 default interfaces it is best to get at least a /60, preferably a /56 or better, ipv6 network to play with.

Present versions of cerowrt try really hard to come up automatically in 6to4 mode. This functionality will be disabled by default
in the near future.

For purposes of this discussion I’m merely going to document how bloatlab 1 is configured. The bloatlab has a /60 ipv6 delegation from isc.org, thus leading to the possibility of 16 distinct ipv6 networks. There is also a ‘main’ network on which an array of routers and test equipment are configured.

The internal address range we’re using is: 2001:4f8:3:aa00::/60. Any time you see addresses in this range in this document, please substitute your own.

Configure cerowrt on the right ipv6 addresses

This is in the case of a native ipv6 enabled network. For 6to4 or 6in4 instructions, there will be some more notes soon.

config interface 'ge00'
        option ifname 'ge00'
        option proto 'dhcp'
        option accept_ra '1'
        option send_rs '1'

config interface 'se00'
        option ifname 'se00'
        option proto 'static'
        option ipaddr ''
        option netmask ''
        option ip6addr '2001:4f8:3:aa0c::1/64'

The first stanza for ‘ge00’ accepts whatever ipv6 address is assigned by the ‘RA’ protocol and may not be what you need - dhcp-pd is being worked on at present. I note that your should be setting ‘ipaddr’ to whatever you want to have for your network, not the above.

Add the ip6addr option to each additional interface, incrementing the 4th field appropriately. Note that the /64 is not actually required… In the case of the two meshed interfaces (gw01, gw11), the correct approach is to use the same, single /128 for both (e.g. 2001:4f8:3:aa0e::1128).

It’s simplest just to reboot at this point. Radvd will automatically pick up the ipv6 addresses, and hopefully the default gw will be supplied by the upstream ipv6 router….

Check to see if you have ipv6 addresses on clients after the reboot

And, do you have a default gw?

If so, awesome. Things like ping6 huchra.bufferbloat.net should ‘just work’. If they don’t, a horde of other problems could be happening and are currently beyond the scope of this document.

Cope with security issues

Get DNS to work right

The integral bind9 server in cerowrt is fully capable of doing DNS over ipv6. However it makes a difference between ‘internal’ and ‘external’ views of its database that need to be managed via access control lists (acl)s. Edit /etc/chroot/named/etc/bind/conf/acls.local.conf to have a line in it that matches the address ranges you are using

acl mylan {
// 2002:XXXX:YYYY::/48; if you are using a 6to4 address

IF you have a local forwarder that is ipv6 and dnssec enabled, you can edit the forwarders.conf file in this directory to suit, and uncomment the forwarder line in named.conf.

then restart bind

killall bind; 
nslookup ::1
nslookup ipv6.google.com

You can go much further with this than this, notably doing reverse dns, etc, but not today. It is certainly my hope to get to where ipv6 is as transparent to use as ipv4 at some point. I note that most of google’s services when bind9 is operating over ipv6, automatically come up on ipv6, so there is generally no need to use ‘ipv6.google.com’ when things are working properly.

Enable the polipo web proxy

Web proxies have been a standard component of the http protocol since the early days, and despite falling into disuse of late, are the simplest way to retain universal to-the-web access, by using the proxy to translate between ipv6 internally to ipv4 or ipv6 based websites externally. However polipo needs to be reconfigured slightly to accept connections within your network over ipv6. Add the following two lines (Again, substituting your own ipv6 address range) to /etc/config/polipo

        option 'dnsNameServer' '::1'
        list 'allowedClients' '2001:4f8:3:aa00::/60'

It is also useful to use polipo as a caching web proxy, by putting a flash drive into the cerowrt box and enabling the cache option, but for now

/etc/init.d/polipo restart

Enable the web proxy on the clients

there are a few ways to do this, the most straightforward is merely to put the ipv6 address of the polipo proxy in your ‘network connections->proxies’ entry for your web browser. A more ‘right’ way might be to use the ‘wpad’ auto proxy configuration facility,
which would be able to supply the right configuration information automatically…

At this point you should be able to surf the web with only minor breakage. In my own tests the only thing that broke was the macromedia protocol used in some TED talks. That is not to say this is perfect….

Enable ipv6 nameservice lookup on clients

Easiest way is to just stick the appropriate

nameserver 2001:4f8:3:aa0c::1

in /etc/resolv.conf. In an ideal world, a service such as rdnssd or dibbler-client, will do this bit of grunt work for you.

I use git and have to proxy it through polipo

While a few git services already have ipv6 support, github (my main one) does not, so I do this:



Samba ‘just works’ on ipv6. However there are some firewall rules that will affect getting from the ‘guest’ networks to the ‘secure’ networks contained in /etc/firewall.user that should probably be examined.

Try to use ipv6 enabled services.

For example, ipv6.google.com, and irc chat services such as freenode, are already on ipv6. My primary email servers are also on ipv6, as well as my jabber server. Admittedly, that’s me. It is not terribly hard to get this stuff running on various servers, but I’ll leave that for another document.

Turn off ipv4 entirely

So you have all the above working and want to go beyond the bleeding edge?

Turn off ipv4 entirely on a client and see what happens. On Linux, it’s straightforward:

ip -4 addr show dev whatever
# take that address
ip -4 addr del dev whatever that_address

And at least until your dhcp refreshes, you will be purely ipv6 and can experience all the pleasures (if any exist) and pain (plenty) that ipv6 can bring to your network.

Known Problems


Having a dns search list was a late addition to the RA protocol and is still not widely adopted. This (as one example), makes implementing wpad support difficult. A test patch is in progress on the router itself, but as for clients…

Security with polipo

The polipo web proxy is a single tier proxy, in that it has no means of discriminating between ‘allowed’ and ‘restricted’ networks. By making it available across the entire allocated ipv6 range as done above, the concept of local secure internal and guest networks has been bypassed, anyone that can connect to the proxy can access various web-like services on both ‘guest and secure’. This is probably not what you want, but at least the above restriction keeps people from outside your lans, out. Without finer grained access controls in polipo such as what squid has, I don’t know how to fix this….

Security with ip6tables

The ip6tables rules have not been fully evaluated as to their effectiveness and thoroughness.

To edit this page, submit a pull request to the Github repository.
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