Archive for December, 2013

Turning Comcast IPv6 Up on a NetGear 3800 with OpenWRT

December 11, 2013 at 13:14 · Filed under IPv6, Routers & Routing

The first problem was a pre-release kernel. I used LuCI, the web interface, to flash openwrt-ar71xx-generic-wndr3800-squashfs-sysupgrade.bin, and needed to be patient with 15 minutes of twirly. The flash lost my ssl package, so I also had to

opkg install uhttpd-mod-tls

Thanks for Chris Adams for all clue, and John Brzozowski for diagnostics and support, I loaded the necessary packages

opkg install ip6tables radvd wide-dhcpv6-client ip

Then I hacked /etc/config/dhcp6c

config 'dhcp6c' 'basic'
        option 'enabled' '1'                            # 1 = enabled; 0 = disabled
        option 'interface' 'wan'                        # This is the interface the DHCPv6 client will run on
        option 'dns' 'dnsmasq'                          # Which DNS server you run (only dnsmasq currently supported)
        option 'debug' '0'                              # 1 = enable debugging; 0 = disable debugging

        # Send options (1 = send; 0 = do not send)
        option 'pd' '1'                                 # Prefix Delegation
        option 'na' '1'                                 # Non-Temporary Address
        option 'rapid_commit' '1'                       # Rapid Commit

        # Request options (1 = request; 0 = do not request)
        option 'domain_name_servers' '1'
        option 'domain_name' '0'
        option 'ntp_servers' '0'
        option 'sip_server_address' '0'
        option 'sip_server_domain_name' '0'
        option 'nis_server_address' '0'
        option 'nis_domain_name' '0'
        option 'nisp_server_address' '0'
        option 'nisp_domain_name' '0'
        option 'bcmcs_server_address' '0'
        option 'bcmcs_server_domain_name' '0'

        # Override the used DUID, by default it is derived from the interface MAC
        # The given value must be uppercase and globally unique!
        #option 'duid' '00:03:00:06:D8:5D:4C:A5:03:F2'

        # Script to run when a reply is received
        option 'script' '/usr/bin/dhcp6c-state'

# Define one or more interfaces on which prefixes should be assigned
config 'interface' 'loopback'
        option 'enabled' '0'                            # 1 = enabled; 0 = disabled
        option 'sla_id' '1'                             # Site level aggregator identifier specified in decimal (subnet)
        option 'sla_len' '0'                            # Site level aggregator length (64 - size of prefix being delegated)
                                                        # e.g. /60 from ISP -> 64 - 60 = 4
config 'interface' 'lan'
        option 'enabled' '1'
        option 'sla_id' '1'
        option 'sla_len' '0'

Then /etc/init.d/dhcp6c start and see what you get. You should have an RA-assigned IP on your wan interface and a PD-assigned /64 on the LAN. If you configure radvd (just set it with no prefix listed), dhcp6c will automatically re-configure it to give out addresses from the /64.

Now get Router Advertisement working, hack /etc/config/radvd to

config interface
        option interface        lan
        option AdvSendAdvert    1
        option AdvManagedFlag   0
        option AdvOtherConfigFlag 0
        option ignore           0

config prefix
        option interface        lan
        # If not specified, a non-link-local prefix of the interface is used
        list prefix             ''
        option AdvOnLink        1
        option AdvAutonomous    1
        option AdvRouterAddr    0
        option ignore           0

config rdnss
        option interface        lan
        # If not specified, the link-local address of the interface is used
        list addr               ''
        option ignore           0

config dnssl
        option interface        lan
        list suffix             rg.net
        option ignore           0

Then
/etc/init.d/radvd start
/etc/init.d/dhcp6c start

At this point, we had the /128 on our WAN interface, and the /64 on the LAN interface. But, from the OpenWRT, we could not ping an external IPv6 address. Hours were spent chasing various ghosts, when we found the fix,

sysctl -w net.ipv6.conf.eth1.accept_ra=2

From a hint in New Zealand, accept_ra=1 means “only accept RAs if forwarding is disabled”. Turns out to be documented in the 3.12.4 kernel source clue pages. Once you have forwarding enabled, you have to have accept_ra=2 to override that.

:~# ping6 psg.com
PING psg.com (2001:418:1::62): 56 data bytes
64 bytes from 2001:418:1::62: seq=2 ttl=52 time=70.286 ms
64 bytes from 2001:418:1::62: seq=3 ttl=52 time=70.090 ms
64 bytes from 2001:418:1::62: seq=4 ttl=52 time=71.169 ms
64 bytes from 2001:418:1::62: seq=5 ttl=52 time=77.020 ms

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An Automated System for Emulated Network Experimentation

December 11, 2013 at 13:01 · Filed under Conferences, Routers & Routing

Simon Knight presented our paper, An Automated System for Emulated Network Experimentation, at CoNEXT 2013 in Santa Barbara.

Emulated networks and systems, where router and server software are run in virtual environments, allow network op- erators and researchers to perform experiments at large scale more economically than in testbeds. Running real code pro- vides a greater level of realism than simulation.

However, large scale comes with a problem: running real software means each test needs at least as much configura- tion as a real network. To recognise the true value of emula- tion at scale, we need to reduce the complexity of building, configuring, deploying, and measuring emulated networks.

We present a system to facilitate emulation by provid- ing translation from a high-level network design into a con- crete set of configurations that are automatically deployed into one of several emulation platforms. Our system can be used to construct multi-domain networks in minutes, and is scalable to networks with over a thousand devices. It is modular, allowing support for different protocols, topology designs, and target platforms: Quagga, JunOS, IOS, etc. Users, from both the research community and industry, have already demonstrated its value in research and education.

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