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Thread: dhclient -6 hangs

  1. #1
    Join Date
    May 2012

    dhclient -6 hangs

    I have IPv6 autoconfiguration configured on my router which also supplies IPv6 name servers. This works fine on my Windows 7 box (I get both IPv4 & IPv6 nameservers) but I only see IPv4 server in /etc/resolv.conf on my 12.04 Ubuntu box. I get assigned IPv6 addressing just no IPv6 name servers.

    When I try:

    dhclient -6 eth0 (Or br0) it just hangs

    When I look at a network trace I see DHCP-SOLICIT and DHCP-ADVERTISE repeated over and over until I control-C

    I can see the DNS name server in the Advertise. Any ideas?


  2. #2
    Join Date
    Nov 2006
    Wisconsin, USA
    Ubuntu 13.04 Raring Ringtail

    Re: dhclient -6 hangs

    I don't know if you have resolved this already, or not. A couple of points, in case you haven't.

    (1) what does sudo rdisc6 eth0 show in the way of router advertisement flags? If the managed flag is off and the other flag is on, you are in the autoconfigured address / static DHCP case and there isn't a DHCPv6 lease (Request and Reply messages), just DHCPv6 options.

    (2) As of ubuntu 12.04, /etc/resolv.conf is being rewritten by resolveconf, which in turn is typically being fed from dnsmasq. It's now normal for /etc/resolv.conf to only contain the IPv4 loopback address (over which IPv6 AAAA queries can be made just fine). Check e.g. /var/run/nm-dns-dnsmasq.conf to get a better idea where the DNS queries are actually going.

    (3) if you are in the static DHCP case, you could probably prevent dhclient from hanging indefinitely by using the -S option for sending information-request queries instead of solicit queries.

    I'm not sure what the behavior of Ubuntu is in the presence of both DHCPv4 and DHCPv6 DNS server options. It might only plan to use the v4 ones in that case.
    Last edited by lemming465; October 16th, 2012 at 06:21 PM.

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