Don't assume that DHCPv6 is the same as DHCP. DHCPv6 does not provide route information because this task is handled by RA in IPv6. An IPv6 RA has flags for Managed (M), Other (O), and Autonomous (A) address configuration. None of these flags are exclusive. While most routers have the A flag set by default (which enables stateless addressing) it can be disabled, and hosts will not pick up a stateless address as a result. The M flag tells hosts to make use of DHCPv6 for an address, and the O flag tells hosts to make use of DHCPv6 for additional configuration, such as DNS. Most popular configurations: You can use the A and O flag for stateless addressing with DHCPv6 for DNS. You can use A, M, and O flags if you want every host to have a stateless address, but want to use DHCPv6 to also give some hosts a predictable address (e.g. for servers), and have them use DHCPv6 for DNS information. You can have only the M and O flags set and hosts will only use DHCPv6 for configuration. Most routers also support relaying of DHCPv6 information to a central server. For those who speak "Cisco" here is an example interface configuration for DHCPv6 only. ipv6 address 2001:DB8:100::1/64 no ipv6 unreachables ipv6 nd reachable-time 900000 ipv6 nd prefix default 900 300 no-autoconfig ipv6 nd managed-config-flag ipv6 nd other-config-flag ipv6 nd router-preference High ipv6 nd ra interval 300 ipv6 nd ra lifetime 300 no ipv6 redirects ipv6 verify unicast source reachable-via rx ipv6 dhcp relay destination 2001:DB8:200::2 ipv6 dhcp relay destination 2001:DB8:200::3 Leaving out the "no-autoconfig" will also allow stateless if your prefix-length is 64. If you don't have a 64-bit prefix stateless won't work regardless of whether the A flag is set or not. Also note, if using DHCPv6, a DUID is used instead of the MAC address, though 2 out of 3 valid DUID formats include a MAC address of the host and I haven't actually seen the 3rd implemented. DUIDs are stored after the first time they get generated, so if you're imaging hosts you'll need to included deleting the DUID as part of your imaging process, or you'll have conflicts. Ray On Thu, Jun 9, 2011 at 12:59 PM, Iljitsch van Beijnum <iljitsch@muada.com> wrote:
On 9 jun 2011, at 14:19, sthaug@nethelp.no wrote:
It is perfectly possible to use RA *only* for the default router, and not announce any prefix at all. This implies a link-local next hop.
Router advertisements always use the router's link local address, you can't get a router's global address from this. IPv6 routing protocols also pretty much only use link locals, so link local next hop and default routes are completely routine.
-- Ray Soucy Epic Communications Specialist Phone: +1 (207) 561-3526 Networkmaine, a Unit of the University of Maine System http://www.networkmaine.net/