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Confusion with DNS setup on IPv6

We finally got our IPv6 (dual-stack) circuit installed, so now the real fun begins!

We have IPv6 configured inside (on Fa0/0) and out (Serial0/3/0).  No problems here.

SLAAC works fine as any workstation I plug on the inside network (attached to Fa0/0) autoconfigs itself, just like it should.  If I change the network on the inside interface, the new network (slowly) gets propogated to the workstations--as it should.

So my question are workstations, which SLAAC themselves on the internal LAN, supposed to get DNS server information?

Do I have to manually configure DNS servers on each device?  Seems like a backwards approach -- make getting an IP easier (via SLAAC), but not I have to manually configure DNS on each device.

Can I run DHCPv6 and SLAAC RA concurrently?

I tried to enable DHCPv6 just to hand out name servers, but neither workstations pick up it, and I'm not seeing any DHCP traffic reach the workstations (via tcpdump on the linux workstation).

What does everyone else do?

For the record...I have two workstations in the IPv6 lab; 1) Windows XP, and 2) CentOS 5.5



Marcin Latosiewicz
Cisco Employee


Not sure what your current config is. And I don't want to start a holy flame war of SLAAC and DHCPv6.

One of the approaches is to push either all or some info from DHCP.

Things you should be aware of regarding DHCP/ND/DNS interaction is the O and M flags in ND.

You need to specify to hosts what parameters they should get from DHCPv6.

CA(config-if)#ipv6 nd ?


  managed-config-flag     Hosts should use DHCP for address config


  other-config-flag       Hosts should use DHCP for non-address config

Not sure if this is something you already have in your config ;-)


Thanks Marcin.  I wasn't aware of the ND flags.

I've attached the current config.  Seems like I don't have a choice but to use DHCPv6 if I want to hand out DNS servers.  But maybe I should hang out in the holy flame war forum and see...


My personal opinion on that matter is that DHCPv6 is a bit more applicable now, with solution in place and implementation almost everwhere. And as far as I remember SLAAC is only gathering traction now (in terms of vendors/OSes supporting it).

Can't quite find the data to support this, just hearsay :-)


Good enough.  Thanks.

I work for a large company (think Fortune 100) with desktops into the tens of thousands.  Not having to manage all those DHCP zones, helper addresses, etc. seemed appealing when first hearing about it.  But maybe something good can come of this yet.

Thanks again.