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Ethernet Switches & Routers

Occasional Contributor
Posts: 18
Registered: ‎02-04-2013

IPv6 Router Announcements and DNS

[ Edited ]

Hi All --


We have a SX1600 switch/router running 7.4b firmware and we're deploying IPv6. I'm using Router Announcements to advertise global unicast prefixes and to enable DHCPv6 on the subnets where its needed. Here's the problem: on the non-DHCPv6 subnets where stateless autoconfig+RA is used to set the host addresses I have no way of auto-assigning DNS server addresses. RFC says this can be done by including the addresses in the Router Announcements but it's not mentioned in the documentation (or I can't find it -- the Router Announcement settings are scattered throughout the manual). Am I stuck with manually configuring DNS server addresses or is there a way to use RAs to do this that I haven't found?


Thanks in advance!




I've been doing some more reading and I think I canask this a littler more clearly now:


There are 4 flags of interest in a router announcement:


On-link                                           if 1 the included prefix is added to the prefix list

Autonomous                                  if 1 the prefix and the 64-bit interface ID are used to derive an address 

Managed Address Configuration   if 1 a stateful address configuration protocol is used to obtain additional addresses

Other Stateful Configuration          if 1 a stateful address configuration protocol is used to obtain additional configuration parameters


By "stateful address configuration protocol" I'm assuming DHCPv6


So the first 2 flags control whether the host uses the RA prefix and theEUI-64 MAC-based interface ID as an address or not

and the 2nd 2 flags control whether or not a host uses DHCPv6 to get its address and whether or not it gets other things like DNS server addresses, etc. from DHCPv6.


In the best of all worlds I would be able to set all 4 flags to one value or another and include both a unicast prefix and also DNS server addresses in the router announcement, thereby having full control over my autoconfiguration environment.


So here we go again (clearer,I hope!) In an SX1600 running 7.4b firmware with IPv6 enabled on the switch and on a VE router interface, what flags can I set, and how many prefixes can I add to the IPv6 router announcements coming from the VE?


Thanks again!


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