implementing dhcpv6

Chuck Anderson cra at WPI.EDU
Wed Nov 4 19:31:52 UTC 2009

On Wed, Nov 04, 2009 at 05:08:30PM +0000, Simon Hobson wrote:
> I must admit that the more I find out, the less impressed I am with some 
> aspects  of IPv6 - and this is one of them. Historically I've been used 
> to setting up the routers (note plural) to do the routing, and a DHCP 
> server to configure clients.

The idea of RA is to colocate the routing configuration information 
(prefixes, gateways) with the actual routers.  You already have to 
configure this information in the router in order to correctly route, 
so why not have the router also hand this information to clients?  
There is less chance of error.

You also gain the property of fate-sharing.  So if a router goes down, 
it no longer advertises itself as an available router for the link.  
Clients will automatically choose another router on the link (perhaps 
one that had a lower preference initially).

Personally, I'd prefer it if there was a way to hand out the default 
gateway and prefix information via DHCPv6, but it just isn't there 
today.  There is an internet draft however:

Come bring your opinion to the IETF dhcwg and then beg your vendors to 
implement it :-)

> Is RA an automatic function of IPv6 routers, or is it something the  
> administrator configures ? If it's something the admin needs to  
> configure, then I see little advantage (in a DHCP environment) over  
> using DHCP to configure the client, if it's automatic then how does it 
> know what the admin actually wants ?

It is mostly automatic, although routers can usually be configured to 
send certain flags, preferences, and lifetime values.

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