Geoff on IPv4 Exhaustion

Cutler James R james.cutler at
Wed Nov 16 15:33:25 CET 2011

On Nov 16, 2011, at 4:26 AM, Ted Mittelstaedt wrote, in part:

> <SNIP/>
> IPv6 isn't IPv4.  If you actually deploy IPv6 you will quickly find that
> there isn't a need for DHCPv6 to send router information.
> <SNIP/>
> Ted

Those who do not read history are condemned to repeating these arguments.

From Cutler in 2009, mildly updated:

DHCP items are end system considerations, not routing network considerations. 
The network operations staff and router configuration engineers do not generally concern themselves with end systems. 
End systems generally are managed quite independently from the routing network. And, they are more subject to the vagaries of day to day business variability. Note the "one place" in the quoted message from Owen Delong, below. 
The only overlap is broadcast forwarding for DHCP initiation. 
Besides, configuration control is hard enough for router engineers without adding the burden of changing end system requirements. Adding the forwarding entries is almost too much already! ;) 
So, to denigrate routing information via DHCP is probably due to lack of consideration of the end user system requirements. And those who denigrate DHCP and say "just use RA" make end system management that much more difficult. 
I still conclude that fully functional DHCP is a useful tool for both IPv6 systems. 

From Owen DeLong: 

OK... Here's the real requirement: 
Systems administrators who do not control routers need the ability in a dynamic host configuration mechanism to assign a number of parameters to the hosts they administer through that dynamic configuration mechanism. These parameters include, but, are not limited to: 
 1. Default Router 
 2. DNS Resolver information 
 3. Host can provide name to server so server can supply dynamic DNS update 
 4. IP Address(es) (v4, v6, possibly multiple v6 in the case of things like Shim6, etc.) 
 5. NTP servers 
 6. Boot server 
 7. Site specific attribute/value pairs (ala DHCPv4 Options) 
These assignments MUST be controlled by a server and not by the router because the router is outside of the administrative control of the Systems Administrator responsible for the hosts being configured. 

Bottom Line:  Routers and Networks don't need Router Info in DHCP, End Systems and Managers thereof do.

James R. Cutler
james.cutler at

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