Multiple addresses [was Node Requirements: Elevating DHCPv6 from MAY to SHOULD]

[Brian E Carpenter <[e-mail]>]

Ray,

On 2011-05-31 08:05, Ray Hunter wrote:
...
> Which source address (SLAAC/DHCPv6) would be used by the client for an
> outbound session if a SLAAC address and a DHCPv6 were both configured on
> the same link and with the same prefix, in the absence of a flag? 

Whichever RFC3484bis or the local policy table determines;
this is orthogonal to the question of where the addresses come from.

> Think
> dynamic DNS too: which (destination) address(es) would be auto
> registered at the server end?

Both, if it's a server and you've chosen to use dynamic address
allocation for servers. Again, this is orthogonal to where
the addresses come from. It's going to be SOP for servers with
multiple addresses.

> The main argument I'd make for network managers being able to
> predictably choose for centrally administered static addresses via
> DHCPv6 if they want to, is to be able to preserve existing
> semi-backward-compatible behavior similar to IPv4 + DHCPv4 + DHCP relay
> (which I realize is far from perfect). There are a lot of operational
> people who currently rely on having predictable IP addresses for
> accounting, audit, scripting, firewall rules, neighbor filtering, fault
> tracing, reverse DNS, policy based routing, setting DSCP in QoS, any
> other number of ACL's  .... (completely putting to one side any argument
> whether that is good or bad practice, or whether there are now better
> solutions to achieve these effects)

Yes, there are lots of bad habits that have grown up over the years
that IPv6 challenges. For example, setting the DSCP *as a function of
the source address* makes me cringe. We're going to have to get used to
the fact that IP addresses are not constants.

    Brian