Mark Andrews wrote:
I would have thought that router renumbering should be no
harder that host renumbering. Essentially all you are
changing is the higher (/48 normally) prefix bits. All
that is required is a method to distribute the set of
prefixes in use with a set of tags (global, deprecated,
ula, advertise in RA, etc.).
I think there has been hype on both sides of this question. Router
renumbering used to be VERY annoying. I've now published several times
on the subject and I can say that it's not as hard as it was, but it's
not as easy as it could be. Specifically, prefix delegation should do
the job for small routers, particularly in the consumer market. Making
use of PD in the enterprise is more experimental, I would say, because,
as Bill alludes, there are quite a number of knobs to play with.
Consider that a typical enterprise router not only has interface
addresses and routing subsystems and firewalls, but may also have such
fun as VRRP/HSRP configurations, load balancing capabilities,
NetFlow/sflow collectors, multicast configuration that has some unicast
addresses hidden in it, management configuration (e.g., SNMP, SYSLOG,
other), and the like.
In my opinion, this means that the router of the future needs to look a
little different, and this has implications for other subsystems. Much
of this could conceivably be hidden with DNS, but the router itself
needs to function not just deterministically but predictably down to the
minute in terms of which addresses it is using. DNS isn't very good at
that because your TTLs are based on when you query, and are tied to
relatively fixed configurations, but it can be used for many things even
so. And today you can do that in many portions of the configuration -
but not all.
It is possible to abstract out much of the configuration EVEN WITHOUT
DNS, and modularize those things that will change. And we've done
*some* of that at Cisco, but we all could do more.
Eliot
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