IPv6 network boundaries vs. IPv4

Is anyone out there setting up routing boundaries
differently for
IPv4 and IPv6?  I'm setting up a network where it seems to
make
sense to route IPv4, while bridging IPv6 -- but I can be
talked
out of it rather easily.

Years ago, I worked on a academic network where we had a
mix
of IPX, DECnet, Appletalk, and IP(v4).  Not all of the
routers
actually routed each protocol -- DECnet wasn't routable, and
I recall
some routers that routed IPX, while bridging IP...

This all made sense at the time -- there were IPX networks
that needed
to be split, while IP didn't need to be.  DECnet was...
DECnet -- and 
Appletalk was chatty, but useful. 

I keep hearing the mantra in my head of: "I want my
routers to route, and 
my switches to switch."  I agree wholeheartedly if
there is only one 
protocol -- but with the mix of IPv4 and IPv6, are there any
folks
doing things differently?  With a new protocol in the mix
are the
lessons of the last 10 (or so) years not as clear-cut?

> Date: Sat, 25 Aug 2007 23:56:29 -0600
> From: John Osmon <josmonrigozsaurus.com>
> Sender: owner-nanogmerit.edu
> 
> 
> Is anyone out there setting up routing boundaries
differently for
> IPv4 and IPv6?  I'm setting up a network where it seems
to make
> sense to route IPv4, while bridging IPv6 -- but I can
be talked
> out of it rather easily.
> 
> Years ago, I worked on a academic network where we had
a mix
> of IPX, DECnet, Appletalk, and IP(v4).  Not all of the
routers
> actually routed each protocol -- DECnet wasn't
routable, and I recall
> some routers that routed IPX, while bridging IP...

DECnet not routable? Not even close to true. At one time
DECnet was
technically well ahead of IP networking and far more
commonly used. It
was not until about 1993 that IP traffic passed DECnet as
the dominate
protocol and ESnet continued to route DECnet, mostly to
support the High
Energy Physics community. When the Hinsdale fire segmented
tie IP
Internet in 1988, the global DECnet Internet survived,
albeit with limits
bandwidth between the coasts.

DECnet was far from perfect and, over time, IP surpassed it
in terms of
both performance and robustness, but it was not only
routable, but
globally routed long ago.

> This all made sense at the time -- there were IPX
networks that needed
> to be split, while IP didn't need to be.  DECnet was...
DECnet -- and 
> Appletalk was chatty, but useful. 

AppleTalk was a royal pain! Gator boxes and FastPaths would
go insane
and saturate the network with broadcasts. But AppleTalk did
have some
really neat features.

> I keep hearing the mantra in my head of: "I want
my routers to route, and 
> my switches to switch."  I agree wholeheartedly if
there is only one 
> protocol -- but with the mix of IPv4 and IPv6, are
there any folks
> doing things differently?  With a new protocol in the
mix are the
> lessons of the last 10 (or so) years not as clear-cut?

Most routers are a blend of router and switch. The Cisco
6500 and 7600
boxes are probably the most popular large router in the
world, but the
heart of each is a Catalyst switch. So, the switch switches
and the
router routes, but they are both the same box.

At a major networking show we would switch the IPv6 back to
the core
routers because of bugs in the IPv6 implementations on many
systems.

You do what works best for your network. If it means
switching IPv6, so
be it. This is probably especially true when the router is
from a
company that charges substantially extra for IPv6 software
licenses. If
the is only limited IPv6 traffic, switching to a central
router might
not only be technically the best solution, but the most
reasonable
fiscal approach.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley
Lab)
E-mail: obermanes.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3
987B 3751

On 26-aug-2007, at 7:56, John Osmon wrote:

> Is anyone out there setting up routing boundaries
differently for
> IPv4 and IPv6?  I'm setting up a network where it seems
to make
> sense to route IPv4, while bridging IPv6 -- but I can
be talked
> out of it rather easily.

Why would you want to do that?

I've been tempted to do it the other way around, though. In
a hosting  
environment, you can end up with a bunch of /24s dumped on a
 
broadcast domain with a number of different customers but
the  
addresses so intermingled that you can't give each customer
their own  
VLAN. With IPv6, there is enough address space to give each
customer  
a VLAN and and address block to go along with that, which is
a lot  
cleaner.

On Sat, 25 Aug 2007 23:56:29 MDT, John Osmon said:
> 
> Is anyone out there setting up routing boundaries
differently for
> IPv4 and IPv6?  I'm setting up a network where it seems
to make
> sense to route IPv4, while bridging IPv6 -- but I can
be talked
> out of it rather easily.

We decided to map our IPv6 subnets one-to-one to our IPv4,
so each of our
routed /22 to /27 subnets gets a /64 IPv6 prefix.  This
however was just
due to the fact that our topology permitted that - your
mileage may vary.