[GRLUG] IPv6 network nightmare

Adam Tauno Williams awilliam at whitemice.org
Mon Sep 8 12:07:46 EDT 2014

On Mon, 2014-09-08 at 10:41 -0400, Mark Farver wrote:
> On Sep 8, 2014 10:17 AM, "Adam Tauno Williams"
> <awilliam at whitemice.org> wrote:
> His argument that ARP is well supported in hardware but multicast
> isn't is probably fair.  Networking hardware has lagged in this area
> for years.
> The network community has had an inappropriate dislike of multicast
> since it was first specified and many network admins and vendors avoid
> it to this day. 

Yep.  To be fair multicast wasn't even a glimmer in the designers eye
when IPv4 was brought forth into the world; it was tacked on, and many
of the tools make it feel that way. This is an area IPv6 cleans up
considerably.  And since an IPv6 stack implementation has ground-up
inclusion we will hopefully see much more consistently and universality
of support.

> Campus scale IPV6 installs are fairly common in academia and I've
> never heard of one going sideways like this 


> And while it is convenient and sometimes unavoidable, extending all of
> your L2 domains to the core is asking for trouble even without IPV6. 


> (Nothing more fun than watching a network loop take down the entire
> core switch.).  The risk of network loops goes down substantially if
> you don't have a complicated spanning tree and if your north south
> links are L3.  Don't think of spanning tree as a magnificent oak.  It
> is more like Kudzu...

Preach it brother!  Use spanning-tree and the like when really
necessary, otherwise route [call it Layer 3 Switching if your boss likes
those buzzwords more].

> He doesn't go into details on the hardware but from his description i
> think they are using a layer 2 switch with rudimentary L3 abilities
> (probably a Ex8200)... This is acceptable for small networks but not a
> campus size one no matter what the sales guy says.  Alas core routing
> hardware (juniper MX series is my fav) is fantastically expensive.

But very good routing performance, suitable for most sites, can be had
with pretty reasonably priced hardware.

Adam Tauno Williams <mailto:awilliam at whitemice.org> GPG D95ED383
Systems Administrator, Python Developer, LPI / NCLA

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