ISP customer assignments

Wed Oct 14 01:31:36 UTC 2009

" What about anycast-type addresses (e.g. DNS servers)?  I route a few
server IPv4 /32s around in my network; do you assign a /128, a /64 (with
only one address in use), a /112, or something else?"

Yes, on any sort of multi-access segment you really should use /64s.  
A little less stringent on an all router segment perhaps, but even then I
shoot for /64s on anything that is not a PtP link ... 

/TJ

-----Original Message-----
From: Chris Adams [mailto:cmadams at hiwaay.net] 
Sent: Tuesday, October 13, 2009 9:15 PM
To: nanog at nanog.org
Subject: Re: ISP customer assignments

Once upon a time, Leo Bicknell <bicknell at ufp.org> said:
> 2) Colon's separate 16 bit chunks in IPv6.  /112's allow XXXX::1,
>    XXXX::2 to be your IP's.

Yeah, this is what I forgot about.  Makes sense now.

Another (quite possibly dumb :-) ) few questions come to mind about IPv6
assignment:

I would expect you just assign static addresses to servers.  Are there
pros/cons to using /64 or something else there?  If I'm statically
assigning IP (and DNS, etc. servers) info, why would I not just
configure the gateway there as well (especially if you just make all
local router interfaces ::1)?

What about web-hosting type servers?  Right now, I've got a group of
servers in a common IPv4 subnet (maybe a /26), with a /24 or two routed
to each server for hosted sites.  What is the IPv6 equivalent?  I can
see a /64 for the common subnet, but what to route for aliased IPs for
web hosts?  It is kind of academic right now, since our hosting control
panel software doesn't handle IPv6, but I certainly won't be putting
2^64 sites on a single server.  Use a /112 here again as well?  Use a
/64 per server because I can?

What about anycast-type addresses (e.g. DNS servers)?  I route a few
server IPv4 /32s around in my network; do you assign a /128, a /64 (with
only one address in use), a /112, or something else?