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IPv4 NAT/PAT ratios?

  • 1.  IPv4 NAT/PAT ratios?

    Posted Oct 07, 2013 01:51 PM

    If you are currently using IPv4 address translation for your client networks, will you please share with me the ratio you are currently using for real-->mapped IP addresses?

  • 2.  RE: IPv4 NAT/PAT ratios?

    Posted Oct 09, 2013 09:17 AM

    We have our ratio to be about 1 public to 80 private addresses.




    Chris Hart

    Northwestern University

  • 3.  RE: IPv4 NAT/PAT ratios?

    Posted Oct 11, 2013 10:19 AM

    thank you!


    I guess you're the only education customer doing address translation . . . ? :-/

  • 4.  RE: IPv4 NAT/PAT ratios?

    Posted Oct 11, 2013 10:34 AM


    We're not doing it now, but with our Large Public Venue (LPV) install in progress for our basketball coliseum, I anticipate having to do it as part of the implementation.



  • 5.  RE: IPv4 NAT/PAT ratios?

    Posted Oct 11, 2013 10:51 AM


    We NAT all our smartphones/Guests/Labs. We do 1 public address for every /24 private address.

  • 6.  RE: IPv4 NAT/PAT ratios?

    Posted Nov 27, 2013 09:29 PM


    While my environment is totally different (retail), I have looked at the number of sessions I typically see by devices and it seems to be in the 10-15 sessions per mobile device, with my iPhone having 20 sessions established most times due to several push accounts. 

    With a safe margin of 30 sessions per device you would likely have no issues with at least 1000 devices per IP address. At my companies retail stores we have 1 address per /21 and I have not run into any issues with running out of sessions, however my average utilization (during business) on these /21s are in the 400 device range with peaks at high traffic locations hitting 800-900 devices, again never having any issue running out of sessions. 

    If you plan at peak times to have your subnets at high utilizations at peak times I would likely do 1 per /23 or /22. I think us doing /21s pushes it, but not my call. 


    Too bad to see osuwireless needing to move to RFC1918 space. I'm a big propoent of global addressing. Maybe make best buds with some guys at MERIT and get a couple of /16s from their /8? ;) 




  • 7.  RE: IPv4 NAT/PAT ratios?

    Posted Dec 02, 2013 09:43 AM

    Thanks for your response, Matt. Good to know.


    Yeah, I hate moving to RFC1918 for our non-guests. NAT64 is what we would like to be doing, but the urgency of doing *something* exceeds the time required to implement NAT64 well. We'll do this move then get underway for building NAT64 and ideally placing these clients on IPv6 only.

  • 8.  RE: IPv4 NAT/PAT ratios?

    Posted Dec 12, 2013 11:09 PM

    We're considering going to NAT as well. IPv4 space is getting sopped up.


    Is there anyone NATing one ssid and not another? We have an open (CP) ssid and a .1x ssid with about a 20/80 split, favoring .1x. As a start I'd like to just NAT the open ssid, if that's possible.


    The NAT/PAT ratios discussed here are very helpful so far!



  • 9.  RE: IPv4 NAT/PAT ratios?

    Posted Dec 13, 2013 08:59 AM
    To close the loop, I?m targeting an average 100 sessions per client, thus a 100:1 ratio.

    This first round is to PAT our mobile devices used by student users (not staff as of yet). However, the new guest/open network I?m building will be 100% PAT. So, yes, to answer your question, others are doing a similar approach.

  • 10.  RE: IPv4 NAT/PAT ratios?

    Posted Dec 14, 2013 07:34 PM

    Ryan, I have a higher education customer in MA that is NAT'ing 1 public IP per /24.    Each controller has about 15 x /24 networks for each 802.1X network (2 at the moment).    This has been in place this semester with no apparent issues.   Check Point is NAT'ing.



  • 11.  RE: IPv4 NAT/PAT ratios?

    Posted Mar 24, 2014 04:53 PM

    We're using 50 public IP's for around a total of 25,000 internal (in use) IP's.

  • 12.  RE: IPv4 NAT/PAT ratios?

    Posted Mar 24, 2014 04:59 PM

    We do 1 public for every /22 (we do not do this on our aruba gear though...)  This seems to give us quite a bit of headroom - even during peak times...