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Max IP Addresses

Posted: Sun Jan 06, 2013 10:52 pm
by craiggsmith
I thought I had seen this before but I couldn't find much via a search, or on clerksupport. (Incidentally, apparently the search looks for whole words; searching on "max" didn't return posts with "maximum".)

What is the max number of IP addresses possible with each router? We have one 881W and 3 ASA5505.

I think for the 5505 it's a licensing issue, and we can have up to 50?

For the 881W I know the numbers are screwy but I assume it's somewhere around 256? I had them increase it to 150-something a couple months ago, but can't remember exactly what. My FM said the default is 52 (but I see here that it's now 108) and he just had it increased to 266, which seems like a really odd number.

Re: Max IP Addresses

Posted: Mon Jan 07, 2013 12:04 am
by jonesrk
As an STS you can see what your building has for the 881W at

Re: Max IP Addresses

Posted: Mon Jan 07, 2013 12:11 am
by russellhltn
craiggsmith wrote:he just had it increased to 266, which seems like a really odd number.
IPs are doled out in familiar chucks of a power of two. (16, 32, 64, etc). However for technical reasons, the first and last IPs are not usable. In addition, some IPs are probably assigned as static, leaving some "odd numbers" for DHCP assignment.

Re: Max IP Addresses

Posted: Mon Jan 07, 2013 8:47 am
by craiggsmith
Thanks Ryan, I knew there was a tech broadcast last month about this but never had a chance to watch it (December was kind of busy), so didn't know how to access it. I see the info now, and found out that they apparently put an 881 in another building recently! The addresses are indeed configured somewhat strangely.

Re: Max IP Addresses

Posted: Mon Jan 07, 2013 10:40 pm
by craiggsmith
Looks like I have 3 user zones:
1 quarter subnet: 64 total minus first, last, and gateway, so 61 usable with 9 static, or 52 dynamic.
2 half subnets: each with 128 total, 125 usable with 18 static, 107 dynamic.

52+107+107 = 266

Is there a reason it couldn't be configured with up to 3 full subnets? Of course that may not be desirable, but just wondering.

I wonder how they decided on the number of static addresses. I assume they aren't used by anything and are all available for us to use? The facilities equipment has their own zone. I'd like to assign static addresses to the clerk computers and maybe a few other devices. But I don't think I need 45.

The other building is configured with a single half subnet with 9 static, 116 dynamic.

Re: Max IP Addresses

Posted: Mon Jan 07, 2013 11:49 pm
by russellhltn
I'd drop a call to the networking people and see what they're willing to do. It's not like we (the STS) have any ability to do the changes ourselves.

Re: Max IP Addresses

Posted: Tue Jan 08, 2013 7:36 am
by craiggsmith
I planned to do that today, just thought I'd educate myself as much as possible first. Networking is unfortunately one of my many weaknesses.

Re: Max IP Addresses

Posted: Tue Jan 08, 2013 6:39 pm
by ryan8382
Sunday seemed to be the day that everyone noticed the DHCP range being run out. It seems like it all coincided with the official first day of the new youth curriculum. I talked with the Stake clerk who showed me that there was only 116 IP's in DHCP. I look at this I'm shocked. Our building has 3 wards that are in and out. The average person has 1 network device, and some could carry up to 3. Shouldn't this DHCP be extended? Personally i think that there should be 3 ranges 1 /24 for wired, 1 /22 or /23 for church equipment and lastly a /21 for public.

I work for a school district as a network administrator. We put in a public wifi last year and have had some learning in the area. We changed the lease time from 24 hours and lowered it to now 1 hour. Currently the public wifi uses a /22 and we are looking to make it larger to accommodate more devices. I don't know the Cisco ISR 881W, i'm more used to enterprise equipment.

Re: Max IP Addresses

Posted: Wed Jan 09, 2013 2:09 am
by john84601
Wireless is by definition 'shared bandwidth'. Even enterprise grade WAPs get overloaded between 20-30 users.

If you increase the size of the DHCP scope, yes you may be able to avoid the issue of people not being able to pull a DHCP address. Although shortening the lease to between 1-2 hours will help this a lot as well.

But there seams to be this notion that increasing the scope will fix all of your wireless issues. If you have a building with (1) 881w and (3) 1041n (this seems to be a common config) and more than 100 devices connected to the network... you're going to have mediocre performance at best (combine this with a DSL internet connection!). If one or more of those 100 users starts to stream media.... then your really hosed.

For those of you who say you have 75-100+ devices on a network at one time (very possible in a building with 2 wards that overlap)... your going to have to educate your members. Disconnect from LDSAccess if you're not actively using it.

Re: Max IP Addresses

Posted: Wed Jan 09, 2013 8:01 am
by craiggsmith
Good points everyone for sharing your expertise. I've noticed in stores such as Home Depot and Walmart that their free wireless is useless for these same reasons, and I no longer try to use it. I think the assumption here though is that most people are simply connecting with their mobile devices automatically and not doing much, mainly email.

In the building with 266 connections we have a 20 Mbps cable connection. The other building with 116 addresses has a 6 Mbps DSL connection. I don't know if the problems Sunday were due to lack of addresses for the widespread wireless failure that has been reported, as no one told me about the problem until Sunday night. And of course they haven't given us visibility into that aspect of the firewall yet.

Frankly it seems the new equipment has done more harm than good; I've lost all control and visibility of the network. I'm about ready to go back to our own equipment (except facilities took some of it).

I think the solution is to be able to control who gets on, and I was quite disappointed that they scrapped the lds account project. At this point I think the only solution is to change the wireless key and only give it to leaders and teachers, tell them not to give it out, and change it on a regular basis. But we can't do that either.