New IP Address subnets and safe static IP Address for new UK meetinghouse internet

Discussions about Internet service providers (ISPs), the Meetinghouse Firewall, wired and wireless networking, usage, management, and support of Meetinghouse Internet
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carljokl
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New IP Address subnets and safe static IP Address for new UK meetinghouse internet

Postby carljokl » Mon Mar 05, 2012 2:40 am

I have been trying to help out a missionary assigned as an employment specialist to share a printer between two computers provided for employment services within one building.

At the moment, only one computer has been able to connect to the printer via USB. The printer has its own built in print server. I have tried to set the printer up on a fixed IP Address. One thing that I noted though was that the meetinghouse subnet appears to be 255.255.255.192 i.e. it is only a 64 address subnet. The DHCP addresses seemed to be allocated in the 10.x.x.100+ range. I am already used to the meeting houses using 10.x.x.x range with just the last number being used for the address, however I am used to the full 255 addresses being available per meeting house. The wireless access points would run on an address of 10.x.x.1 or 10.x.x.2 ascending up to the number of access points used. The end of the static block range was 10.x.x.9 and things like servers or printer servers could use these addresses starting from there and working backwards. With the subnet being only 64 addresses long I am not sure what provision has been made for a Static IP Address range within that block. Does anyone know?
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aebrown
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Postby aebrown » Mon Mar 05, 2012 5:47 am

carljokl wrote:I have tried to set the printer up on a fixed IP Address. One thing that I noted though was that the meetinghouse subnet appears to be 255.255.255.192 i.e. it is only a 64 address subnet. The DHCP addresses seemed to be allocated in the 10.x.x.100+ range.


When you are working with a /26 subnet, there are typically 4 possible gateways: 10.x.x.1, 10.x.x.65, 10.x.x.129, or 10.x.x.193. You didn't mention what the default gateway is for that meetinghouse network. With a 255.255.255.192 subnet mask, I really doubt that the DHCP addresses start at 100, but since you said "100+" I would guess that the default gateway is 10.x.x.129, and the DHCP addresses start at something like 10.x.x.138.

carljokl wrote:I am already used to the meeting houses using 10.x.x.x range with just the last number being used for the address, however I am used to the full 255 addresses being available per meeting house.


If you are used to a "full 255 addresses being available", then you must typically use a 255.255.255.0 subnet mask, which is used for a /24 subnet. But there's nothing magic about that kind of subnet; it's just an arbitrary (but common) choice for consumer grade firewalls. The PIX 501 and ASA 5505 meetinghouse firewalls often used a smaller subnet with only 64 addresses within the subnet.

carljokl wrote:The wireless access points would run on an address of 10.x.x.1 or 10.x.x.2 ascending up to the number of access points used.


When you are using a 255.255.255.0 subnet mask, typically the gateway is at the .1 address, and then fixed IPs start at .2; I've never seen a WAP at the .1 address.

carljokl wrote:The end of the static block range was 10.x.x.9 and things like servers or printer servers could use these addresses starting from there and working backwards. With the subnet being only 64 addresses long I am not sure what provision has been made for a Static IP Address range within that block. Does anyone know?


The exact size of the static block is something you'd have to ask the Global Service Center. But the size you mentioned is not uncommon. In a /26 (64 address) subnet, the base IP address can be .0, .64, .128, or .192. In that scheme, the gateway is at 1 relative to the base IP; WAPs are typically at 2, 3, 4, etc.; and other static IP addresses are from there up to 9. So if your gateway is at 10.x.x.129, then your base IP is .128; your WAPs are at .130, .131, .132, etc.; and static IPs would be from there up to .137. DHCP addresses would then start at .138 and could go up to 10.x.x.191 (depending on the size of the license -- again something the GSC can tell you).
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carljokl
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Postby carljokl » Tue Mar 06, 2012 12:47 pm

It was actually a 10.x.x.65 based subnet. I wasn't actually at the computers when I asked the question but though to ask later. It is not really a matter of understanding subnets and how they work, it is about knowing where the Church puts the static address block for these subnets. It might be an educated guess to assume that the first couple of addresses after the router. It is an educated guess and hopefully we shall find out if it breaks anything.
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jdlessley
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Postby jdlessley » Tue Mar 06, 2012 1:16 pm

carljokl wrote:...it is about knowing where the Church puts the static address block for these subnets. It might be an educated guess to assume that the first couple of addresses after the router.
For the Cisco 881W that information is in the fourth paragraph here.
JD Lessley
Have you tried finding your answer on the LDS.org Help Center page or the LDSTech wiki?


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