HEEEEEEEEEELP! Ahem. Need IP/SUBNET help.

[UrBaN]

Hellooooooooooo

I need some help with IPs/SUBNETs.

I need to provide an IP range for STATIC IPs to be assigned within - but I don't know what subnets apply to the range.

Let's make it... 169.100.100.x

Subnet?

And if I change it to 169.100.101.x? Same range I assume?

FANKS!

[Ron2K]

Do you want 169.100.100.x and 169.100.101.x to be on the same subnet, or are you talking about two different subnets here?

If one big subnet: 255.255.254.0
If two different subnets: 255.255.255.0 (and you'll need a router to connect them)

[UrBaN]

I doubt I will need more than 254 IPs, but lets be safe and say I will.

Could I safely use 169.100.100.x with 255.255.254.0, and have each IP able to directly address the others, whether on .100 or .101?

The application is this - Vodacom are assigning me Static IPs for SIM Cards to be used for VPNing and other things. I need to give them the range I want for the Static IPs.

I don't want to give them a range that won't work, or is limited. If I give them 169.100.100.x with 255.255.255.0, that allows me 254 IPs. Should be sufficient for now, if I need to change in future though, the subnet will have to change to 255.255.254.0 in order for all 508 addresses to work together, correct?

[Nuke]

169.100.100.x etc is routeable IPs in the internet, you can't use them(if you haven't brought them) They will assign you IP's in the 192.168.0.0/16, 172.16.0.0/12 and 10.0.0.0/8 ranges. The only other chance is 169.254.0.0 but that is your link local IPs (I won't use them.

What Ron said is totally true, but on point to point links(like a dial in connection on the phone/PPPoE/etc) is a bit diffrent. You don't get a subnet mask like usual, because the server gets a route directly to each IP that dials in. Your mask is a /32(a single IP) with a route to that IP.

I guess what they mean when they asked for an IP range is just what IPs to assign to you. The mask just tells them how many, you can acually ask them for 192.168.0.0/24 and 10.53.56.0/24 and it will work together fine. So you can ask for 254 IPs now and ask for more later on another range.

[UrBaN]

Nuke, These do need to be routable IPs on the internet, they are for SIM Cards which will have Static IPs so they can be connected to from wherever.

Thanks for the reply though.

[Nuke]

O ok. But if they are they will assign the IPs to you, I never heard that you can chose what IPs you like. And a full class C is going to be pretty expensive I guess, but let us know how it works.

[UrBaN]

Nuke, Well we have applied for our own APN, so instead of using the standard "internet" APN, we have our own private one, and thus Static IPs. They want to know what IP Range I want. I don't personally give a darn, but they insist they can't assign, otherwise they will be dynamic.

Frikkin noobs.

[Nuke]

Ah. But remember if you are on you own private APN you still won't be routerable from the internet. You will just be routerable inside their own network.

[UrBaN]

Nuke, Indeed, unless I be sneaky and use a PC on ADSL, using dynDNS to update an address. That way we could come in via the net, port forward onto the router and direct access to the APN and subsequent VPNs, providing credentials are known.

[Hex_Rated]

Is this for your new APN? (Edit: tooo slow)

A Subnet mask is a bit pattern - I can't remember exactly how it works but I think if you XOR the number, you get what bitmask it can connect to: eg

255.255.255.0
=
1111 1111 . 1111 1111 . 1111 1111 . 0000 0000 (separated into groups of 4 here to make it more readable for you)
XOR
0000 0000 - 0000 0000 - 0000 0000 - 1111 1111

Which means the 3 number prefix of the IP address must be the same and the last can use all 8 bits = all full 255 address range.

255.255.254.0
=
1111 1111 . 1111 1111 . 1111 1110 . 0000 0000
XOR
0000 0000 . 0000 0000 . 0000 0001 . 1111 1111

In this example we can see on the 3rd address byte the last bit is 1. Therfore you could have either 1 or 0 deviation from your host IP address.
eg:
192.168.0.1 can see 192.168.1.1

It's been a really long time since I worked with these things but that's what I remember.
PS an XOR just takes all the digits in a binary number and inverts them - 1 becomes 0 and vice verse. I like to invert it because, in my way of thinking, a bit mask of 0's means not changeable / invalid and 1's means configurable / valid... Probably from working with low level registers.

So to answer your question, yes, 255.255.254.000 will allow 512 PCs to see each other on a LAN. You can even set up PCs to use separate subnets, provided you're only using a unidirectional protocol with no handshaking (something using UDP perhaps).

[UrBaN]

Hex_Rated, Thank you for the response.

Yep, for the APN Should be up and running next week

That's the thing - we will be using UDP, TCP and other protocols, depending on the customer.

So I have told them I want 169.100.100.x using 255.255.254.0

[Hex_Rated]

Cool, so you're going with having an external internet connection connected to the entire APN? You're going to have to use some crazy port forwarding there but it will work. I wonder where that idea came from?

[UrBaN]

Hex_Rated, Well, maybe. See, one customer decides he wants statics on a private APN. Easy. Then he wants to be able to access said PRIVATE static IPs from an internet cafe in whereverville for remote support.

So I have to provide some form of access form the outside, and that's the cheapest way of doing this, other than getting a database server and breakout box from Vodacom for R3k a month...