Been given a public IP with .128 as last octet?

[Vanadil]

Hi Guys,

I've been given a public IP address by a German company that ends in .128 . Every time that I have asked for subnet mask they just keep bizarrely refusing to elaborate and spamming me with screenshots of my IP.

What I'm not sure on is that if I'm ending in .128 the only way that this could be set up is as a point to point IP to their router which is not what I want. I need my own proper public in order to establish a VPN to the German site.

Any advice or ideas here would be great! 0.o

Thanks,

Vana

 

[bill001g]

The most likely is 255.255.255.0 but they should have told you the gateway address. You can generally guess the mask

 

[Vanadil]

You think they'd have a Class C subnet for a range of public IPs? How would that work? :S

 

[bill001g]

It depends how they are connecting to you but the vast majority of consumer connections and small business connections they make appear layer 2 to save ip.

If nothing else put the ip on a PC with 255.255.255.255 it will arp every single address. Just ping addresses around yours to see what responds. You may not get a response to the ping but you still generally see things in the arp table.

They should have given you a gateway address which should make it somewhat easier to guess the range of ip.

Bottom line you are paying for this service they should be telling you this information.

 

[Someone Somewhere]

Your IP is not the same as your subnet. An IP ending in .128 is perfectly usual; ~1/256 IPs ends in 128.

I thought that 0.0.0.0 was what you used for matching everything?

255.255.0.0 and 255.255.255.0 are the common ones.

 

[Vanadil]

An IP ending in .128 is perfectly normal for any normal class subnet. /24 for example yes I agree.

However as soon as you subnet in any form, .128 becomes a network identifier (with some exceptions, /31 and /32 for example) and when given a public IP address by an ISP it is, in my experience at least, highly unusual to get such a huge range open. You are normally allocated either a range of IPs or a single IP in a smaller range. However the company that were used to set this line up are quite proud of marketing "we can give you a unique static IP!". At the moment the only other address that I can ping on the IP range seems to be .129 , again suggesting that this is looking more and more like a /31 Subnet.

The gateway address is on a completely different IP range (my public starts with 80, gateway 217).

Gahh this damn ISP and lack of info!!!!

 

[Someone Somewhere]

If you set it to DHCP, does it pick up an address? Take a note of the settings and set them up in static.

[strike]There's no way your gateway can be in another block.[/strike] It appears it can; I'm in 203 with gateway in 111. Can't get the subnet easily, though.