20 replies to this topic

[slindborg]

I took the job of DHCP off my router as it couldnt cope.

 

I have some allocated addresses for all the stuff I know we have in the house with space for new bits etc and they sit in the 192.168.1.10-199 range and then its got DHCP for anything "new" in at 200-250 (as the router sits on 254)

iirc the subnet is 255.255.255.0

 

Can I allocate something a 192.168.2.xxx ip address and it be able to see the rest of the network devices?

[Gedi]

Why can't it cope? A DHCP server is such a low resource task that any router will have no problems coping.

 

To answer your question, no you can't do that because your current subnet will mask it off.

 

To use 192.168.2.0, change your subnet to 255.255.253.0 to open up the next block in the range, or just change it to 255.255.0.0 to give yourself 65536 addresses (192.168.0.0 - 192.168.255.255) This will make your router work a bit harder, but it can easily handle it.

[SteveA]

You can go from 192.168.1.* to 192.168.2.* but you would need some sort of device to route between the subnets as standard switching (layer 2) won't do it as Gedi has mentioned. If you have a router you will need to set up a few vlans on it and set the default gateways of the devices wanting to attach to the broadcast address on the routers vlan (e.g. 192.168.2.254). Then assign ports to vlans etc.

 

If you are going to use a class B subnet (255.255.0.0) It would be best to also use a class B private IP range (172.16.0.0) so then the default subnet mask would be correct.

Edited by SteveA, 05 January 2015 - 11:35 AM.

[slindborg]

Why can't it cope? A DHCP server is such a low resource task that any router will have no problems coping.

 

To answer your question, no you can't do that because your current subnet will mask it off.

 

To use 192.168.2.0, change your subnet to 255.255.253.0 to open up the next block in the range, or just change it to 255.255.0.0 to give yourself 65536 addresses (192.168.0.0 - 192.168.255.255) This will make your router work a bit harder, but it can easily handle it.

 

 

it was a freebie router and it didnt seem to like devices changing from being on its WLAN to the LAN (I've got a wifi extender thingy upstairs on a wired connection to the router) and as such it would lock up and need rebooting every few days. I took the DHCP task off it for something to do and the network has been flawless since.

 

So "All" I would need to do is change the subnet to 255.255.253.0 or 255.255.0.0 and that would let me use 192.168.2.xx addresses too? or do I need a layer2 switch setup aswell?

[Gedi]

Sorry, 253 was a typo, I meant 252. And yep, that will do it.

 

All a subnet is is a bitmask to tell the router which parts of an address are for routing and which parts are local. Therefore 255.255.252.0 gives 

11111111.11111111.11111100.00000000

The 1's are for routing and the 0's are local

 

Switches are dumb and can just be thought of as repeaters, so there's nothing to do there. (Your home router is most likely a router and switch in one anyway (i.e. layer 2 and layer 3))

 

Edited by Gedi, 05 January 2015 - 12:24 PM.

[slindborg]

changing the devices isnt too hard as the server is simple to access

 

is the 172 lark just "good practice" or something to improve performance?

 

I'm happy with bit masking etc, I do that loads in embedded code, but I'm not that geat with IP stuff

Edited by slindborg, 05 January 2015 - 12:23 PM.

[Gedi]

is the 172 lark just "good practice" or something to improve performance?

 

No you don't need to, the 192 range supports 65536 addresses according to the RFC http://tools.ietf.org/html/rfc1918

192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

 

Most people just use 192.168/24

You'll be using 192.168/22

Edited by Gedi, 05 January 2015 - 12:28 PM.

[SteveA]

Just good practice. On windows box if you type a class b address it will auto fill a type b mask, it can prevent typos and errors if you are configuring  a lot of devices.

[slindborg]

roger, thanks

 

I do have to manually configure about a dozen devices, but its in Arduino code  so scope for errors is high but most of it will reside in a header file.

[XXX]

Ever get the feeling that there are things that go on in the world that you have no inkling of an understanding of.......?

[SteveA]

This is fairly basic networking stuff too. It gets a lot more complicated at layer 3. HSRP, Spanning Tree, IKE, TACACS etc. I have a few shelves behind me at work full of books about this stuff. I just pretend I don't know anything like this at parties though as it makes you a bit of a social pariah

[slindborg]

I try not to admit that I work on large scale networked computer systems I generally cause layer 8 problems.

[SteveA]

Layer 8 Thankfully I don't have to deal with users.

[XXX]

Layer 8! Sheeesh....... we've all been there....!

 

yeah....

[slindborg]

Layer 8! Sheeesh....... we've all been there....!   yeah....

I don't know shizz about how networking works but there are 7 layers of guff and then layer 8 is unofficially the pink bits the fcuk everything up

[jonathansouth]

Layer 8! Sheeesh....... we've all been there....!   yeah....

I don't know shizz about how networking works but there are 7 layers of guff and then layer 8 is unofficially the pink bits the fcuk everything up

Nut loose on the keyboard. Error code: ID10T

[SteveA]

PEBKAC

 

Problem Exists Between Keyboard and Chair

[slindborg]

Changed the subnet in the dhcp server to 252 and voila, I have 192.168.0-2.xxx as a range. Dhcp pool is now in 0, allocated stuff is in 1 and the home automation lash up will sit in 2 cheers chaps

[slindborg]

Scratch that... Broke everything lmao. I think I'll just have to organise things into tighter allocated groups instead ... Reset to the start and try again

[Mangham54]

Or just by a new one pikey.