Networking #101

Hi all,

Can you guys and girls confirm this is correct?

I've been give this info:

A block of 5 static addresses:
xx.xx.xx.49 thru to xx.xx.xx.53
Subnet: 255.255.255.248

Network Address: xx.xx.xx.48
Router/Hub address: xx.xx.xx.54

Now - I'm assuming if thats correct that the routers WAN IP should be static on xx.xx.xx.54 - what address do I give a firewall? Should I use the xx.xx.xx.49 address or can I use any from the static block?

What device would I assign to the network address, or what's it purpose?

I kind of understand but just want it to be clear in my head!

Cheers

Lee

[brundles]

I tend to find this site handy when it comes to the likes of that sort of subnet - http://www.subnet-calculator.com

Perhaps I'm mixing things up here, but isn't the WAN IP irrelevant to the subnet? That's the routers job - to shift traffic from one to the other. I would give the routers/firewall the LAN IP of .49 though as the first on the subnet.

And what if the router and firewall are seperate devices?

Not really sure what you are asking, but those settings are for a subnet of 8 addresses - of those, six are usable (.49 to .54) - What devices you use them for is personal preference.

[brundles]

Which one acts as the gateway to the hosts on that subnet?

My network administration is admittedly limited to fairly simplistic setups but in that case wouldn't you want the firewall and router on different subnets with the firewall as the gateway for your subnet and using the router to reach the WAN?

Originally Posted by LSainsbury

What device would I assign to the network address, or what's it purpose?

You dont assign anything to the network address.

OK - so just so I've got this correct - xx.xx.xx.54 is the static IP I assign to the WAN interface from the ISP (the public IP) - what do I then add to the LAN side of the router?

I'm assuming a static IP from the pool of 6 IP's - then the external interface of the firewall device gets the same IP and the internal interface of the firewall gets a 192.168.x.x or whatever.

[Kymmy]

Lee, remember that if you use a modem/router combination with NAT turned on then you will only be able to use a single external IP..

NAT should be turned off and then the router becomes a hub and you can then use each individual external IP... to then use a local network plug in a cable router (one with an ethernet WAN port and use that for local stuff) but for external stuff like servers or external firewalls before a server just plug right into the no-nat modem

Thanks Kymmy - just to confirm I'm talking about ADSL - not cable-based connections.

Understand about the NAT - I have virtualy the same setup here (home) with NAT on the router disabled.

So on the firewall device I have:

Trusted IP, Subnet, Gateway - is the gateway IP the LAN IP of the router?

[Kymmy]

Yep, hence I said router with modem (such things are not allowed on VM cable )

To use all 5 IP's you need a modem attached to the network that is running NO NAT otherwise the LAN ports will be isolated from the WAN. Once you set up the modem it then allows you to connect via the LAN ports (and any hub attached to said ports) any external device and allocate that device an external IP from your allocation. Just remember that these internal ports are connected directly to the outside world and are not secure at this point)

If you want one of the IP's to serve an internal network (like a router) then you'll need another ethernet router (one without adsl modem) and it's WAN will plug into the NO-NAT router, you'll manually allocate one of your IP's (using the same gateway/subnet as per the modem) and then using NAT on that router you have your internal network.

You can also allocate a block of IP's to a single device (like for example a webserver with a firewall running) so that the server can use more than one IP (via windows this is simply done on the network card IP properties..

---------- Post added at 09:13 ---------- Previous post was at 09:10 ----------

Just out of interest who's the ISP and how much is the package/speed including the block of 8 IP's, also is there any restrictions on it?

Thanks for the info. Starting make sense!

BT - think it's an 8Mb service - no idea of the cost/ restrictions as it's not for me!

[Kymmy]

Ahhh...OK

..but saying that I do have similar setup at home...

ISP called Timico (took over a local company called Twang) last year.

I pay £21 for a block of 5 IP's - 8Mb service (of which I get a sync of just over 2Mb 'cus of the distance from the BT exchange) and monthy cap of 20GB - only found that out recently when I went over the limit and they tried to charge extra. All sorted after a few emails with a credit...

Thinking of changing soon to FastNet - near same deal for a couple of quid extra for 40GB...

[Kymmy]

I hate it when they start putting limits on it, I'd need 100Gb+ with at very least 3 fixed IP's and an upload of at very least 0.7Mb

Seems though I'll probably have to wait another year for ADSL2 round here

Originally Posted by Kymmy

I hate it when they start putting limits on it, I'd need 100Gb+ with at very least 3 fixed IP's and an upload of at very least 0.7Mb

Seems though I'll probably have to wait another year for ADSL2 round here

Yeah - and as usual it's marketed as "Unlimited"*

*FUP / AUP Applies...look at FUP / AUP - 20GB (oe whatever limited) - well that's not unlimited IS IT??!

Somedays I think I'm stil on dial-up around here...