NOOB question : What is the default gateway used for?

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11th October 2011, 01:08 PM
kennysarmy

NOOB question : What is the default gateway used for?

Our IP range is say 25.10.40.0 - 25.10.43.254 - 1024 addresses as given out by RM on the SWGfL.

We have a flat network in which clients are given an IP via DHCP.
Servers/printers/switches etc all have static IP's and are excluded from the range.

DHCP option 003 is set to give the ip of the "default gateway" of 25.10.43.254

When setting up fixed IP devices such as printers/switches we enter the default gateway address of 25.10.43.254

For web browsing a GPO sets the proxy of IE to the IP address and port of our RM Smartcache device.

Question?

What need is there for the "gateway" address to be issued out via DHCP or indeed to enter it manually to fixed IP devices....what does it do or enable them to do?

My background is civil engineering NOT i.t. so sometimes find my fundamental knowledge a bit lacking :(
11th October 2011, 01:13 PM
budgester

The default gateway is an address that will allow a device to connect to other IP address outside of it's own network range. This could be to gain access to a website, ftp, ssh, or access to another vlan on your network.
11th October 2011, 01:14 PM
Geoff

If the machine needs to talk to an IP address that is not in your local ip range it will send the data to the default gateway under the assumption it knows what to do with it. Generally you can consider the default gateway as a 'last resort' by the machine if it can't figure out a better way to talk to the IP it wants to.
11th October 2011, 01:14 PM
TheLibrarian

It can be left blank; it depends on how your clients access the Internet / other networks / subnets.

Essentially it is the address of the router (if one is needed).
11th October 2011, 01:15 PM
Michael

A Gateway is the edge of your network, allowing it to connect to other networks even if they're in a totally different range. Typically your Gateway is a router and this typically has a firewall giving access to the World Wide Web. The biggest network in the world.

The whole purpose of specifying the Gateway IP on many devices can be do with management or firmware updating for example. Without a Gateway, a device couldn't talk to anything outside of your own network.
11th October 2011, 01:16 PM
jjoe90

As above,
If you think of a home network, you have your 192.168.1.1-255 address, "Usually", typically the default gate way is 192.168.1.1 This is the IP of the router that sits next to your phone line, in your front room.

So lets say you have two pcs, one upstaris and one down, to keep it simple upstairs is 192.168.1.2 and down stairs is 1.3 if these computers wish to access the internet then they must communicate with the default gateway which is the router, and the routers IP is 192.168.1.1, so in lamense terms, for computers in your house to access anything out side, they must go through the "GATE" 192.168.1.1
11th October 2011, 01:17 PM
budgester

Basically if a device is trying to connect to a resource, it will see if it is in the same address range, if not, then the IP packet is sent to default gateway address, this will likely be a router or firewall of some sort. Which will then try and forward the IP packet onto a network that does have the IP address that you are looking for.

Quite a good animation/movie is here... Warriors of the Net give it a try, it was used on my Open University CCNA course.
11th October 2011, 01:49 PM
kennysarmy

Quote:

Originally Posted by TheLibrarian

It can be left blank; it depends on how your clients access the Internet / other networks / subnets.

Essentially it is the address of the router (if one is needed).

But our clients all access the internet via a proxy (smartcache) on site with address : 25.10.43.159 operating on port 8080

Quote:

Originally Posted by budgester

The default gateway is an address that will allow a device to connect to other IP address outside of it's own network range. This could be to gain access to a website, ftp, ssh, or access to another vlan on your network.

Does nt sound ideal that I have "devices" which are gaining access outside my network via the router - is there anyway of knowing what is using this route?

The router/firewall is provided to us (again) by RM or SWGfL...so I don't have any management/config. options to it....

What I was thinking of doing was changing the default gateway in DHCP to the ip address of the smartcache and NOT the router....
Will this be more secure?
Fixed items like switches can keep the existing default gateway but computers/laptops will get the ip of the smartcache as that is where all web-traffic should go.

Have I missed anything?
11th October 2011, 01:52 PM
FN-GM

Doing that could break access to anything you might use from the LEA that is not internet based. For example do you access a school wide Intranet? Do you have any services hosted with the LEA?
11th October 2011, 02:18 PM
kennysarmy

No school wide intranet....
No LEA hosted services - our VLE is hosted internally (Moodle)
We have our own internal mail server which obviously has fixed IP.

I could pick a couple of existing PC's and change them to static IP's with the new gateway addrees in place, one classroom and one admin based and see if the users report any issues....
11th October 2011, 02:27 PM
Geoff

web proxys work above the network stack at the application level, the gateway address is only involved if the web proxy isn't on your local network (for example you use a central LEA proxy server instead of one inside the school).
11th October 2011, 02:49 PM
kennysarmy

Quote:

Originally Posted by Geoff

web proxys work above the network stack at the application level, the gateway address is only involved if the web proxy isn't on your local network (for example you use a central LEA proxy server instead of one inside the school).

I see.....so before we had the smartcache as an on site proxy we used to use a remote one...say schoolname.county.sch.uk on port 8080 are you saying if back then if the default gateway had nt been set - internet access would have failed because the PC's could nt have routed out to it? even though the proxy was still set via a GPO?
11th October 2011, 02:52 PM
sparkeh

Quote:

Originally Posted by kennysarmy

I see.....so before we had the smartcache as an on site proxy we used to use a remote one...say schoolname.county.sch.uk on port 8080 are you saying if back then if the default gateway had nt been set - internet access would have failed because the PC's could nt have routed out to it? even though the proxy was still set via a GPO?

Well, even though the proxy was set by gpo, the machines still need to know how to route to it. If the proxy was hosted somewhere outside your network then the gateway is used to route on to that proxy.
11th October 2011, 03:02 PM
kennysarmy

Quote:

Originally Posted by sparkeh

Well, even though the proxy was set by gpo, the machines still need to know how to route to it. If the proxy was hosted somewhere outside your network then the gateway is used to route on to that proxy.

...and now that the smartcache/proxy is internal - it is the smartcache that is passing the web-traffic on to the default gateway....
I've checked the smartcache and indeed there is an entry in the config. for the default gateway...

I suspect then that changing the default gateway for the clients will have no effect on functionality....

However what would happen if I do not set the proxy details in Internet Explorer but DO change the default gateway to the IP of the smartcache - will it then route web traffic correctly?