shumifan50
Regular Member
- My Satellite Setup
- 2xDM7025(DVB-S tuner), DM600SPVR, DM800S, DM500S HD, Triax 90cm with MultiBracket 4 sats.
- My Location
- Europe
It seems a lot of people have trouble with setting up networks, so I will try to explain some terminology and their use.
IP address: This is like a street address and uniquely identifies a computer on the network.
Static IP address: A static IP address is assigned to a device when it is set up by the person installing the device. This IP address has to be allocated by a person that controls the network. In your own house it would be you and you can decide what IP address to assign to which device. However, you have to bear in mind that all devices that wish to talk to each other should be on the same subnet (explained below).
Dynamic IP address: A network can automatically control the assignment of IP addresses. This is done by a DHCP server. Each device on the network, that is setup for DHCP, will request an IP address when it is turned on and at intervals thereafter called lease times. This means that it is impossible to know the IP address of a given device at any moment in time without going to some trouble, and then it might change in the next second. This is not very useful when used with dreamboxes.
Subnet: Subnet is what it sounds like, it is a sub network or simplisticly a collection of IP addresses that can communicate with each other directly. The range of addresses is specified through a subnet mask, typically in the home environment it will be 255.255.255.0 where the 255 positions of all devices in the subnet have to match EXACTLY, whereas the '0' position has to be unique for each device. When you need more than 254 devices you can set up more complex subnet masks, but that is not needed here. Address 0 and 255 are reserved and cannot be used for devices.
Switch: A switch is a device that allows the connection of many devices to a physical network. In most homeuse cases it will merely provide a lot of sockets into which many devices can plugged. All devices on a switch need not have the same subnet - this means devices from multiple subnets can be plugged into the same switch, but only devices on the same subnet will be able to communicate with each other. Switches can sometimes have embedded firewalls but normally will not.
Bridge/Router:In the past a bridge had much less functionality than a router. These days they are the same in all but name as far as home users are concerned. A router is a device that allows communication between different subnets, a typical case is between a home network and the internet, but it could also be between multiple subnets in a single home network. The router will typically have an IP address on all networks that it routes between. So in the case of the internet connection, it will have an internet address as well as a home network address. All traffic between different subnets have to pass through a router. Routers typically, these days, have embedded firewalls and packet filtering capabilities.(see below).
DNS: This is a name service that provides a world wide lookup of URLs (like _www.goolge.com) to IP addresses. This is needed as all network traffic is based on IP addresses and not on names. So when you enter a URL the DNS server is contacted to translate the URL to an IP address and then the IP address is used for all communication.
Dynamic DNS or DDNS:
Most service providers dont give out static IP addresses. This makesit impossible to set up a web server or server of any description. The work around is to sign up to a DDNS provider like noip.org. These DDNS providers require that you run a little module on your device that keeps updating their servers with the latest IP address of your domain. They also disallow caching of your IP on any DNS servers so that each request to access your domain has to get the IP from their server. This way the DNS lookup of your IP from your domain name is always correct. Your dreambox has a builtin module to do the updates called inadyn. DDNS access is by the nature of the lookup much slower than when you have a static IP address.
Domain names:A domain name is the a name used to group computers together and has most signicance in how browsers allow navigation between different URLs. The whole process is too complicated to describe here. Domains are used to generate URLs that is used in DNS servers to do the IP lookup. A typical domain name will end in .com, .co.uk, .org, .edu, .tv etc etc. It allows addressing specific server seamlessly by using server.domainname.co.uk or the main entry to the domain as _www.domainame.co.uk, as an example.
Firewall:A firewall is a piece of hardware or software that allows you to set up rules as to what traffic you want to allow into and out of your network. The rules can be simple rules that merely block ports (like port 80 for webserver traffic), or much more complex by actually inspecting the payload of packets. They can also behave in 'stealth' mode by not responding to requests that violate access rules or they can just deny the access, meaning the violator knows the server is there even though it is not accessable - this might lead to more persistent attacks.
Port forwarding:If we have only one IP address on a network (like we typically have on the internet), and we have several devices on our home network, we need to tell the router which internal IP address provides the service for a given port on the internet. Lets say we have 2 servers (A and
and we would like to provide 2 websites, but our service provider gave us only one internet IP address. In this case we can forward port 80 (webserver port normally) to server A and forward port 8080 (a port we picked for our second webser) to port 80 on server B. Now both servers can be accessed from the internet by using the same IP(domain name), but different ports. So the URLs would be something like this:
Server A: _http://www.mydomain.co.uk Note that I dont have to specify a port when I use http to port 80
Server B: _http://www.mydomain.co.uk:8080
Workstation setup:
The following is required when setting up a device on a network:
a. IP address. This can be DHCP or static (see above).
b. Subnet mask. Typically 255.255.255.0
c. Default gateway. This should point at a router to communicate with devices in a different subnet. In the case of the internet it will be the address of the internet router, which in the case of most ADSL modems is built into the the ADSL modem. If you dont wish to go outside your subnet, this entry is optional. In the case of dreamboxes we typically want to connect to the internet, so this entry should be setup to point at the ADSL or cable router.
d. DNS server(s): These are required and have to be set up if you wish to use URLs to access network resources rather than IP addresses. Using URLs is strongly recommended as a device will still be found, even when its IP changes.
The next post outlines an example setup.
IP address: This is like a street address and uniquely identifies a computer on the network.
Static IP address: A static IP address is assigned to a device when it is set up by the person installing the device. This IP address has to be allocated by a person that controls the network. In your own house it would be you and you can decide what IP address to assign to which device. However, you have to bear in mind that all devices that wish to talk to each other should be on the same subnet (explained below).
Dynamic IP address: A network can automatically control the assignment of IP addresses. This is done by a DHCP server. Each device on the network, that is setup for DHCP, will request an IP address when it is turned on and at intervals thereafter called lease times. This means that it is impossible to know the IP address of a given device at any moment in time without going to some trouble, and then it might change in the next second. This is not very useful when used with dreamboxes.
Subnet: Subnet is what it sounds like, it is a sub network or simplisticly a collection of IP addresses that can communicate with each other directly. The range of addresses is specified through a subnet mask, typically in the home environment it will be 255.255.255.0 where the 255 positions of all devices in the subnet have to match EXACTLY, whereas the '0' position has to be unique for each device. When you need more than 254 devices you can set up more complex subnet masks, but that is not needed here. Address 0 and 255 are reserved and cannot be used for devices.
Switch: A switch is a device that allows the connection of many devices to a physical network. In most homeuse cases it will merely provide a lot of sockets into which many devices can plugged. All devices on a switch need not have the same subnet - this means devices from multiple subnets can be plugged into the same switch, but only devices on the same subnet will be able to communicate with each other. Switches can sometimes have embedded firewalls but normally will not.
Bridge/Router:In the past a bridge had much less functionality than a router. These days they are the same in all but name as far as home users are concerned. A router is a device that allows communication between different subnets, a typical case is between a home network and the internet, but it could also be between multiple subnets in a single home network. The router will typically have an IP address on all networks that it routes between. So in the case of the internet connection, it will have an internet address as well as a home network address. All traffic between different subnets have to pass through a router. Routers typically, these days, have embedded firewalls and packet filtering capabilities.(see below).
DNS: This is a name service that provides a world wide lookup of URLs (like _www.goolge.com) to IP addresses. This is needed as all network traffic is based on IP addresses and not on names. So when you enter a URL the DNS server is contacted to translate the URL to an IP address and then the IP address is used for all communication.
Dynamic DNS or DDNS:
Most service providers dont give out static IP addresses. This makesit impossible to set up a web server or server of any description. The work around is to sign up to a DDNS provider like noip.org. These DDNS providers require that you run a little module on your device that keeps updating their servers with the latest IP address of your domain. They also disallow caching of your IP on any DNS servers so that each request to access your domain has to get the IP from their server. This way the DNS lookup of your IP from your domain name is always correct. Your dreambox has a builtin module to do the updates called inadyn. DDNS access is by the nature of the lookup much slower than when you have a static IP address.
Domain names:A domain name is the a name used to group computers together and has most signicance in how browsers allow navigation between different URLs. The whole process is too complicated to describe here. Domains are used to generate URLs that is used in DNS servers to do the IP lookup. A typical domain name will end in .com, .co.uk, .org, .edu, .tv etc etc. It allows addressing specific server seamlessly by using server.domainname.co.uk or the main entry to the domain as _www.domainame.co.uk, as an example.
Firewall:A firewall is a piece of hardware or software that allows you to set up rules as to what traffic you want to allow into and out of your network. The rules can be simple rules that merely block ports (like port 80 for webserver traffic), or much more complex by actually inspecting the payload of packets. They can also behave in 'stealth' mode by not responding to requests that violate access rules or they can just deny the access, meaning the violator knows the server is there even though it is not accessable - this might lead to more persistent attacks.
Port forwarding:If we have only one IP address on a network (like we typically have on the internet), and we have several devices on our home network, we need to tell the router which internal IP address provides the service for a given port on the internet. Lets say we have 2 servers (A and
and we would like to provide 2 websites, but our service provider gave us only one internet IP address. In this case we can forward port 80 (webserver port normally) to server A and forward port 8080 (a port we picked for our second webser) to port 80 on server B. Now both servers can be accessed from the internet by using the same IP(domain name), but different ports. So the URLs would be something like this:Server A: _http://www.mydomain.co.uk Note that I dont have to specify a port when I use http to port 80
Server B: _http://www.mydomain.co.uk:8080
Workstation setup:
The following is required when setting up a device on a network:
a. IP address. This can be DHCP or static (see above).
b. Subnet mask. Typically 255.255.255.0
c. Default gateway. This should point at a router to communicate with devices in a different subnet. In the case of the internet it will be the address of the internet router, which in the case of most ADSL modems is built into the the ADSL modem. If you dont wish to go outside your subnet, this entry is optional. In the case of dreamboxes we typically want to connect to the internet, so this entry should be setup to point at the ADSL or cable router.
d. DNS server(s): These are required and have to be set up if you wish to use URLs to access network resources rather than IP addresses. Using URLs is strongly recommended as a device will still be found, even when its IP changes.
The next post outlines an example setup.
