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General Ethernet LAN FAQ - 7/11/08

Last response: in Networking
June 17, 2010 5:00:01 AM

General EthernetLAN FAQ

What does the Uplink feature on a router, hub, or switch do?

10/100 BaseT Ethernet jacks contain two signals, Receive (Rx) and Transmit (Tx), each of which is made up of two twisted-pair wires.
An uplink port on a hub, switch, router, or any other network device, is simply an Ethernet port where the Receive and Transmit signals are swapped. This lets the Transmit signal on one device, correctly connect to the Receive connection on the other device (and vice-versa). This allows you to expand the number of ports on your hub, switch, or router.The Uplink feature can be implemented by a dedicated port, shared port, Normal/Uplink switch, or a feature known as auto MDI / MDI-X. This feature, available on some newer devices, automatically figures out how connect with whatever is plugged into it. Very handy, especially for novice networkers!
NOTE! On devices with a shared uplink port (usually indicated by some sort of graphic such as a line between the two ports), never plug something into both the normal and shared uplink port at the same time. This will cause strange problems that will take you a long time to figure out! If you're not sure whether your uplink port is shared, assume it is and if you're using it, don't plug anything into the port that is located right next to it.

Can a router be connected directly to an Ethernet switch?

In general, any make of router can be connected to any make of switch or hub in order to expand the number of Ethernet devices connected to it.
The simplest way is for one of the devices to have Uplink capability. All you do is use a normal Ethernet patch cable, plug one end into the Uplink port (which can be on either device), and the other end into a Normal port on the other device. If both devices have Uplink ports do not connect Uplink port to Uplink port!
If neither device has Uplink capability, you'll need to get or make a crossover cable, and plug it into any port on each device. See for an article for details on how to make a crossover cable.

What is the difference between a switch and a router?
The simple answer is that a router (which usually includes a built-in switch) allows you to connect multiple computers into a network (via the switch part) and share a single Internet connection among multiple computers (via the router part). A plain switch will only connect multiple computers into a network.
Note that you can expand the number of devices that can connect to a router/switch by buying another switch and connecting the devices together. See the other topics this FAQ section for more info on how this is done.
Internally, how does a hub or switch swap the TX and RX signals?
It performs this magic by simply changing the connector pins that the signals are wired to.

What's the difference between a router and a hub?
Basically, the same as between a router and a switch.

What is a 1394 Net Adaptor Connection and why does it appear in my WinXP Network Connections?
That's WinXP's way of telling you that you have an IEEE 1394 interface installed in your system. IEEE 1394 is more commonly known as Firewire and can be used to network two Firewire-equipped systems together, in addition to its ability to connect to peripherals such as digital cameras, camcorders, and external hard drives.
Since Firewire has a 15ft cable length limitation, its networking uses are limited to quick system-to-system connections for file transfer purposes, running at speeds between 12.5 to 50Mbps.

Can I hook up two computers that both have Ethernet adapters without using a hub, switch, or router?
Yes. You'll need to use a special cable called a "crossover" cable, however, or the two systems won't be able to communicate.
The "crossover" cable looks like a normal UTP Ethernet cable, but it's wired differently, swapping the Receive and Transmit Ethernet signal pairs.
Be sure to Enable File and Printer sharing in both systems' Network Control panels and we suggest using the NetBEUI protocol to get you up and running quickly.

How can I easily switch my laptop between home and office network settings?
Easiest way is to get the settings from a DHCP server at both locations. All you need to do is set your TCP/IP properties to "Obtain an IP address automatically", and maybe do a DHCP Release / Renew or an WinXP connection Repair after you connect up at each location.
But assuming that you have to use manual settings for at least one location, you have a few other options:
• If you have WindowsXP, and you're switching between just two networks, you can use the Alternate Configuration tab of your network adapter's TCP/IP properties. To reach this setting, open Network Connections, right click on your network adapter's icon and select Properties. Scroll down the "This connection uses the following items:" box in the General properties tab and click on Internet Protocol (TCP/IP) to select it, then click the Properties button. You'll see the Alternate Configuration tab in the properties window that opens.
• If you're using another operating system, a popular (but pay-for) option is NetSwitcher, which costs $14 and supports more than two network configuration.

How do I release and renew an IP address in WinXP?

One of the steps forward that WinXP took was to simplify the task of fixing broken network connections. A DHCP Release/Renew is part of what's done by clicking the Repair button in the Local Area Connection Status window for your computer's LAN connection.
You get there via Start Settings Network Connections, then double clicking on either the Local Area Connection or Wireless Network Connection icon in the LAN or High-Speed Internet portion of the Network Connections window. Once the Status window opens, click on the Support tab, then click the Repair button.
This button performs a number of other handy connection-repair tasks too, which are described in this;en-us;Q289256 Microsoft Support Bulletin.

What are the prefered network protocols to use in a small LAN?
All you really need to run is TCP/IP. It is required for Internet access, but will also handle File and Printer sharing just fine. TCP/IP is the protocol used by default by WindowsXP, which has built-in configuration routines that make setting it up fairly painless.

Do internal modems have MAC addresses?

No. Only IEEE802.3 hardware interfaces (often called 'ethernet', though technically different) have a MAC address. A dial-up modem typically uses ppp, an IETF-specified means of implementing the upper layers (TCP/IP) on a modem connection which does not use IEEE802.3 hardware.
Similarly, a cable modem uses a non-802.3 hardware interface on the cable-side connection and therefore has no MAC address on that interface. MAC is only for physical layer IEEE802.3-compliant hardware interfaces.

have a small Ethernet network based around a hardware router. Can I use a second router to expand the network?
You certainly don't need a router to connect more computers to your network--just a switch or hub uplinked into one of the router's ports will do. But if you have an old router with built-in switch lying around, all you need to do is shut off its built-in DHCP server and set its IP address so that it's in the same Class C range as the addresses being served by the main router, but outside its DHCP server range.
For example, if your main router has an address of and its DHCP server is set to lease addresses from to, set the "retired" router to
Make sure you use only the "retired" router's LAN ports for connecting your additional computers. You'll also need to use one of the "retired" router's LAN ports to connect to one of your main router's ports. Use a crossover cable to do this unless one of the routers has uplink capability.
If the "retired" router has a built-in print server, you can still use it, too. You'll be able to reach it at the new IP address that you've assigned to ol' faithful.

When I connect two computers via Firewire (1394 Net Adaptor), how do I see the other computer that I'm connected to?
You would look for the other computer in My Network Places, as you would any other network connection. Note that you may have to use Windows' Search to find the other computer the first time. You can also click Start, then Run, then type in <icomputername</i where <icomputername</i is the name of the computer you want to connect to.

Can standard coax cable be used to carry a network connection (i.e, can I connect my Ethernet cable to coax which is already throughout the house)?
Yes. "Corinex' CableLAN series of products will work with coax networks intended for TV signal distribution and with or without TV signals on the same cable.
Products with similar capabilities should also appear during 2006 that are"MoCA (Multimedia over Coax) compliant.

How can I connect a USB-only printer to the parallel port on my network router or print server?
Unfortunately you can't. Although there are converters that will let you connect a parallel-port printer to a USB port, there are none that go the other way.

If you have a network of 10-15 clients and 4-6 servers, would it best to have all those devices on one switch?
It all depends on the volume and pattern of network traffic. The key is understanding the data flow between clients and servers. Most current-design switches are designed to be "wire speed" and non-blocking. This means that they will support the rated per-port speed simultaneously for all port pairs. In other words, in a 24 port 10/100 switch, you can have 12 pairs of computers simultaneously transferring data at 200Mbps full-duplex. This is probably fine for client-to-client transfers and would let you connect all clients to one large switch.
Servers, however, may have different requirements. Data flow to and from a busy server might easily exceed the 200Mbps available from a 10/100 switch port. Fortunately, many larger switches have gigabit Ethernet uplink ports that are just the ticket for solving this problem. All you need to do is put all servers—or just the busiest ones—on their own 10/100/1000 switch and connect it to the client switch(es) via its 10/100/1000 uplink port. With prices for gigabit-equipped switches in rapid decline, you might even choose to skip the data-flow analysis and just go for it! If you need a little convincing, Intel has some"case studies that may help you decide.

What is the best way to back-up PCs over a home network?

The "best way" in our opinion is to have the process be as automatic as possible, especially if you're dealing with non-technical users. Installing and running a program like,aid..."PowerQuest's Datakeeper or"Centered Systems' SecondCopy will automatically copy new or modified files to another folder, local or remote hard drive, or removable storage device.
The easiest way to go with one of these solutions is to use another system's hard drive for the backup, especially if you have a number of systems, a lot of data, or both to back up! You can then back up that single drive to removable media, which can be stored in a fire-proof box or preferably off-site. Your choice of media will be mainly dictated by the size of the backup and personal preference.

How do I connect more than 10 computers to a W2K or XP Pro machine?
Unfortunately, this limit on the number of allowed inbound network connections is set at 10 for WinNT, Win2000, and XP Pro, 5 for WinXP Home, and can't be changed.
However, there is a 15 minute Autodisconnect for idle network connections that can be changed. See"this Microsoft KnowledgeBase article for instructions on how to change the AutoDisconnect time in WindowsXP and;EN-US;122920"this article for WinNT and 2000.
If you need more than 10 simultaneous connections to a single computer, you have the following choices:

* Run Windows 98 on that machine. Although it's hard to find definitive information, users have reported being able to make up to 20 or so simultaneous network connections to a Win98 machine.
* Use a Microsoft server OS on that machine
* Purchase a Networked Attached Storage device such as"any of those reviewed on TomsNetworking, or others that are Linux based and don't have limitations on the number of network connections
* Run a Linux-based server and use SAMBA to share files with Windows clients

Are there Dynamic DNS services that allow running your own DNS servers?
TZO says its"DNS forwarding service allows you to run your own DNS server and manage the DNS records for the sub-domains of your own domain.

Is the number of ports on a router equal to the number of clients that it will support?
No. The number of physical ports has nothing to do with the number of computers that are supported. The number of supported clients is typically a maximum of 254.
Some wireless routers support only 32 wireless clients, but still support a total of 254 computers.
See 166"this FAQ for help on expanding the number of physical ports on your router.

What is the Macintosh equivalent of Windows ipconfig /release & renew?
There is no direct equivalent, but a couple of ways to proceed. We'll describe just one here.
For pre-OS X versions, you'll need to use the TCP/IP Control Panel. For MacOS X you'll need to get to the System Preferences Network Control Panel and TCP/IP tab.
Once you're at the correct Control Panel, you'll need to change the Configure setting from "Using DHCP Server" or "Using DHCP" to "Manually" temporarily. (You may need to enter IP address information temporarily if you get a pop-up complaint.) After you make the changes, quit the Control Panel (saving when prompted), or for OS X, click the "Apply Now" button.
Now just repeat the same steps, changing the Configure setting back to "Using DHCP Server" or "Using DHCP". If you need a detailed walk-through,"see this article, or"this one.

How many switches can be connected together?
As many as needed. The"5-4-3 rule in networks applies only to older networks that use hubs (repeaters). Be sure, however, to observe the maximum cable length of 100Meters for any port-to-port connection.
Note also that multiple ports on a switch can be used for "uplinking" by using crossover cables, or by using the uplink capability on the switches that are being connected to the main switch.

What are the rules for setting IP addresses for network bridge devices?
Since bridges link physically separated parts of the same network, bridges must be assigned addresses in the same network segment as the devices they connect.
For example, if computers in the bridged segments have IP addresses in the 192.168.1.X range, the bridge devices would also be assigned in that range.
We recommend assigning static IP addresses to any network infrastructure devices. Make sure the addresses are outside the range of addresses assigned by your LAN's DHCP server.

Should there be a difference in LAN-only file transfers when using a router vs. a switch?
Since client-to-client communications all occur on the LAN side of a router using"private IP addresses, the routing "engine" should not be involved in the transfer. So there should be no speed difference between the two methods—all other factors being the same.
Speed differences could occur due to differences in the switch chip used, and particularly due to differences in auto-negotiation of speed and link type. These factors, unfortunately, can't be controlled in most consumer routers and switches. It's also possible that the router is either trying to do a DNS lookup on LAN traffic or forwarding it through its default gateway—both of which it should not be doing, and which could slow transfers down significantly.

Is it better to use one or multiple switches to handle many ports?
It depends on the data-flow ("traffic" ) patterns in your network. Any switch you buy today is wire-speed, which means that it can handle the maximum advertised per-port speed between all ports simultaneously. This works well if traffic is evenly spread among ports or consists of mostly small files.
But, in many cases, network clients all want to reach the same server, and may also want to upload and download large files from it. This means that the server connection can become a bottleneck and requires more bandwidth than available from a normal switch port. This is often handled by using switches with gigabit Ethernet (or 10gigabit) uplink ports, which should be able to handle 10 ports running full blast. Networks with many busy servers often move them all to their own gigabit Ethernet switch that has multiple 10/100 switches uplinked via a gigabit Ethernet link.

What is the difference between a Switch and a Hub?
A hub is an,289893,sid9_g..."OSI Layer 1 device that repeats data received at any of its ports to all ports in the device. A switch is a Layer 2 device that uses the MAC address in each data packet to send it only to the port connecting the device the data is intended for.
Switches can improve network speeds in busy networks because they allow full port speed to be used for every pair of devices connected to the switch. Switches have essentially replaced hubs in even consumer networks because chip-level integration has driven the cost difference to essentially nil.
Hubs still are useful, however, when using network analyzers ("sniffers" ) because all network traffic can be viewed at any hub port. Note, however, that using a hub will slow down traffic on a busy network, possibly hiding the problem that is trying to be analyzed.

What is the "default gateway" in my computer or router's IP address information mean?
There are many definitions, but we like this one"from Cisco the best:
<iThe router that all packets are sent to when the sending device does not have the address of the destination device. The default gateway then forwards the incoming packets to other appropriate networks and becomes the static route to the other networks.</i
If a device is set to obtain its IP address information automatically, the proper default gateway address will be supplied along with the leased IP address. Think of it as the "gateway" to the Internet for all the data coming from your network.

What does VLAN capability in a switch or router do for me?
The concept of VLANs originated in the mid 1990's, and unfortunately has evolved to include multiple networking techniques, leading to confusion. VLAN stands for Virtual Local Area Network and, in its broadest definition, is a technique where one or more physical LAN switches deliver packets as if they were a single physical switch.
The simplest VLAN is a physical network switch that can have its physical ports assigned to logical (or virtual) port groupings. Each group behaves as though it were on its own physically separated network, i.e. no communication allowed between groups.
More complex forms of VLANs allow spanning of multiple physical devices (example: some of VLAN A's ports are on switch 1 and some of its ports are on switch 2) and even overlap between VLANs (example: port 1 of a switch is on VLAN A and VLAN B, while port 2 is on VLAN A but not VLAN B).VLANs can be used both for bandwidth / traffic control and also to enhance network security.
[Definition rewritten from John Wobus' Basic Glossary on Campus Networks]
What is a residential gateway?
It's a catch-all marketing term commonly used for consumer routing devices. You'll need to examine a product's features and specifications carefully to know what it does, if anything, in addition to providing Internet sharing and basic firewall protection.

Which is faster, a wired or wireless LAN?
It depends on the technology used. For example, an 802.11g wireless LAN under best-case signal conditions can be faster than a 10BaseT Ethernet LAN.In general, however, a wired LAN will have more consistent performance that doesn't vary with distance or physical obstacles. This consistency is due to the more robust nature of copper wiring (or fiber-optic cable) vs. wireless transmission.

What is auto MDI / MDI-X?
This feature gives an Ethernet port the ability to automatically switch its Receive and Transmit connections to establish connection with whatever is plugged into it.
It essentially gives each port 160""uplink" capability and eliminates the need for using crossover cables when connecting switches together for port expansion.

How do I set up a basic Ethernet network?
We don't have a basic networking tutorial because the subject has been covered so well by so many other sites, that we're happy to just point you in the right direction. Here are our picks for sites that should help get you connected up in a jiffy!"HomeNetHelp's Easy Home Networking Tutorial is very complete, and includes a section to help you decide what kind of network to install." contains most of J. Helmig's old World of Windows Networking site, but has made it tougher to navigate around. The excellent content is still there if you're willing to hunt for it, with coverage of advanced networking topics and most Windows OSes.

Is it possible to plug a USB hub into a print server and use it for multiple printers on that one server?

It depends on whether the print server is designed to handle more than one printer, but generally, no. Single port print servers are generally designed to handle one attached printer.

Can 2 or more computers be connected via USB?
Yes, but you'll need to purchase a special USB to USB cable to do it, such as the "Net-LinQ cable from Parallel Technologies or PPA International's USB 2.0 Datalink / Networking Turbo Link cable"Model 1554.

Is a stand-alone printer server better than one built into a router?
Most print servers built into routers or other consumer networking gear are pretty simple and support the"LPR protocol and generally don't handle bi-directional printer features very well. Stand-alone print servers might support more protocols and have more memory which could help printing speed if you have many users doing a lot of printing. You need to carefully review the specs of the products you are considering.

What is a subnet mask, and how is it used?
If you read through the many definitions of subnet that"Google comes up with, you should get the gist that a subnet is a mechanism that allows network administrators to group devices on a network in order to localize data traffic for both privacy and network traffic control purposes.
A subnet mask is a number in "dotted quad" format (four groups of three decimal digits) that tells network routers which bits of an IP address to look at when deciding where to route a packet of data. The subnet mask that most of us are familiar with allows for a grouping of 253 devices (addresses with all 1's or all 0's are not useable device addresses).
The subnet mask you use is generally determined by how the routing is set up at the level above your LAN, i.e. your ISP. Most small networkers don't have to deal with the calculation of subnet masks unless they want to set up a network with multiple routers and subnets.
More info in this,,s... SearchNetworking definition, 3Com paper (PDF) "Understanding IP Addressing: Everything You Ever Wanted to Know" and Cisco article IP Addressing and Subnetting for New Users.

What features/advantages come with more expensive routers the next level up from SOHO?
With the wide range of features available in consumer-grade NAT routers it's hard to make a generalization. But from what we've seen, there aren't many features the average consumer would need that aren't available in 'consumer' grade routers.
That said, the extra money you pay for 'next level' routers can buy you a better warranty, more knowledgeable tech support and pure routing (not NAT) and management features more suited for use in networks containing multiple routers. But chances are, you'll also be paying for the privilege of having that 'next level' manufacturer's name on the box, too.

How can I verify that my Ethernet network is running at Full-Duplex (20/200Mbps) rather than Half-Duplex (10/100Mbps)?
You'll have to rely on the lights on your NIC and switch in most cases. The speeds reported by Windows' network connection properties do not take into account full-duplex operation.
You can check the Advanced Network properties for your NIC to see if you can force the speed and mode. It's also possible that your network adapter came with a utility that might show how the adapter is actually set up as well as configure it.

Will Mac OS and Windows computers see each other on the network?
It depends on the version of Mac OS. Pre OS X computers will need third-party software such as"Thursby Software's Dave on each Mac. Macs running OS X will be able to share files and printers with Windows computers and "see" Windows machines right in the Finder. OS X Macs will also appear in Network Neighborhood or My Network Places. Note that both the Macs and Windows machines must be using TCP/IP as their networking protocol.

What's the difference between a virtual LAN and VPN?
A Virtual LAN (VLAN) allows computers on physically different LANs to be logically treated as part of the same LAN by using a tag-based software mechanism. Part of each data packet is changed (or tagged) with bits that provide information to VLAN-aware network devices that tell it how to handle the packet.
A VLAN neither encrypts data nor provides authentication for users, but can provide some measure of security by preventing users on a LAN from "seeing" each other by controlling how broadcast traffic is handled.
A Virtual Private Network (VPN) uses encryption and authentication mechanisms to securely transport data through networks. Only authorized users with proper encryption keys may access VPN data.

What is the difference between a Layer 3 switch and a router?
Layer 3 switches are generally enterprise-level devices (,,s...""Layer 3" refers to the OSI model Network layer—switches are Layer 2 devices and hubs are Layer 1). Both routers and Layer 3 switches can direct data packets based on the IP address they contain, but while Layer 3 switches generally can switch only IP-based traffic, enterprise-level routers can handle other protocols such as IPX and AppleTalk.
On the other hand Layer 3 switches are considered to be more efficient than routers at handling IP traffic and also more cost-effective.

How much do 100Mbps Ethernet ports affect the speed of a broadband connection?

It depends on the bandwidth of your connection and the nature of your use. 100Mbps Ethernet on a Windows XP system typically provides around 80Mbps of sustained bandwidth. This is fine for the majority of current U.S. broadband providers, which typically provide only 10-20Mbps of download bandwidth.
But even if your connection bandwidth is measured in the 100's of Mbps, you probably wouldn't notice a limitation from 100Mbps Ethernet unless you were doing long downloads, or had many users on your LAN.
In any case, upgrading to 10/100/1000Mbps Ethernet is simple, inexpensive and definitely worth it if you move a lot of large files around your LAN.

What is the difference between a hub and a residential gateway?
A residential gateway (which is a marketing term for a consumer router) allows allow multiple clients (computers) to share a single Internet connection.
A hub (or a similar device known as a switch) is used to connect multiple Ethernet devices into a Local Area Network (LAN), but provides no Internet sharing function.

What is the difference between a managed and unmanaged switch?
Unmanaged switches have no user interface and therefore no settings that can be changed.
Managed switches have a user interface that allow control of numerous switch functions. Control functions include the ability to enable / disable individual ports, port "mirroring" (copies all data on one port to another port for test / monitoring purposes) and port traffic statistics. Other features include the ability to assign ports to virtual LANs (VLANs), Quality of Service tagging and traffic prioritization and, in some cases, bandwidth control.
Note that managed switches sometimes are called "smart" or "intelligent" switches for marketing purposes.

What are the differences among DSL types?
Similar to the numerous dial-up modem standards, types of DSL differ in the protocols and techniques they use to provide uplink and downlink speeds."This table has a good summary of DSL types, speeds and distance limits.

How do I share a networked printer to two separate networks connected to the Internet via two separate routers?
The easiest way would be to use a dual-WAN router instead of two separate routers, which would put everything on one, big, happy LAN.
You could also set both of the routers' LAN addresses to the same subnet, for example 192.168.3.X, and run a cable between spare ports on both routers. Note that if neither of your routers supports 597"auto MDI / MDI-X, you'll need to use the uplink port on one of the routers when you interconnect them. If you have neither uplink nor auto MDI / MDI-X, then use a crossover cable to interconnect. If you're out of ports on one (or both) routers, you'll need to add switch(es) to get the extra ports you need.
You'll also need to set the admin servers of each router to a different address so that they are both reachable. Then disable the DHCP servers in both routers and manually set the IP address information in each client (and printer). The last step is required so that clients don't get confused by the presence of two DHCP servers and so that they access the Internet via the desired router.

How can I use two network adapters on one machine?
It is possible to use multiple network connections on the same computer. This is commonly done in the server environment, where computers will have internal and external connections (such as a mail server), however it is less common in the home environment. What you are doing is turning your computer into a router, and in many cases, it is easier and cheaper to buy a router/switch.
Why would someone use two network connections on a single machine? LAN Party goers may want to play on the internal network, while downloading a file from the Internet. You can also use a two connection PC as a quick and dirty server or firewall see this article]. With one wireless connection and wired connection, your PC can operate as a wireless hotspot.
If you do decide to use two network connections on the same PC, then you will need to configure the IP Addresses of both connections. Each connection must be on a different subnet. Example would be one card at and the other at Then you have to assign preferred routes in the Operating System. In Windows this is done with either the command line ROUTE ADD command or by going to the advanced TCP/IP Network Properties in your network connection.

I have a problem on my personal network where the DHCP lease is too short. What sets the length of the DHCP lease?
Most LANs that use a router to connect to the Internet use the DHCP server in the router. Some routers allow the lease time to be changed, but others don't.
If you have a single computer connected to a cable, DSL or other broadband modem, your DHCP lease time will be determined by your ISP.
Note that some wireless access points and NAS devices also contain embedded DHCP servers. Make sure that only one DHCP server is enabled on your network (preferably the one in your router), or you might experience network connectivity problems.