Monthly Archives: October 2016

Networking With Fiber Cables

Fiber cables form one of the most important parts of the networking industry today. Fiber cables are composed of one or more transparent optical fibers enclosed in a protective covering and strength members. Fiber cables are used to transmit data by the mode of light. Various types of fiber cables available are multimode duplex fiber cables, single mode simplex fiber cables, single mode duplex fiber cables, and plastic optical fiber cables.

There are many fiber optic cable manufacturers who manufacture full line of fiber cables in both single mode and multi-mode, simples, duplex and multi-strand. Several manufacturers provide low cost, quick-turn, high volume fiber cables and fiber cable assembly solutions.

Cables with complete assembly of fibers, strength members and jacket refer to fiber cables. These fiber cables come in variety of forms depending upon their usability and place of use. It is important to identify the exact requirement of fiber cables whether they would be easy to install, splice or terminate, etc. This is necessary as it ultimately decides the cost of installing the fiber cables.

Fiber cables are required to protect fibers from external hazards. Thus before installing the fiber cables one should always assess the place of installation of fiber cables. Fiber cables required inside the house or a building are not exposed too much of hazardous condition thus simpler form and not-so-tough fiber cables can be used for installation. But if the fiber cables are to be installed for longer distances and outside premises then the cables should be robust. They should also be installed well beneath the ground to protect them not only from ground digging, water logging but also from prairie dogs.

Fiber cables comes in different types based on their usage patterns as well. The zip cord and simplex fiber cables refer to those used for desktop connections. Simplex fiber cables are one fiber, tight-buffered and jacketed. A zip cord is actually two simplex fiber cables joined by a thin web. On the other hand fiber cables made of several simplex cables are breakout fiber cables. This type of fiber cables is strong, rugged and larger. They are also a bit expensive but prove to be economic where distances are not too long and fiber count required is less.

Small fiber cables required for dry conduit run, riser or plenum are known as a distribution fiber cables that needs a breakout –box to be broken up or terminated in a panel box. They contain several tight-buffered fibers bundled under same jacket.

Aerial fiber cables are good enough for outside installation where as armored fiber cables are used for under-ground wiring where rodents are a problem. These fiber cables have metal armoring between two jackets to prevent rodents from tampering the cabling connections.

Loose tube fiber cables are perfect for plant trunk applications to prevent fibers from moisture or water. They can be buried directly in ground but must be handled carefully to prevent damage. Ribbon fiber cables have twelve or more fiber cables packed together laid in a rows. They are also a plant fiber cables which are gel-filled and are good for water blocking.

All fiber cable manufacturers manufacture different fiber cables but their product literatures should be carefully studied so as to assess which type of fiber cables they specialize in.

Finding Your MAC Address On Wired And Wireless Network Cards

The Answer To The Media Access Control Question
Over the past few weeks I have received quite a few e-mails about Ethernet cards, both wired and wireless, and more specifically, about Media Access Control (MAC) addresses. I think the main reason I’ve received so many questions about Ethernet cards and MAC addresses is people trying to secure their home wireless networks and their desire to use MAC address filtering. This type of filtering in wireless networks can be configured to allow or deny specific computers to use or attach to the wireless network, based on the MAC address.

My first thought was to write an article just about MAC addresses and wireless Ethernet. After thinking about it I decided to expand on this and go over some specific information about Ethernet cards and communication.

Different Ways Of Finding Your MAC Address And More
There are several ways of finding your Ethernet and communications protocol information. Many Ethernet card manufacturer’s have proprietary software that can reveal this information but they work differently depending on the manufacturer. So we will use the Windows 2000 and XP “ipconfig” utility since this is available in the majority of Windows Operating Systems.

First, go to “start” -> “run” and type “cmd” without the quotes. Then hit the enter key. At the command line type “ipconfig /all”, again without the quotes. Actually, just typing ipconfig without the /all will work but will only provide you with abbreviated information regarding your network cards. An example of what you might see by typing the “ipconfig /all” command is below with each item commented in green lettering:

Fault Tolerant And Highly Availability Computer Systems
There are several ways of finding your Ethernet and communications protocol information. Many Ethernet card manufacturer’s have proprietary software that can reveal this information but they work differently depending on the manufacturer. So we will use the Windows 2000 and XP “ipconfig” utility since this is available in the majority of Windows Operating Systems.

First, go to “start” -> “run” and type “cmd” without the quotes. Then hit the enter key. At the command line type “ipconfig /all”, again without the quotes. Actually, just typing ipconfig without the /all will work but will only provide you with abbreviated information regarding your network cards. An example of what you might see by typing the “ipconfig /all” command is below:

OutPut Of The “Ipconfig /All” Command
Windows IP Configuration

Host Name . . . . . . . . . . . . : Home Computer
This is the name of your computer, typically defined during the windows installation. However, it can be changed after installation.

Primary Dns Suffix . . . . . . . :
If your computer participates in a network such as a Microsoft Windows domain this item may contain the name of the domain.

Node Type . . . . . . . . . . . . : Unknown
The Node Type may say Unknown, or peer-to-peer, or in some cases “hybrid”. It is a setting that has to do with the Windows Internet Naming Services used in certain types of Windows domain networks.

IP Routing Enabled. . . . . . . . : No
This setting determines if Windows XP or 2000 will function as an IP router. If you have two or more network cards you can setup your system to act as a router, forwarding communications requests from one network to another. Windows 2000 can be configured to do this in a pretty straight forward fashion; Windows XP will need a registry modification.

WINS Proxy Enabled. . . . . . . . : No
WINS Proxy is another setting that is related to the “Node Type” we discussed earlier. It is normally not a required setting in a home or small office network, or newer types of Microsoft Windows domains.

Ethernet adapter Wireless Network Connection 2:
If you have multiple Ethernet (network) cards in your systems, as I do in this laptop, you will have multiple listings. This one happens to be the second Ethernet card, an internal wireless Ethernet card.

Description . . . . . . . . . . . : Broadcom 802.11b/g WLAN
This is the description of the Ethernet card, usually the Name / Manufacturer and type of Ethernet card. In this case, it is a Broadcom wireless Ethernet card built into my laptop.

Physical Address. . . . . . . . . : 00-90-4B-F1-6E-4A
And here we have the MAC address. The MAC address is a 48 bit hexadecimal code and is suppose to be a totally unique address. It is 48 bits because each number or letter in hexadecimal represents 8 bits. Hexadecimal numbers range from 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E, F. There are 6 alpha-numeric codes hence 6*8=48(bits). The first 3 codes identify the manufacturer of the card and the remaining codes are used to create a unique number. Theoretically there should never be a card with same MAC address on a local network. However, there are a few exceptions. There are software tools that allow you to change this code. In fact, this is a step some hackers take to attack other systems on a local network. I say local network because MAC addresses are not routable between network segments. By spoofing this address, you can impersonate another machine on the local network. Traffic that was bound for the intended target can be redirected to the hacker’s machine. This is the address you would also use to populate a MAC address, or physical address table when setting up your wireless access point to support MAC address filtering.

DHCP Enabled. . . . . . . . . . . : Yes
DHCP, or the Dynamic Host Control Protocol, if enabled means your computers IP address is being provided by a DHCP server on you network. The DHCP server could be your wireless access point, cable/dsl router, cable modem, or a server on your network. Also, if a DHCP server is not enabled on your network, your computers Operating System will auto generate a random IP address within a certain predefined range. This means you could network a group of systems together without having to manually assign the IP settings.

IP Address. . . . . . . . . . . . :
This parameter provides you with your current IP address. The address listed above is what is called a “private” address. There are certain classes of IP addresses that have been set aside for private use. This means for your internal, local, or private network at home or office. These addresses are not, or should not, be routable on the Internet. The Internet routes what are called “valid” IP addresses. Your cable/dsl router or cable modem has a valid IP address assigned to its “external” network interface. The external interface may be your phone line or cable TV cable.

Subnet Mask . . . . . . . . . . . :
The Subnet Mask is a special number, or in some sense, filter, that breaks down your IP address, in this case private IP address, into certain groups. IP addresses and Subnet Masks can be a complicated matter and would take an entire article to go over.

Default Gateway . . . . . . . . . :
The default gateway, the IP addresses listed above, is the IP address of the device that will route your request, such as when you try to browse a website, to the Internet. It is a bit more complicated than that though as gateways or routers can route traffic to various different networks, even other private networks. At your home or small office, this gateway most likely is your cable/dsl modem or router.

DHCP Server . . . . . . . . . . . :
The DHCP server, remember we talked a little about this above, is the device that assigns your computer an IP address and other information. DHCP servers can assign all kinds of information such as; Default Gateway, Domain Name Servers (DNS), IP address, Subnet Mask, Time Server, and much more.

DNS Servers . . . . . . . . . . . :,
DNS Servers are internal or external servers that resolve Fully Qualified Domain Names (FQDN), such as , to IP addresses. This is done because computers don’t actually transmit your requests using the domain name, they use the IP address assigned to the FQDN. For most home or small office users, the primary DNS server is the IP address of your cable/dsl router. Your cable/dsl router than queries an external DNS server on the Internet to perform the actual resolution of the FQDN to IP address. The address is an internal private device on my network whereas the is an external public Internet DNS server and is present just in case my router has trouble performing the DNS resolution tasks.

Lease Obtained. . . . . . . . . . : Sunday, March 19, 2006 6:38:16 PM
This information tells you when your computer received its IP address and other information from a DHCP server. You will notice it says “Lease Obtained”, that is because most DHCP servers only lease the IP address to you from a pool of available address. For instance, your pool may be through So your DHCP server has 50 IP addresses to choose from when assigning your computer its IP address.

Lease Expires . . . . . . . . . . : Wednesday, March 29, 2006 9:38:16 PM
When the IP address, assigned by the DHCP server, lease expires it will attempt to lease you the same or another IP address. This function can typically be changed on the DHCP server. For instance, on some fully functional DHCP servers, you can configure the Lease to never expire, or to expire within 1 day and so on.

Why Are MAC Addresses So Important And How Do They Work
To jump back to MAC address for just a bit. You may think that IP addresses are the most important thing when it comes to network communication. The reality is, MAC addresses are very  important because without them computers would not be able to communicate over Ethernet networks. When a computer wants to speak with another computer on a local network, it will make a broadcast request, or ask a question, of who owns a particular IP address. For instance, your computer may say “Who is”. Using the information above, my default gateway is and will answer “I am “00-90-4B-F1-6E-4A””. It sends back its MAC address. That MAC address then goes into what is called a Address Resolution Protocol (ARP) table on your computer. You can see this information by going to the command prompt like you did above and typing “arp –a”. You will get information like the following:

Internet Address Physical Address Type 00-12-17-5c-a2-27 dynamic 00-12-17-5c-a2-27 dynamic 00-0c-76-93-94-b2 dynamic 00-0e-2e-2e-15-61 dynamic

How A Hacker Can Use MAC Addresses In An Attack
You will notice the IP addresses and to the right of them the MAC addresses. Without this information, without the MAC address, you would not be reading this article right now. MAC addresses are not routable like IP addresses. They work on your local or private network. However, devices on the Internet perform the same tasks. Routers and switches maintain a list of their peer devices MAC address just like your computers and devices on your home or office network. I mentioned above that MAC addresses can be changed in order to redirect requests. For instance, if I were on your office network and you had an internal web server that took personal information as input, I could tell your computer to go to my laptop for the web site by broadcasting my MAC address tied to the real web servers IP address. I would do this when you computer asked “Who is the “Real Web Server””. I could setup a fake web server that looks just like the real thing, and start collecting information the real web server would normally collect. You can see how dangerous this can be.

There are several other easy ways you can find your MAC address but they can be a little confusing if you have more than one internal network card. Most external USB, or PCMCIA wired and wireless Ethernet cards have their MAC address printed on them. In cases where the wired or wireless network card are inside your computer, such as in laptops, the MAC address is sometimes printed on the bottom of the laptop. Even Desktop systems cards that are inserted in PCI slots have the MAC address printed on the Ethernet card.

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