Connecting the Cisco IP phone 7940G

The inbuilt Cisco two-port Ethernet switch allows for a direct connection of the IP phone to a 10/100BASE-T Ethernet network via an RJ-45 interface. A single LAN connection will be enough for both the phone and a nearby PC.

The system administrator can designate separate virtual LANs (VLANs) for the PC and Cisco IP Phones providing improved security and reliability of voice and data traffic.

The Cisco IP Phone 7940G can also receive power down the LAN from any of the Cisco inline power-capable blades and boxes

Network Requirements
.The network must have a working VOIP network, which means Voice over IP (VoIP) configured on your Cisco routers and gateways
. Cisco CallManager* Release 3.0 or higher installed in your network and configured to handle call processing
. IP network that supports DHCP or manual assignment of IP address, gateway, and subnet mask

Adding a Cisco IP Phone Using Cisco CallManager
The IP phone has to be added to the CallManager before we can actually use it. This is done with Cisco CallManager Administration using either auto-registration or without auto-registration.

Auto-registration allows you to automatically add Cisco IP Phones to Cisco CallManager Administration simply by plugging them into a Cisco CallManager network. Auto-registration automatically assigns a directory number (selected from a range of numbers) to the telephone.

By default, auto-registration is turned off. When Cisco CallManager Administration is configured, you can turn on auto-registration by specifying a range of numbers from which auto-registration can choose directory numbers. Then, when new phones are added, they are automatically assigned the next available directory number. If a phone is moved to a new location, its phone number does not change.

Turning on Auto-Registration:
.Open Cisco CallManager Administration.
.Click Configuration.
.In the Auto-Registration area, click Configure. Type the start and end directory numbers (provided by the telephone company).
.Click Update. (The range of directory numbers auto-registration can use is configured, and auto-registration is enabled. When a new phone is added to the system, its directory number is automatically assigned by auto-registration).

Turning auto-registration off prevents unauthorized devices from registering with and gaining access to the Cisco CallManager.

Turning off Auto-Registration:
.Open Cisco CallManager Administration.
.Click Configuration.
. In the Auto-Registration area, click Configure. ( Type the same directory number in both the start number and end number boxes. For example, type 1000 as the start number, and 1000 as the end number).
.Click Update.( Auto-registration is turned off. New phones added to the system must be manually configured in Cisco CallManager Administration).


*Cisco CallManager: A software that runs on a Windows 2000 server and sets up and tears down calls between phones, integrating traditional PBX functionality with IP network. Cisco CallManager manages the components of the IP telephony system—the phones, access gateways, and the resources necessary for such features as call conferencing and route planning.

(More on CallManager some other time…)

Cisco IP phone: 7940 series

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IP phone front view and buttons.
1 - Handset light strip: Indicates an incoming call or new voice message
2 - Phone screen: Shows phone features
3 - Model type: Indicates your Cisco IP phone model
4 – Programmable buttons
· Phone lines
· Speed-dial numbers
· web-based services (eg: Personal address book button)
· Phone features (eg: privacy buttons)
5 – Footstand button: Allow you to adjust the angle of the phone base
6 – Directories button: Opens/closes the Directories menu. Use it to access call logs and corporate directories.
7 – Help button: Activates the help menu.
8 – Settings button
9 – Speaker button
10 – Mute button
11 – Headset button
12 – Volume button
13 – Services button; Opens/closes the Services menu.
14 – Message button: Typically auto-dials your voice message services.
15 – Navigation button
16 – Keypad
17 – Softkey button – Each activates a softkey option displayed in the screen.

Cisco IP phone back end connectivity:

1 – DC adapter port (DC48V) for phones not provided with inline power.
2 – AC to DC power supply
3 – AC power chord
4 – Network port (10/100SW) for connecting to the network
5 – Access port (10/100 PC) for connecting your phone to your computer
6 – Handset port
7 – Headset port
8 – Footstand button

Lines v/s Calls:

Lines: Cisco IP phone supports up to two lines. The number of lines available is decided by the administrator and you can see the number of lines available on your phone screen.
Calls: Each line can support multiple calls. Therefore, you can handle several calls on the same line itself. Default number of calls is 4; it can be up to a max of 200 calls.

The features and functions of IP phones are surprisingly easy for anyone to understand. I don't think I'll have to explain it here. :)

IP Phones

An IP phone uses Voice over IP technologies allowing telephone calls to be made over the internet instead of the ordinary PSTN system. Voice over Internet Protocol is a protocol optimized for the transmission of voice through the Internet or other packet switched networks.

The most attractive part of implementing such a system is the lower calling cost. When calling other IP phones over the internet one pays for the fixed cost of internet bandwidth. Therefore IP phones are widely used in making international calls in Call centers and other business organizations.

All you need to do is to get an IP phone adapter from your VoIP service provider and that’s it. The good thing about using IP phones is that you do not need any special equipment to make it work, just the adapter. When you use IP phone systems, it works with an Ethernet port (or also called RJ-45) rather than using a regular wall phone jack. When use your IP phone service to make calls, your digital IP phone will connect through your broadband Internet modem.

Advantages of VoIP:

If you have a broadband connection with either DSL or cable, then you can use VoIP to make low cost calls. For a PC-to-PC phone call it can even be no cost to any other computer anywhere in the world (that has VoIP service installed as well, of course). Skype, Gtalk and Yahoo messenger provides this service. While there is usually a cost to make a PC-to-phone connection, it is usually less than a “traditional” long distance call.

Many VoIP service providers will charge a monthly fee allowing you to make unlimited calls within a specified geographical area, with a nominal extra charge for calls outside that set area. VoIP provides the advantage of portability if you are a traveler, you just have to sign in to your VoIP service wherever you are and make the call.

This portability is available for phone-to-phone VoIP service as well. Your VoIP service provider will provide you with an internet phone number that follows you wherever you go.

Services like call forwarding, call waiting, voicemail, caller ID, three-way calling and more are available through your IP phone, usually at no extra charge. You can also send data, as you would expect with a broadband internet connection, like pictures and documents, all while talking on the phone.

Disadvantages of VoIP:

The biggest problems of VoIP are power interruptions, quality of service and reliability.

The normal phones are not powered by your power line and thus they work when you have a power outage. These phones are powered by the phone line itself. This isn’t the case with an IP phone. If the power goes out, then there is nothing to power your internet connection or your IP phone.

There are also issues with VoIP sound quality and reliability. Just like any data sent over the internet, it is sent through the network scrambled into “packets”. Email and other documents sent over the internet are easily “reassembled” at the other end for a seamless transmission. Due to the real-time nature of voice communication, this reassembly process becomes more of a problem with VoIP. In order to minimize the delay of the voice connection, some data packets may occasionally need to be “dropped” if they don’t arrive in time, resulting in short periods of silence in the audio stream.

The amount of dropped data depends on the distance and speed of the connection. High traffic networks may experience more dropouts, especially at times of peak usage. One workaround that service providers can use is to create dedicated data paths for audio transmission.

I’ll explain about the popular 7940 series Cisco IP phone and how it is configured in another post.

Cheers ;)

The Ping Command

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I’d say the ping and traceroute commands are the simplest yet the most powerful commands in network troubleshooting. It comes very useful while isolating network hardware problems and incompatible configurations.

Ping (Packet InterNet Grouper) works by sending ICMP “echo request” packets to the target host and listening for ICMP “echo response” replies. Ping estimates the round-trip time, generally in milliseconds, and records any packet loss, and displays a summary.

ping 127.0.0.1 - This command pings the loopback address and verify the TCP/IP configuration.
ping IP_address_of_local_host - This veries that the local computer is added to the network correctly
ping IP_address_of_default_gateway - This command verify that the default gateway is functioning and that you can communicate with a local host on the local network.
ping IP_address_of_remote_host - You can ping the IP address of the remote host to verify that you can communicate through a router.

Shown below is a picture perfect scene. everything is ok in this ping reply.

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\Documents and Settings\home>ping comp1
Pinging comp1.homenet.com [10.161.133.26] with 32 bytes of data:

Reply from 10.161.133.26: bytes=32 time<1ms ttl="127">
Reply from 10.161.133.26: bytes=32 time<1ms ttl="127">
Reply from 10.161.133.26: bytes=32 time<1ms ttl="127">
Reply from 10.161.133.26: bytes=32 time<1ms ttl="127">

Ping statistics for 10.161.133.26: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms

as you can see, the packet loss is 0% which means that the communication is healthy. This may not be the case all the time, but then the ping reply can give you a lot of information regarding the network. Since it's almost 3 in the morning, I'll write about it in the next post - hopefully :)

Check out these Ping command prefixes, they are extremely useful. You will get the below mentioned list by typing the following command ping /? in the command line.

ping -t a.b.c.d - This command keeps pinging the IP address a.b.c.d until you give the break command Ctrl+C. Its useful when you have to see the effect on connectivity in realtime while doing some changes.
ping -a a.b.c.d - This command resolves IP address to host names. Put in the IP address and you will get the host name of the system.
ping -n 20 a.b.c.d - This command can be used to send 20 (or any number of) echo request to a particular IP.
Similarly there are others which are less used compared the above three.
-l size - Send buffer size.
-f - Set Don't Fragment flag in packet.
-i TTL - Time To Live.
-v TOS - Type Of Service.
-r count - Record route for count hops.
-s count - Timestamp for count hops.
-j host-list - Loose source route along host-list.
-k host-list - Strict source route along host-list.
-w timeout - Timeout in milliseconds to wait for each reply.

That's all for now. Gotta catch some sleep ;)

TACACS

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Terminal Access Controller Access-Control System (TACACS) is a remote authentication protocol that is used to communicate with an authentication server commonly used in UNIX networks.
TACACS allows a client to accept a username and password and send a query to a TACACS authentication server, sometimes called a TACACS daemon or simply TACACSD. This server is normally a program running on a host. The host would determine whether to accept or deny the request and send a response back. The TIP would then allow access or not, based upon the response. In this way, the process of making the decision is "opened up" and the algorithms and data used to make the decision are under the complete control of whoever is running the TACACS daemon.

The below diagram shows user accessing the network through the Network Access Server and then disconnecting.

• Network Access Server get username/password pair from remote user, and sends this with a 'Login' to the TACACS Server (Authentication phase).
• When the user and password combination is valid then the TACACS Server sends a 'Reply' accepted.
• The NAS sends a 'Logout' request to permit the TACACS server to go into SLIP mode.
• The TACACS server replies with a 'Reply' accepted and logs the user out.

TACACS protocol provides access control for routers, network access servers and other networked computing devices via one or more centralized servers.

A later version of TACACS introduced in 1990 was called XTACACS (extended TACACS). These two versions have generally been replaced by TACACS+ and RADIUS in newer or updated networks. TACACS+ is a completely new protocol and is therefore not compatible with TACACS or XTACACS.

TACACS is an encryption protocol and therefore less secure than the later TACACS+ and Remote Authentication Dial-In User Service protocols.

Port and Port Numbers

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A port number is a way to identify a specific process to which an Internet or other network message is to be forwarded when it arrives at a server. For TCP and UDP, a port number is a 16-bit integer that is put in the header appended to a message unit. Therefore, ports are typically used to map data to a particular process running on a computer.

Imagine IP addresses as the street address of an apartment building, and the port number as the number of a particular apartment within that building. If a letter (a data packet) is sent to the apartment building (IP) without an apartment number (port number) on it, then nobody knows who (which service) it is for. In order for the delivery to work, the sender needs to include an apartment number along with the address to ensure the letter gets to the right address.

In both TCP and UDP, each packet header will specify a source port and a destination port, each of which is a 16-bit unsigned integer (i. e. ranging from 0 to 65535), as well as specifying the source and destination network addresses (IP - numbers) among other things. A process may "bind" to a particular port to send and receive data, meaning that it will listen for incoming packets whose destination port matches that port number, and/or send outgoing packets whose source port is set to that port number. Processes may also bind to multiple ports.

As an example, a server used for sending and receiving email may provide both an SMTP (for sending) and a POP3 (for receiving) service; these will be handled by different server processes, and the port number will be used to determine which data is associated with which process. By convention, the SMTP server will listen on port 25, while POP3 will listen on port 110, although it is possible to use different ports.

Not all network transport layer use network ports; for example, although UDP and TCP use ports, ICMP does not.

The port numbers are divided into three ranges:
The Well Known Ports are those from 0 through 1023. The well-known port numbers are the port numbers that are reserved for assignment by the Internet Corporation for Assigned Names and Numbers (ICANN) for use by the application end points that communicate using the Internet's TCP or UDP.
The Registered Ports are those from 1024 through 49151. Registered port numbers are network ports in the range 1024-49151 (out of a range of 216 = 65536). They can be registered to certain protocols by software companies, similar to the way domain names are registered.
Eg: Port 28960 assigned for the game Call of Duty 2 (PC Version), Port 27010 assigned for Half-Life and its mods, such as Counter-Strike.
The Dynamic and/or Private Ports are those from 49152 through 65535. The dynamic port numbers (a.k.a private port numbers) are the port numbers that are available for use by any application to use in communicating with any other application, using the Internet's TCP or UDP.

List of TCP and UDP port numbers:

Before the arrival of ICANN, the port numbers were administered by the Internet Assigned Numbers Authority (IANA).