Basics of SWITCH

BASIC OF A SWITCH

A switch or network switch or called as LAN switch is a device that connects network devices as like hubs, Its more than a HUB. Its also referred as multi-port  network bridge.

• Switches operate at data link or network layer of OSI layer.
• It connects different type of network like ethernet ,fiber.
• A layer-2 switch provides hardware based bridging and uses application specific integrated circuits  ( ASICs).
• It is used to breakup the collision Domain.

• Switches create separate collision domain but a single broadcast domain.
• Main purpose of using a switch is to optimize the LAN performance and providing better bandwidth to LAN users. They only switch frame packets from one port to another.
• Switches provide dedicated collision domain and also independent bandwidth on each port.
• It comes with many Ports like hub, 12,24,28,  etc.
• Different vendors have different switches for wired and wireless LAN like Cisco, D-Link, Juniper ,Huawei, Aruba.
• Same as routers there also series of switches in cisco and other vendors.

In networking the switch is represented as symbol like :-

 

There are basic three switch Functions at layer-2 and are :

1.Address Learning

2.Forward/filter decisions

3.Loop avoidance

More information can be referred at section Basics of Switching under this Blog.

RPS

RPS a product from Cisco is Redundant Power System. It provides power supply redundancy and resiliency for switches and routers power requirement through POE (Power over Ethernet) mode.

Basically the RPS was used for catalyst models such as 3750-E, 3560-E. It avoids network downtime by preventing switch reboot after a internal switch failure. It is ease of use and ease of deployment. 

Virtual Switch:

Now a days there are virtual switches introduced in the market. A virtual switch works with virtual NIC. The virtual NIC is is software linked with unique MAC address that can be later used by a virtual machine to send and receive packets. 

-DR

Basics of HUB

Network HUB 

A HUB is a device, used in a LAN environment or used for connecting more than one computer. It has many number of PORTS for connection via UTP (RJ 45)cable. It is a small rectangular plastic box type having 4-5 PORTS. Similarly Large HUBS ranges from 8,12, 24 PORTS.

• When a message (DATA) is passed from one computer to the HUB, then the HUB broadcasts the message to all of its PORTS means all other computers can access in the same time. Which may occur Collision in the DATA access, transfer .
• One Advantage of using HUB is its very less expensive compared to switches.
• The Disadvantage is ,the ports lie in single collision domain. The message or data comes to the HUB repeats many time at ports. Its non secure as DATA can be tracked or hacked.

   

HUBs are physical layer ( L1 ) devices and may be called as multiport repeater. Due to the broadcast feature, the packet frame is passed through all ports. 

Its basically useful for Home use or smaller networks as they are unmanaged.

-DR

Basic Network troubleshooting

Basic Network troubleshooting

Ping:

Ping is a command-line utility and is used for network troubleshooting.  It is available with every operating system by default. You need to open command prompt (cmd). 

After opening cmd, just type ping followed by host address (IP address) where you want to reach out. It is mostly required to know whether communication with the host is possible or not.  It works like, it sends out an ICMP echo request and receives a reply.

You can send ping request to web addresses too. For example, you can send ping request to google.com just by the below syntax,

C:\>ping www.google.com

C:\>Ping 127.0.0.1

If there is any missing reply, then it is understood that, there is some issue with the connectivity.

The time mentioned is between 13 milliseconds (ms) to maximum 50ms or more. It comes with approximate round trip times. 

When we are working in a LAN environment and we face there is any internet issue arises, we need to ping first to the gateway (or router) through which it connects internet. Some even ping to global DNS server of Google i.e. 8.8.8.8

Sometimes, administrators ping to switch, firewall and even computers from their own computer to check the connectivity is fine.

Sometimes a continuous ping is required while the troubleshooting work such as wire adjustments, punching repair is ongoing. In that case additional (-t) can be just added to the ping command such as 

C:\>ping 127.0.0.1 –t

Loopback plug

loopback plug or loopback adapter, which is a plug used to test physical ports to identify network issue. It can identify issues in network, network interface card, router interface etc.

Similarly it can be used in serial port, parallel USB ports, OFC ports etc.

IPconfig:

Ipconfig is a command line utility used with command (cmd) window. It is used to display all the details about the network. It shows the host IP address, router or adaptor IP address, VPN client address, subnet mask used, default gateway address etc. 

If you need to see all other information such as Physical MAC address, DNS and DHCP servers address, DHCP enable status then you need to use /all parameter with the syntax.

If you need help then you need to add question mark symbol 

Example

C:\Users\ User name >ipconfig 

C:\users\username>ipconfig/all

C:\Users\Username>ipconfig/?

Other than ipconfig syntax, you can know only MAC addresses by typing getmac at the command prompt. And use systeminfo to know many information about the system.

NSlookup:

NSlookup or Name server lookup command is used to diagnose or troubleshoot Domain Name System (DNS) and host name resolution. It is available if you are using TCP/IP protocol. It comes with two modes i.e. interactive and non-interactive.

In interactive mode, you can get only single set of data or information.

Example

C:\User\Username>nslookup www.google.com

You will receive all the name server address, IPv4 address of google.com

In non interactive mode you will receive more than one information at a time. 

By using the name server or DNS server, it translates the domain name to an IP address.

Netstat:

Netstat is a network administrator’s command and it displays TCP connections, ports on which a host is listening, IP routing table, IPV4 parameters etc.

Syntax is such as

Netstat -a: It shows all active TCP connections on which host is listening.

Netstat –e: It shows all the Ethernet statistics that includes number of bytes and packets sent and received, any errors if present, unicast packets, unknown protocols etc.

Netstat-r: It shows the contents of IP routing table.

PuTTY:

PuttY is an SSH and telnet client, developed by Simon Tatham for the windows platform. It is an open source software that is available with source code and with both 64 bit and 32 bit. You can download and use it for several activity such as Telnet, configuring devices, SCP, SSH. It provides a command line interface.

Speedtest.net:

Speedtest dot net is a very interactive tool to test the speed and performance of your internet connection. They have thousands of servers across globe that hosts the speedtest server.

-DR