CentOS IPv6 Network Configuration

You need to configure following files for IPv6 configuration:

— /etc/sysconfig/network : Turn on networking in this file.
— /etc/sysconfig/network-scripts/ifcfg-eth0 : Set default IPv6 router IP and server IP address in this file.

Open /etc/sysconfig/network file:

[root@austin log]# nano /etc/sysconfig/network

Add to the following line:


Open /etc/sysconfig/network-scripts/ifcfg-eth0 (1st network config file)

[root@austin log]# nano /etc/sysconfig/network-scripts/ifcfg-eth0

# =============================================================
# Network Interface Script generated by BareMetal
# =============================================================

Save and close the file. Restart networking:

[root@austin log]# service network restart

Verify your configuration by pinging ipv6 enabled site such as ipv6.google.com:

[root@austin log]# ping6 ipv6.google.com

What is uplink port speed on a dedicated server?

What is uplink port speed on a dedicated server with 100MBPS port?

Put another way, there are 8 bits to a byte, 1024 bytes to a kilobyte and 1024 kilobytes to a megabyte. 100 Mbits = 100/8 MBytes = 12.4 MBytes/sec; 10 Mb = 1.24 MB/sec.

1Gbps uplink (would max out at around 125MB/sec).

In terms of dedicated servers, the uplink port speed is most likely the speed of the connection between the server and the router to the backbone. If the host company’s connection to the ‘net in general is faster than your uplink speed (most likely the case), then the uplink port speed will be a bottleneck.

Measure of file size: KBps
File size i.e. how big the file or how much space a file occupies in the hard disk measured in terms of KiloBytes (KB upper case “K” and upper case “B”). In computing terms the upper case “K” stands for 1024. 1024 is computed from 210. (2 power 10). 2 denote the number of characters in the binary system which is used to store data in the disc (ones and zeroes).
Other abbreviations like mega, giga and terra also use the base as 1024,

1KB (KiloByte) = 1024 Bytes (approximately 1000 Bytes)
1MB (MegaByte) = 1024 KB (approximately 1000 KiloBytes or 1 million Bytes)
1GB (GigaByte) = 1024 MB (approximately 1000 MegaBytes or 1 billion Bytes)
1TB (TerraByte) = 1024 GB (approximately 1000 GigaBytes or 1 trillion Bytes)

Measure of data transfer speeds: kbps
Data transfer speed over the networks (including the internet) is calculated in terms of bits per second: kilobits (kb small case “k” and small case “b”). The higher the kbps i.e. more the bits transferred per second, more the speed, faster the network/connection. Here k stands for 1000 (103 )

1 kbps (kilo bits per second) = 1000 bits per second
1 Mbps (mega bits per second) = 1000 kilo bits per second.
1 Gbps (giga bits per second) = 1,000 mega bits per second.

ISP bandwidth and download speeds
The most common confusion caused by the similarity of KBps and kbps is when it comes to internet bandwidth and download speeds. People often complain that their ISP promised 512kbps connectivity but they are seldom able to download any file at 512 KBps. They fail to notice the difference in cases of the units and hence think their ISP is cheating them or offering them poor quality service. As mentioned earlier data transfer speeds are always calculated in terms of kilo bits per second (kbps) so an ISP connectivity of 512 kbps promises of transfer of at the max 512 kilo bits per second.

On the other hand, file size measure is always in Kilo Bytes and thus download speeds are always calculated based on how many Bytes per second are downloaded and hence Kilo Bytes per second (KBps). KBps and kbps are not interchangeable.

So an internet connectivity of say 512kbps can never achieve a download speed of 512 KBps. To calculate the maximum download speed of a “X kbps” connection, we need to use a simple formula as below.

Download KBPS speed = (Kbps value*1000) /8)) / 1024.

I.e. For a connectivity of 512 kbps

kbps value * 1000 = 512 * 1000 = 512000

512000 / 8 = 64000

64000 / 1024 = 62.5 KBps

Therefore theoretically an internet connection of 512kbps bandwidth can download at a speed of 62.5 KBps

If you don’t want to go through all the hassles of the above formula, just multiply the kbps value with 0.1220703125 to get the KBps value.

512 kbps * 0.1220703125 = 62.5 KBps. Simple!

Internet connectivity Download speed (approx)
256 kbps 31.3 KBps
384 kbps 46.9 KBps
512 kbps 62.5 KBps
768 kbps 93.8 KBps
1 mbps ~ 1000kbps 122.1 KBps

How to Install Telnet Client on CentOS 6.3

Telnet is most likely to be used by system administrators, program developers and anyone who has a need to use specific applications or data located at a particular host computer. It’s a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. Telnet does not installed automatically on CentOS 6.3. You can issue the following command to confirm that telnet is working :

telnet localhost 80

If telnet client does not installed, it should return something like :

[root@centos63 ~]# telnet localhost 80
-bash: telnet: command not found

Issue the following command to install telnet client :

[root@centos63 ~]# yum install telnet -y
Loaded plugins: fastestmirror, presto
Determining fastest mirrors
 * base: mirrors.hostemo.com
 * extras: mirrors.hostemo.com
 * updates: mirrors.hostemo.com
CentOS6.3-Repository                                                         | 4.0 kB     00:00 ...
base                                                                         | 3.7 kB     00:00
extras                                                                       | 3.0 kB     00:00
updates                                                                      | 3.5 kB     00:00
updates/primary_db                                                           | 2.2 MB     00:19
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package telnet.i686 1:0.17-47.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

 Package           Arch            Version                    Repository                       Size
 telnet            i686            1:0.17-47.el6              CentOS6.3-Repository             56 k

Transaction Summary
Install       1 Package(s)

Total download size: 56 k
Installed size: 102 k
Downloading Packages:
Setting up and reading Presto delta metadata
Processing delta metadata
Package(s) data still to download: 56 k
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : 1:telnet-0.17-47.el6.i686                                                        1/1
  Verifying  : 1:telnet-0.17-47.el6.i686                                                        1/1

  telnet.i686 1:0.17-47.el6


If telnet client installed, it should return something like :

[root@centos63 ~]# telnet localhost 80
Trying ::1...
Connected to localhost.
Escape character is '^]'.