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Showing posts from September, 2014

Network Address Translation (NAT) for IPv4 ~ Made easy

There are mainly three methods available

Static NAT
Dynamic NAT
PAT (Port Address Translation or NAT-Overloaded)

Static NAT - one to one ip mapping

Static NAT uses a one-to-one mapping of local and global addresses. These mappings are configured by the network administrator and remain constant.



Dynamic NAT- many to many ip mapping

Dynamic NAT uses a pool of public addresses and assigns them on a first-come, first-served basis. When an inside device requests access to an outside network, dynamic NAT assigns an available public IPv4 address from the pool.



Port Address Translation (PAT) - many(x) to many(y) ip mapping .. (x>y)

PAT (also called NAT overload) conserves addresses in the inside global address pool by allowing the router to use one inside global address for many inside local addresses. In other words, a single public IPv4 address can be used for hundreds, even thousands of internal private IPv4 addresses.

Many-to-one address mapping between local and global addresses. This method i…

Can't upgrade ubuntu due to low disk space on /boot (Linux)

If you get some error like this while updating Ubuntu (Linux)

The upgrade has aborted. The upgrade needs a total of 56.7 M free space on disk '/boot'. Please free at least an additional 3,816 k of disk space on '/boot'. Empty your trash and remove temporary packages of former installations using 'sudo apt-get clean'.

Reason:

Your file system doesn't have enough free space to install new packages of newer version to /boot partition

Solution is:

1>Run following command on terminal

dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d'

>>results will be like this
linux-headers-3.11.0-20
linux-headers-3.11.0-20-generic
linux-headers-3.11.0-22
linux-headers-3.11.0-22-generic
linux-headers-3.11.0-23
linux-headers-3.11.0-23-generic
linux-headers-3.11.0-24
linux-headers-3.11.0-24-generic
linux-image-3.11.0-20-generic
linux-image-3.11.0-22-generic
linux-image-…