Subnetmask in HEX

Overview of common subnets and masks Mask Hosts  Usable Netmask          Hex Mask /30  4      2      255.255.255.252  fffffffc  this is 1/64 of a Class C net /29  8      6      255.255.255.248  fffffff8  this is 1/32 of a Class C net /28  16     14     255.255.255.240  fffffff0  this is 1/16 of a Class C net /27  32     30     255.255.255.224  ffffffe0  this is 1/8 of a Class C net /26  64     62     255.255.255.192  ffffffc0  this is 1/4 of a Class C net /24  256    254    255.255.255.0    ffffff00  this is a Class C net /23  512    510    255.255.254.0    fffffe00  these are 2 Class C net /22  1024   1022   255.255.252.0    fffffc00  these are 4 Class C net /21  2048   2046   255.255.248.0    fffff800  these are 8 Class C net /20  4096   4094   255.255.240.0    fffff000  these are 16 Class C net /19  8192   8190   255.255.224.0    ffffe000  these are 32 Class C net /18  16384  16382  255.255.192.0    ffffc000  these are 64 Class C net /17  32768  32766  255.255.128.0    ffff8000  these are 128 Class C net /16  65536  65534  255.255.0.0      ffff0000  these are 256 Class C net = Class B net

md5sum csum fciv

LINUX: md5sum fileName

In Linux, the md5sum utility can be used:
aemtux1:/ % md5sum binary.file
0c4627e70d168f7f78257e6dd01fdb60 binary.file

This utility is provided by the following rpm package (the package name is the key element, because the version number depends on your Linux installation)
% rpm -qf /usr/bin/md5sum
coreutils-5.2.1-23.13


AIX: csum -h MD5 fileName

In AIX, there is no native "md5sum" but the MD5 hash function is provided by csum (provided and supported in AIX 5.3 and later):
csum -h MD5

aemaix1:/ % csum -h MD5 binary.file
0c4627e70d168f7f78257e6dd01fdb60 binary.file

Note: You may need to apply fixes to AIX for csum to handle files larger than 2 GB. For example:
IV03170: csum to support files more than 2GB APPLIES TO AIX 6100-07


Solaris: digest -a md5 -v fileName

In Solaris there is no native "md5sum", but "digest" can be used:

aemsun4:/ % digest -a md5 -v binary.file
md5 (binary.file) = 0c4627e70d168f7f78257e6dd01fdb60


HP-UX: md5sum fileName

HP-UX MD5 Secure Checksum 
Product details & specifications 
Overview 
The HP-UX MD5 Secure Checksum A.01.01.02 bundle (bundle name MD5Checksum) provides a file integrity utility and API based on the standard Message Digest 5 (MD5) algorithm. The MD5Checksum bundle consists of the following two components that can be installed independently: 
- HP-UX MD5sum (md5sum checksum command) 
- HP-UX LibCryptX (libcryptx libraries providing MD5 APIs) 
The md5sum command is based on the MD5 algorithm and generates 128-bit message digests. The md5sum command enables you to verify the integrity of files downloaded over a network connection. You can also use the md5sum command to compare files and verify the integrity of files. 


HP NonStop Server (NSS): md5sum fileName

In HP NonStop Server, the md5sum command is available in OSS.


Windows: md5sum fileName 
fciv -md5 fileName

Microsoft does not offer a supported tool for generating the MD5 hash.

There are 2 choices:

a) The md5sum utility can be found within the following package of useful utilities that were developed to mimic their corresponding peer in Unix. The UnxUtils.zip and UnxUpdates.zip packages contain such utilities. For details on the utilities that are provided in these packages and download links see:

GNU utilities for Win32

Example run:
H:\> md5sum binary.file
0c4627e70d168f7f78257e6dd01fdb60 *binary.file

b) Microsoft offers a NON-supported utility called "fciv":

Availability and description of the File Checksum Integrity Verifier utility
The File Checksum Integrity Verifier (FCIV) is a command-prompt utility that computes and verifies cryptographic hash values of files. FCIV can compute MD5 or SHA-1 cryptographic hash values. These values can be displayed on the screen or saved in an XML file database for later use and verification.

Example run:
H:\62570,379,000\2011-01-21> fciv -md5 binary.file
//
// File Checksum Integrity Verifier version 2.05.
//
0c4627e70d168f7f78257e6dd01fdb60 binary.file

Caveat:
During the writing of this technote, we found that the fciv utility worked fine in some Windows systems but failed in other systems with the following error. We could not find a way to overcome it. Thus, use this unsupported tool at your own risk.
Error during CryptAcquireContext.
Error msg : An internal error occurred.

windows 2008 set NTP server

How to set my Windows 2008 server to use external NTP server?
In cmd:

C: \> net stop w32time
C: \> w32tm /config /syncfromflags:manual /manualpeerlist:"0.pool.ntp.org, 1.pool.ntp.org"
C: \> w32tm /config /reliable:yes /update
C: \> net start w32time
C: \> w32tm /query /configuration