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Latest Articles
Xcopy
February 21, 2020
Xcopy is a powerful and fast copy tool: most common switches: /E option causes to copy empty sub directories to the destination folder. /H option the the command would also copy hidden and system files to the destination folder. /I It would not copy files from sub directories. Adding /I switch will avoid the question to...
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MDNS causing campus global network outage
February 21, 2020
SYMPTOM Network size: 1800 students, 200 faculties. All network (LAN connection or internet) stopped functioning for about 30 seconds every 4 hours in the beginning(Spanning tree issue) then mostly in the morning when people start to work, then recover itself. Find the ownership Due to the school network was a flat design, all the devices...
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Troubleshooting – Network
February 21, 2020
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Cisco PPTP VPN
February 14, 2020
R1(config)# conf t R1(config)# username aaron secret MyPassword Now we need to activate aaa new model to expose new commands: R1(config)# aaa new-model Set up ppp authentication for local database by default: R1(config)# aaa authentication ppp default local We must provide authorization for the client computer, in this case we’ll do this automatically if the...
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Create a portable hard drive boot image
February 13, 2020
Step 1: Format the Drive Just place the flash drive in the USB port of your computer. Open command prompt (cmd). You can do that by pressing WINKEY+R, right click on the listed file and click on “Run as administrator“. Enter the following commands in the same order as I did here: diskpart list disk...
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Install php from Source Code
February 12, 2020
Install Requirments yum install bzip2-devel curl-devel libjpeg-devel libpng-devel freetype-devel libxml2-devel libc-client-devel libmcrypt-devel -y Download Package You can find the version address here https://www.php.net/downloads cd /tmp wget -O php-5.6.22.tar.gz http://pl1.php.net/get/php-5.6.22.tar.gz/from/this/mirror tar -zxvf php-5.6.22.tar.gz cd php-5.6.22 Compile php ./configure --enable-bcmath --with-bz2 --enable-calendar --with-curl --enable-exif --enable-ftp --with-gd --with-jpeg-dir --with-png-dir --with-freetype-dir --enable-gd-native-ttf --with-kerberos --enable-mbstring --with-mcrypt --with-mhash --with-mysql --with-mysqli --with-openssl...
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UDLD Unidirectional Link Detection
February 4, 2020
UDLD (unidirectional link detection) is a supplementary protocol to Spanning tree protocol at Data link layer, before introducing UDLD, let’s have a review on STP. Spanning-Tree Protocol (STP) resolves redundant physical topology into a loop-free, tree-like forwarding topology. This is done by blocking one or more ports. By blocking one or more ports, there are...
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Configure DHCP server on a MAC
January 30, 2020
This guide is intended to show you how to provide an IP address to an Atlona unit whose NIC (network interface card) is set to accept IP addresses automatically using a DHCP server. Before you begin this guide, please connect your computer to the Atlona product’s LAN port with a CAT5e or better Ethernet patch...
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Wireless machine authentication issue EventID 6273 ReasonCode 265
January 30, 2020
One of the laptop could not log on the campus WIFI with machine account. Found the log in Event viewer on NPS server: Network Policy Server denied access to a user.Network Policy Server denied access to a user. Contact the Network Policy Server administrator for more information. User: Security ID: DOMAIN\2017-P446-SARS$ Account Name: host/2017-P446-SARS.xxx.xxx...
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Hardware
January 24, 2020
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Configure Cisco unified border element (CUBE) gateway 2
November 28, 2019
Configure CUBE Protocol Interworking Command To enable protocol interworking, use the allow-connections from-type to to-type command in voice service configuration mode. The from-type and to-type options specify the signaling protocols, as detailed in Table 9-2. Table 9-2 allow-connections Syntax Description Parameter Description from-type Originating endpoint type. The following choices are valid: h323—H.323 sip—SIP To...
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IPBAN – Windows
November 26, 2019
In Linux we can use fail2ban to prevent brute attack based on the login failure attempt. Windows has a similar tool called IPBAN. The tool can be downloaded from github. Requirement Check your windows version, only windows 8.1 or newer, windows server 2012 or newer. Windows Server 2008 does a poor job of logging ip...
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Voice Signalling protocols 1 – SIP
November 21, 2019
Voice Signaling protocol: SIP Session Initiation Protocol (SIP) is one of the most important voice signaling protocols within service provider VoIP networks and is supported by most IP telephony system vendors. As such, it is an ideal protocol for interconnecting different VoIP systems and networks. SIP operates on the principle of session invitations that are...
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Configure basic VoIP 1 (stages of VoIP, RTP, VAD)
November 20, 2019
Major Stages of Voice Processing in VoIP For voice transmission over an IP network, the voice wavelength must be sampled, quantized, encoded, optionally compressed, and then encapsulated in a VoIP packet. The first four steps are performed by a digital signal processor (DSP) in the originating gateway and are detailed in the following section....
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VoIP Essential 2 (Codecs, DSPs )
November 18, 2019
Codecs A codec is a device or program capable of performing encoding and decoding on a digital data stream or signal, which works on presentation layer in VoIP. Various types of codecs are used to encode and decode or compress and decompress data that would otherwise use large amounts of bandwidth on WAN links....
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Prevent DDoS on Network Devices
November 13, 2019
Rate Limiting With some types of DoS attacks, there’s not much you can do to stop the flow of the attack, especially in a distributed DoS (DDos) attack in which the hacker is spoofing the source addresses and using an unsuspecting company or ISP as the reflector in the attack. Tracing this kind of...
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Cisco AP Discovery and Join WLAN controller
November 7, 2019
Access point (AP) registration consists of a discovery and join process. Registration is the first step in getting your wireless network up and running. If you understand how the discovery and join process works, your job will be much easier when you have to troubleshoot it. One of the major selling points of the AP and...
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Cisco WLAN AP placement
November 7, 2019
The APs would be connected to your access layer switches in a management or other isolated VLAN to keep the APs from having to process unnecessary packets. Another consideration is how to deploy the APs per controller on the network if you will have more than one. A common deployment is known as a salt-and-pepper or...
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MAC reference machine build and imaging (10.14 Mojave)
November 1, 2019
Dock standardrize Login as a local admin, build a reference dock. Open Terminal type sudo -s Enter your current account’s password when prompted Copy the modified dock preference file to the User Template in your Mac’s System folder:cp ~/Library/Preferences/com.apple.dock.plist /System/Library/User\ Template/en_AU.lproj/Library/Preferences/Note the en_AU is your system lanuguage preference, you can find it in the system...
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Apple Profile manager pending
October 29, 2019
The Profile manager does not push APP/Settings to Enrolled Devices Network requirement: To use Profile Manager, you should make sure that the following ports are open on your network. Port Incoming or Outgoing TCP/UDP Description 2195, 2196 Outgoing TCP Used by Profile Manager to send push notifications 5223 Outgoing TCP Used to maintain a...
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MAC usuful commands
October 29, 2019
switch on/off wifi: networksetup -setairportpower en1 off login script: sudo defaults write com.apple.loginwindow LoginHook /path/to/script To Check it sudo defaults read com.apple.loginwindow To remove this hook, delete the property: sudo defaults delete com.apple.loginwindow LoginHook Troubleshoot: use grep LogoutScript /var/log/system.log Untick the “Auto Proxy Discovery” Networksetup -setproxyautodiscovery Ethernet off Clean up messy open with...
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fail2ban configure with Apache, SSH,
October 25, 2019
OS: CentOS 7 Configure fail2ban Configure Fail2ban Fail2ban reads .conf configuration files first, then .local files override any settings. Because of this, all changes to the configuration are generally done in .local files, leaving the .conf files untouched. Configure fail2ban.local fail2ban.conf contains the default configuration profile. The default settings will give you a reasonable working setup. If you want to make any changes,...
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Windows server install error 0x80070570
October 22, 2019
Recently Bought a new Server with below specs: Dell R740 32GB RDIMM, 2933MT/s X 8 Intel Xeon Silver 4210 2.2G, 1 0C/20T, 9.6GT/s, 13.75M Cache, Turbo, HT (85W) DDR4-2400 NVIDIA Tesla P40 24GB GPU, Pas sive Dell 6.4TB, NVMe, Mixed Use Ex press Flash, HHHL AIC, PM1725b x 2 build with Dell onboard S140 RAID...
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Asterisk – Basic (Extension, SIP phone, Voicemail)
October 17, 2019
There are multiple types of extension in Asterisk, which are using different ports to register. The most popular one is PJSIP (UDP5060) which is default by most of the sip phones, on iPhone, the Softphone, Xlite. The option you need to configure are: Extension number: which is used as the UserName Secret: which is used...
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