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Networking

OpenBSD: Reload / Restart / Stop dhcpd Server Command

I manage MS-Windows server and recently started to play with OpenBSD server. How do I reload or restart the dhcpd server on OpenBSD using shell command line option?
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CentOS / RHEL: Install iftop To Display Bandwidth Usage Per interface By Host

I am running Red Hat Enterprise Linux on IBM based system. How do I display bandwidth usage on an interface by host in real time using command line option? How do I monitor bandwidth usage in a real time on RHEL or CentOS Linux based server? How can I install iftop utility on CentOS or RHEL server using the yum command?
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CentOS Linux: Add Static Routing

I am a new CentOS Linux sysadmin. How can I add static route On CentOS Enterprise Linux server running on HP amd64 server?
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Linux: Find Out What Is Using TCP Port 80

How do I find out what is listing or using tcp port number 80 on Linux based systems using command line options?
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Mac OS X: Wake Up Servers Using Wake-on-LAN ( WOL ) Command Utility

I know how to send WOL command using Linux or FreeBSD wake command. But, how do I send Wake on LAN (WOL) frames to hosts on a local Ethernet network using Apple OS X Unix operating systems to wake up my servers or nas devices?
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Ubuntu Linux: Install Wake On Lan Client For Server

How do I install wake on lan client under Ubuntu Linux desktop to wakeup Unix or Linux based servers?
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Linux: Turn On TCP SYN Cookie Protection

I am under DoS attack. My cloud based server hosting company asked me to enable TCP SYN cookie protection to save my domain from SYN Attack. How do I turn on TCP Syn cookie protection under Ubuntu or CentOS Linux based server?
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Linux: Force Close A Socket / Port On Server In a TIME_WAIT State

I run a BT client and few other server program on Linux. Sometime these programs get overloaded with too many connections and crashes. If I restart my apps, I see lots of old IPs in a TIME_WAIT state. How do I force and and close everything in a TIME_WAIT state under Linux operating systems?
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Linux: See Bandwidth Usage Per Process With Nethogs Tool

I have Red Hat Enterprise Linux 6.x server. How do I find out and groups network bandwidth usage by process under Linux operating systems? How do I find out what programs are using network bandwidth under Linux operating systems? How can I see bandwidth usage per PID, command, and user on a Linux operating systems?
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OpenBSD: Configure Network Interface As A Bridge / Network Switch

I have Soekris single board communication embedded computers which is optimized for low power and network usage. The server has four Ethernet ports. How do I setup IPv4 software bridge using OpenBSD operating systems so that the rest of four ports act as a network switch?
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