netwyman

Some system administrators often block   ICMP   messages to their servers in order to hide the Linux boxes to outside world on rough networks or to prevent some kind of IP flooding and denial of service attacks. The most simple method to block   ping command   on Linux systems is by adding an   iptables   rule, as shown in the below example.   Iptables   is a part of Linux kernel   netfilter   and, usually, is installed by default in most Linux environments. # iptables -A INPUT --proto icmp -j DROP # iptables -L -n -v [List Iptables Rules] Another general method of blocking ICMP messages in your Linux system is to add the below kernel variable that will drop all ping packets. # echo “1” > /proc/sys/net/ipv4/icmp_echo_ignore_all In order to make the above rule permanent, append following line to   /etc/sysctl.conf   file and, subsequently, apply the rule with   sysctl   command. # echo “net.ipv...

High availability (HA) is the ability of a system or system component to be continuously operational for a desirably long length of time. Availability can be measured relative to "100% operational" or "never failing." In information technology (IT), a widely-held but difficult-to-achieve standard of availability for a system or product is known as "five 9s" (99.999 percent) availability. Availability experts emphasize that, for any system to be highly available, the parts of a system should be well-designed and thoroughly tested before they are used. Since a computer system or a network consists of many parts in which all parts usually need to be present in order for the whole to be operational, much planning for high availability centers around backup and failover processing and data storage and access. How availability is measured availability percentage is calculated as Below: Availability = (minutes in a month - minutes of downtime) * 100/...