Sysctl Tweaks

Edit /etc/sysctl.conf

# vi /etc/sysctl.conf

Add the following items at the bottom.

# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0
# Controls whether core dumps will append the PID to the core filename, usef$
kernel.core_uses_pid = 1

# Controls IP packet forwarding
net.ipv4.ip_forward = 1
# Controls source route verification
net.ipv4.conf.default.rp_filter = 1
# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0

net.ipv4.conf.all.src_valid_mark=1
# Controls of how network trust neighbours (not!)
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.all.send_redirects = 0

# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1
# Controls of syn backlog
net.ipv4.tcp_max_syn_backlog = 4096

# Default ipv4 settings for usage on load balanced hosts.
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
net.ipv4.tcp_mem = 786432 1048576 1572864
net.ipv4.tcp_tw_recycle = 1

# Default ipv4 connection tracking tweaks
net.netfilter.nf_conntrack_tcp_timeout_syn_recv = 30
net.netfilter.nf_conntrack_tcp_timeout_time_wait = 60
net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 30
net.netfilter.nf_conntrack_tcp_timeout_close_wait = 30
net.netfilter.nf_conntrack_tcp_timeout_established = 600
net.netfilter.nf_conntrack_max = 1048576

# Disable ipv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

# Disable ipv6 router advertisement addresses
net.ipv6.conf.all.accept_ra = 0
net.ipv6.conf.ens192.accept_ra = 0
net.ipv6.conf.default.accept_ra = 0

# Disable ipv6 autoconfiguration
net.ipv6.conf.all.autoconf = 0
net.ipv6.conf.ens192.autoconf = 0
net.ipv6.conf.default.autoconf = 0

kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128

# TCP Performance tweaks
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_syncookies = 1
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.wmem_max = 4194304


### IMPROVE SYSTEM MEMORY MANAGEMENT ###

# Increase size of file handles and inode cache
fs.file-max = 2097152

# Do less swapping
vm.swappiness = 10
vm.dirty_ratio = 60
vm.dirty_background_ratio = 2

### GENERAL NETWORK SECURITY OPTIONS ###

# Number of times SYNACKs for passive TCP connection.
net.ipv4.tcp_synack_retries = 2

# Allowed local port range
net.ipv4.ip_local_port_range = 2000 65535

# Protect Against TCP Time-Wait
net.ipv4.tcp_rfc1337 = 1

# Decrease the time default value for tcp_fin_timeout connection
net.ipv4.tcp_fin_timeout = 15

# Decrease the time default value for connections to keep alive
net.ipv4.tcp_keepalive_time = 300
net.ipv4.tcp_keepalive_probes = 5
net.ipv4.tcp_keepalive_intvl = 15

### TUNING NETWORK PERFORMANCE ###

# Default Socket Receive Buffer
net.core.rmem_default = 31457280

# Maximum Socket Receive Buffer
net.core.rmem_max = 12582912

# Default Socket Send Buffer
net.core.wmem_default = 31457280

# Maximum Socket Send Buffer
net.core.wmem_max = 12582912

# Increase number of incoming connections
net.core.somaxconn = 4096

# Increase number of incoming connections backlog
net.core.netdev_max_backlog = 65536

# Increase the maximum amount of option memory buffers
net.core.optmem_max = 25165824

# Increase the maximum total buffer-space allocatable
# This is measured in units of pages (4096 bytes)
net.ipv4.tcp_mem = 65536 131072 262144
net.ipv4.udp_mem = 65536 131072 262144

# Increase the read-buffer space allocatable
net.ipv4.tcp_rmem = 8192 87380 16777216
net.ipv4.udp_rmem_min = 16384

# Increase the write-buffer-space allocatable
net.ipv4.tcp_wmem = 8192 65536 16777216
net.ipv4.udp_wmem_min = 16384

# Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks
net.ipv4.tcp_max_tw_buckets = 1440000
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_low_latency = 1