4. IP CIDR calculator

IP CIDR calculator


  • IP Multicast address ranges

    All multicast addresses can easily be recognized because they start with the bit pattern “1110”.

    224.0.0.0 - 224.0.0.255 Well-known multicast addresses, control channels

    224.0.1.0 - 238.255.255.255 Globally-scoped (Internet-wide) multicast addresses

    239.0.0.0 - 239.255.255.255 Local multicast addresses

    Special and private address ranges

    Private address ranges are not routed on the Internet and can be freely allocated in any private network. NAT (network address translation) is required when connecting such a network to the Internet.

    Private network addresses (RFC1597/RFC1918 addresses):

    10.0.0.0 - 10.255.255.255 A 24-bit block, /8, class A network

    172.16.0.0 - 172.31.255.255 A 20-bit block, /12, set of 16 contiguous class B network numbers

    192.168.0.0 - 192.168.255.255 A 16-bit block, /16, set of 255 contiguous class C network numbers

    Special addresses:

    127.0.0.0 - 127.255.255.255 Special address range for the localhost. You can normally not use those addresses for anything else. 127.0.0.1 is generally assigned to the loopback device

    0.0.0.0 _Special host address commonly reserved for the default route _

    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
    0
 


Tmux Commands

screen and tmux

A comparison of the features (or more-so just a table of notes for accessing some of those features) for GNU screen and BSD-licensed tmux.

The formatting here is simple enough to understand (I would hope). ^ means ctrl+, so ^x is ctrl+x. M- means meta (generally left-alt or escape)+, so M-x is left-alt+x

It should be noted that this is no where near a full feature-set of either group. This - being a cheat-sheet - is just to point out the most very basic features to get you on the road.

Trust the developers and manpage writers more than me. This document is originally from 2009 when tmux was still new - since then both of these programs have had many updates and features added (not all of which have been dutifully noted here).
Action tmux screen
start a new session tmux OR
tmux new OR
tmux new-session 		screen
re-attach a detached session tmux attach OR
tmux attach-session 		screen-r
re-attach an attached session (detaching it from elsewhere) tmux attach -d OR
tmux attach-session -d 		screen -dr
re-attach an attached session (keeping it attached elsewhere) tmux attach OR
tmux attach-session 		screen -x
detach from currently attached session ^b d OR
^b :detach 		^a ^d OR
^a :detach
rename-window to newname ^b , <newname> OR
^b :rename-window <newn> 		^a A <newname>
list windows ^b w ^a w
list windows in chooseable menu ^a "
go to window # ^b # ^a #
go to last-active window ^b l ^a ^a
go to next window ^b n ^a n
go to previous window ^b p ^a p
see keybindings ^b ? ^a ?
list sessions ^b s OR
tmux ls OR
tmux list-sessions 		screen -ls
toggle visual bell ^a ^g
create another window ^b c ^a c
exit current shell/window ^d ^d
split window/pane horizontally ^b " ^a S
split window/pane vertically ^b % ^a |
switch to other pane ^b o ^a <tab>
kill the current pane ^b x OR (logout/^D)
collapse the current pane/split (but leave processes running) ^a X
cycle location of panes ^b ^o
swap current pane with previous ^b {
swap current pane with next ^b }
show time ^b t
show numeric values of panes ^b q
toggle zoom-state of current pane (maximize/return current pane) ^b z
break the current pane out of its window (to form new window) ^b !
re-arrange current panels within same window (different layouts) ^b [space]
Kill the current window (and all panes within) ^b killw [target-window]

  • sort -g /var/log/nginx/access.log | awk '{print $1}' | uniq

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  • Make ISO from DVD

    In this case I had an OS install disk which was required to be on a virtual node with no optical drive, so I needed to transfer an image to the server to create a VM

    Find out which device the DVD is:

    lsblk

    Output:

    NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 465.8G 0 disk ├─sda1 8:1 0 1G 0 part /boot └─sda2 8:2 0 464.8G 0 part ├─centos-root 253:0 0 50G 0 lvm / ├─centos-swap 253:1 0 11.8G 0 lvm [SWAP] └─centos-home 253:2 0 403G 0 lvm /home sdb 8:16 1 14.5G 0 disk /mnt sr0 11:0 1 4.1G 0 rom /run/media/rick/CCSA_X64FRE_EN-US_DV5

    Therefore /dev/sr0 is the location , or disk to be made into an ISO

    I prefer simplicity, and sometimes deal with the fallout after the fact, however Ive repeated this countless times with success.

    dd if=/dev/sr0 of=win10.iso

    Where if=Input file and of=output file

    I chill out and do something else while the image is being copied/created, and the final output:

    8555456+0 records in 8555456+0 records out 4380393472 bytes (4.4 GB) copied, 331.937 s, 13.2 MB/s

    Fin!

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