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ios
#define ios: \
I---------------------------------------------------\
I---------------------------------------------------\
I---------------------------------------------------\
I            /$$$$$$  /$$$$$$   /$$$$$$             \
I           |_  $$_/ /$$__  $$ /$$__  $$            \
I             | $$  | $$  \ $$| $$  \__/            \
I             | $$  | $$  | $$|  $$$$$$             \
I             | $$  | $$  | $$ \____  $$            \
I             | $$  | $$  | $$ /$$  \ $$            \
I            /$$$$$$|  $$$$$$/|  $$$$$$/            \
I           |______/ \______/  \______/             \
I---------------------------------------------------\
I---------------------------------------------------\
I---------------------------------------------------I

    • "Internetwork Operating System"
    • operating system for CISCO routers
    • its terribly executed, its insane these guys managed to stay in business
      considering how much thought went into their software
    • not allowing CIDR notation was a great mistake; have fun typing 255 and 0 left and right

    CONFIGURATION_DIALOG:
        • shown the first time the router is booted
        • bad
        • skip it; whatever you want, it will be faster without it

    COMMENTS:
        ! <...>
        • must be at the beginning of the line (white space is ignored)
        • cannot stand after a command

    MODES:
        • child modes are NOT supersets of their parents
        .
        ├── User EXEC mode ("enter")    // '>'
        │   │
        │ (pass)  
        │   └── Privileged EXEC mode ("enable") // '#'
        │       └── Global configuration mode ("configure terminal")
        │           ├── Interface configuration mode ("interface <interface-name>")
        │           ├── DHCP configuration mode ("ip dhcp <dhcp-subcommand>")
        │           ├── Line configuration mode ("line <line-type> <line-number>")
        │           ├── Router configuration mode ("router <routing-protocol>")
        │           ├── VLAN configuration mode ("vlan <vlan-id>")
        │           ├── Security mode ("security")
        │           ├── NTP configuration mode ("ntp <ntp-subcommand>")
        │           └── Policy-map configuration mode ("policy-map <policy-map-name>")
        ├── ROM monitor mode ("rommon")
        └── Setup mode ("setup")

    GLOBALS:
        exit
        end

    HELP:
        ?
        • the question mark can be used in any context to list all possible valid inputs
          (sometimes regex clustered)

    SHORT_CUTS:
        • UNIX style
        [ctrl] + [a]    : beginning of the line
        [ctrl] + [e]    : end of the line
        [ctrl] + [b]    : back 1 char
        [ctrl] + [f]    : forward 1 char
        [ctrl] + [d]    : delete (as in the key)
        [ctrl] + [n]    : delete line
        [ctrl] + [k]    : delete from cursor until the end of the line

    SECRET:
        • the secret is a password separating Privileged EXEC mode from User EXEC mode
        (config) enable secret

    STATE:
        • config operations are done in memory
        • on each boot the "startup-config" is read
        # save run start    : save the current configuration (in memory) to startup-config (to disk)

    DHCP_CONFIGURATION_MODE:
        (config) ip dhcp pool <pool-name>
        • IOS itself will select you which interface the pool belongs to by pattern matching
        • unless you hack/dork better than me, you cant use 1 pool for multiple interfaces
        Pool:
            (dhcp-config)# network <ip-start> <subnet-mask>     : specify from which address to start assigning from and
                                                                   how many host are there (indirectly through the subnet mask),
                                                                   thereby defining the boundaries of the pool
            (dhcp-config)# default-router <ip>                  : specify default gateway for clients of the pool
        

    STATIC_ROUTING:
        (config) ip route <destination> <mask> <forward_to>

    RIP:
        (config) router rip
        (config-router) network <network>       : enable advertising <network> over RIP; if an interface
                                                   is not specified, it will not be routed using RIP;
                                                   (ie. please specify serial and ethernet too)

    ?!:
        # show <noun>
            interfaces
            ip dhcp pool
        (config-if)# no shutdown
        (config-if)# ip <?!>
                            address <ip> <subnet-mask>      : assign ip to the routers interface;  it does no magic over the network
                            dhcp pool <pool-name>