As you work with IOS, you’ll become intimately familiar with
the show
commands. They are among
the most useful commands you will ever use; they allow you to view
just about any settings within the router. Issuing the command
show
?
produces output like
this:
Router>show ?
clock Display the system clock
history Display the session command history
hosts IP domain-name, lookup style, nameservers, and host table
sessions Information about Telnet connections
snmp snmp statistics
terminal Display terminal configuration parameters
users Display information about terminal lines
version System hardware and software status
The
show
command has many different subcommands.
However, notice that we are in user mode. In privileged mode, the
show
command has a lot more subcommands, which
would take up a few pages if we listed them here. The important thing
to remember is that show
commands often have more
than one keyword. For example, the command
show ip route
works by itself, but there are also
many other options that can be applied to it. For example:
router#show ip route ?
Hostname or A.B.C.D Network to display information about or hostname
bgp Border Gateway Protocol (BGP)
connected Connected
egp Exterior Gateway Protocol (EGP)
eigrp Enhanced Interior Gateway Routing Protocol (EIGRP)
igrp Interior Gateway Routing Protocol (IGRP)
isis ISO IS-IS
odr On Demand stub Routes
ospf Open Shortest Path First (OSPF)
rip Routing Information Protocol (RIP)
static Static routes
summary Summary of all routes
supernets-only Show supernet entries only
<cr>
I certainly haven’t explained routing enough for you to
understand the output of this command. However, you can see how to
find show
keywords with the question mark. The
<cr>
shown in the previous example indicates
that you can hit Return at this point and the command will work. In
other words, show
ip route
is a
valid command. The other keywords are optional.
In each section of this book, I emphasize the appropriate
show
commands for the topic. For the topics
covered in this chapter, the following show
commands are extremely useful:
show version
show history
show users
The show
version
command
gives a lot more information than just the version of IOS that the
router is currently running. You will see this command pop up a few
more times later in this book. For now, you can see that it tells us
the router type, the IOS image, the system uptime, the current IOS
version, all the available interfaces, and the amount of memory on
the router:
Router#show version
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-AJS40-L), Version 11.3(5)T, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1998 by cisco Systems, Inc.
Compiled Wed 12-Aug-98 05:53 by ccai
Image text-base: 0x0305770C, data-base: 0x00001000
ROM: System Bootstrap, Version 11.0(10c), SOFTWARE
BOOTFLASH: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c),
RELEASE SOFTWARE (fc1)
Router1 uptime is 1 week, 2 days, 8 hours, 48 minutes
System restarted by reload
System image file is "flash:c2500-ajs40-l_113-5_T.bin", booted via flash
cisco 2520 (68030) processor (revision M) with 6144K/2048K bytes of memory.
Processor board ID 10353279, with hardware revision 00000003
Bridging software.
X.25 software, Version 3.0.0.
SuperLAT software copyright 1990 by Meridian Technology Corp).
TN3270 Emulation software.
Basic Rate ISDN software, Version 1.1.
1 Ethernet/IEEE 802.3 interface(s)
2 Serial network interface(s)
2 Low-speed serial(sync/async) network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
16384K bytes of processor board System flash (Read ONLY)
Configuration register is 0x2102
The show
history
command gives a log of the router commands you have used. The length
of this history log depends on the size set by the terminal history
command. The default is 10 lines.
Router#show history
show history
show terminal
show users
enable
show version
The show
users
command
gives a complete listing of all currently connected users:
Router#show users
Line User Host(s) Idle Location
2 tty 2 steve1 idle
5 tty 5 john2 Async interface 2
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