Show Commands

The best method to appreciate the use of show commands is to display sample output from a Cisco IOS router.

Example 3-6 displays a list of truncated show commands available from the CLI on a Cisco router in PRIV EXEC mode. (Version 12.2 was used to supply this output.)

Example 3-6 show Commands

R1#show ?
access-expression	List access expression
access-lists	List access lists
accounting	Accounting data for active sessions
adjacency	Adjacent nodes
aliases	Display alias commands
arp	ARP table
async	Information on terminal lines used as router
	interfaces
backup	Backup status
bgp	BGP information
bridge	Bridge Forwarding/Filtering Database [verbose]
buffers	Buffer pool statistics
caller	Display information about dialup connections
cef	Cisco Express Forwarding
class-map	Show QoS Class Map
clock	Display the system clock
configuration	Contents of Non-Volatile memory
connection	Show Connection
context	Show context information
controllers	Interface controller status
cops	COPS information
crypto	Encryption module
debugging	State of each debugging option
derived-config	Derived operating configuration
dhcp	Dynamic Host Configuration Protocol status
diag	Show diagnostic information for port
	adapters/modules
dial-peer	Dial Plan Mapping Table for, e.g. VoIP Peers
dialer	Dialer parameters and statistics
dialplan	Voice telephony dial plan
diffserv	Differentiated services
dlsw	Data Link Switching information
dnsix	Shows Dnsix/DMDP information
docsis	Show DOCSIS
drip	DRiP DB
dspu	Display DSPU information
dxi	atm-dxi information
entry	Queued terminal entries
environment	Environmental monitor statistics
exception	exception informations
file	Show filesystem information
flash:	display information about flash: file system
frame-relay	Frame-Relay information
fras	FRAS Information
fras-host	FRAS Host Information
gateway	Show status of gateway
history	Display the session command history

Example 3-6 show Commands (Continued)

hosts	IP domain-name, lookup style, nameservers, and host
	table
html	HTML helper commands
idb	List of Hardware Interface Descriptor Blocks
interfaces	Interface status and configuration
ip	IP information (show ip route follows)
ipv6	IPv6 information
key	Key information
line	TTY line information
llc2	IBM LLC2 circuit information
lnm	IBM LAN manager
local-ack	Local Acknowledgement virtual circuits
location	Display the system location
logging	Show the contents of logging buffers
memory	Memory statistics
mgcp	Display Media Gateway Control Protocol information
microcode	show configured microcode for downloadable hardware
modemcap	Show Modem Capabilities database
mpoa	MPOA show commands
ncia	Native Client Interface Architecture
netbios-cache	NetBIOS name cache contents
ntp	Network time protocol
num-exp	Number Expansion (Speed Dial) information
parser	Display parser information
pas	Port Adaptor Information
pci	PCI Information
policy-map	Show QoS Policy Map
ppp	PPP parameters and statistics
printers	Show LPD printer information
privilege	Show current privilege level
processes	Active process statistics
protocols	Active network routing protocols
registry	Function registry information
reload	Scheduled reload information
rmon	rmon statistics
route-map	route-map information
running-config	Current operating configuration
sessions	Information about Telnet connections
sgbp	SGBP group information
snmp	snmp statistics
spanning-tree	Spanning tree topology
srcp	Display SRCP Protocol information
ssh	Status of SSH server connections
ssl	Show SSL command
stacks	Process stack utilization
standby	Hot standby protocol information
startup-config	Contents of startup configuration
tcp	Status of TCP connections

Example 3-6 show Commands (Continued)

tech-support	Show system information for Tech-Support
terminal	Display terminal configuration parameters
traffic-shape	traffic rate shaping configuration
users	Display information about terminal lines
version	System hardware and software status
vlans	Virtual LANs Information
vtemplate	Virtual Template interface information
whoami	Info on current tty line

This section briefly covers the shaded commands in Example 3-6.

Example 3-7 displays sample output from the most widely used IOS command, show ip route. Example 3-7 show ip route Command

R1#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set

131.108.0.0/16 is variably subnetted, 3 subnets, 2 masks C 131.108.255.0/30 is directly connected, Serial0/0

O 131.108.2.0/24 [110/400] via 131.108.255.2, 00:00:03, Serial0/0

C 131.108.1.0/24 is directly connected, Ethernet0/0

R1#show ip route ?

Network to display information about or hostname Border Gateway Protocol (BGP) Connected

Exterior Gateway Protocol (EGP)

Enhanced Interior Gateway Routing Protocol (EIGRP) Show routes added by DHCP Server or Relay Interior Gateway Routing Protocol (IGRP) ISO IS-IS IP Access list Mobile routes On Demand stub Routes Open Shortest Path First (OSPF) IP routing table profile Routing Information Protocol (RIP) Static routes Summary of all routes Show supernet entries only

Hostname or A.B.C.D bgp connected egp eigrp dhcp igrp isis list mobile odr ospf profile rip static summary supernets-only

Example 3-7 show ip route Command (Continued)

Display routes from a VPN Routing/Forwarding instance Output modifiers

R1#show ip route ospf

131.108.0.0/16 is variably subnetted, 3 subnets, 2 masks O 131.108.2.0/24 [110/400] via 131.108.255.2, 00:00:30, Serial0/0

Example 3-7 displays three IP routing entries. The more specific command, show ip route ospf, displays only remote OSPF entries. Every IOS command can be used with the ? character to display more options. In this case, the network administrator used it to identify the ospf option and then typed show ip route ospf to view only remote OSPF entries.

Example 3-8 displays the output from the show ip access-lists IOS command. Example 3-8 show ip access-lists Command

R1#show ip access-lists ?

<1-199> Access list number

<1300-2699> Access list number (expanded range)

WORD Access list name

| Output modifiers

R1#show ip access-lists

Standard IP access list 1

permit 131.108.0.0, wildcard bits 0.0.255.255 Extended IP access list 100

permit tcp any host 131.108.1.1 eq telnet

Example 3-8 enables the network administrator to quickly verify any defined access lists. Example 3-8 includes two access lists, numbered 1 and 100.

Use the show debugging command to display any debug commands in use. This verifies whether any debugging is currently enabled.

Example 3-9 displays the sample output when debug ip routing is enabled. Example 3-9 show debugging Command

R1#show debugging IP routing:

IP routing debugging is on R1#undebug all

All possible debugging has been turned off

Currently, the router in Example 3-9 is enabled for debugging IP routing. To turn off the debugging, apply the undebug all command, as shown in Example 3-9. This command ensures that all debug options are disabled. You can specify the exact debug option you want to disable with the no option; for example, to disable the IP packet option, the IOS command is no debug ip packet.

To display the hardware interfaces on the router, use the show interfaces command to explore the physical and statistical state.

Example 3-10 displays the show interfaces command on a router named R1. Example 3-10 show interfaces Command

R1#show interfaces
Ethernet0/0 is up, line protocol is up
Hardware is AmdP2, address is 0002.b9ad.5ae0 (bia 0002.b9ad.	5ae0)
Internet address is 131.108.1.1/24
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usee,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopbaek not set
Keepalive set (10 see)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:01, output hang never
Last clearing of "show interface" counters 00:00:05
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
1 packets input, 366 bytes, 0 no buffer
Received 1 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
3 packets output, 202 bytes, 0 underruns(0/0/0)
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
Serial0/0 is up, line protocol is up
Hardware is PowerQUICC Serial
Internet address is 131.108.255.1/30
MTU 1500 bytes, BW 256 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation FRAME-RELAY, loopback not set
Keepalive set (10 sec)
LMI enq sent 0, LMI stat recvd 0, LMI upd recvd 0, DTE LMI	up
LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0
LMI DLCI 0 LMI type is ANSI Annex D frame relay DTE
Broadcast queue 0/64, broadcasts sent/dropped 1/0, interface	broadcasts 1

Example 3-10 show interfaces Command (Continued)

Last input 00:00:02, output 00:00:00, output hang never Last clearing of "show interface" counters 00:00:07

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops) Conversations 0/1/256 (active/max active/max total) Reserved Conversations 0/0 (allocated/max allocated) Available Bandwidth 192 kilobits/sec 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 2 packets input, 86 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 2 packets output, 86 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 output buffer failures, 0 output buffers swapped out 0 carrier transitions DCD=up DSR=up DTR=up RTS=up CTS=up

Ethernet0/1 is administratively down, line protocol is down

Hardware is AmdP2, address is 0002.b9ad.5ae1 (bia 0002.b9ad.5ae1) MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) ARP type: ARPA, ARP Timeout 04:00:00 Last input never, output never, output hang never Last clearing of "show interface" counters 00:00:10 Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 input packets with dribble condition detected 0 packets output, 0 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 0 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Example 3-10 displays a router with two Ethernet interfaces and one serial interface. Interface Ethernet 0/0 is enabled and is currently running packets over the wire, while Ethernet 0/1 is not enabled. Interface Serial 0/0 is configured for Frame Relay and the physical layer (Layer 1) details are displayed. Other possible physical states are as follows:

■ Ethernet0/1 is up, line protocol is up—The Ethernet interface is active, sending and receiving Ethernet frames.

■ Ethernet0/1 is up, line protocol is down—The Ethernet interface is cabled but no keepalives are received, and no Ethernet frames are sent or received (possible cable fault).

■ Ethernet0/1 is administratively down, line protocol is down—The Ethernet interface is not enabled administratively; typically an interface is not enabled for connectivity as yet.

■ Ethernet 0/1 is down, line protocol is up—A physical condition is not possible. The protocol is up only if the physical state of the line is up. The IOS image will never report this condition because it is not a possible state of any IOS interface.

To display the system log (syslog), use the show logging command. Example 3-11 displays sample output taken from a router named R1.

Example 3-11 show logging Command R1#show logging

Syslog logging: enabled (0 messages dropped, 0 messages rate-limited, 0 flushes, 0 overruns)

Console logging: level debugging, 27 messages logged Monitor logging: level debugging, 0 messages logged Buffer logging: level debugging, 1 messages logged Logging Exception size (4096 bytes)

Trap logging: level debugging, 31 message lines logged Log Buffer (60000 bytes): 2d20h: %SYS-5-CONFIG_I: Configured from console by console 2d20h: %CLEAR-5-COUNTERS: Clear counter on all interfaces by console

Example 3-11 shows that 27 messages have been logged and that the logging level is debugging, which entails the following log message types:

■ Emergencies—System is unusable (severity = 0)

■ Alerts—Immediate action needed (severity = 1)

■ Critical—Critical conditions (severity = 2)

■ Warnings—Warning conditions (severity = 4)

■ Notifications—Normal but significant conditions (severity = 5)

■ Informational—Informational messages (severity = 6)

■ Debugging—Debugging messages (severity = 7)

Two messages have also been displayed on the terminal: the first message is a configuration change, and the second appears when a PRIV EXEC user has cleared the counters on all the interfaces.

The show route-map command displays any policy route maps configured. Policy route maps override routing decisions on Cisco routers. Route maps basically allow an administrator to change or modify a router to override the current IP routing table entries. The only caveat of this is that the show ip route command does not show the administrator routes following a route map. The show route-map command can be used instead.

The show version command displays the system's hardware configuration, the software version, the names and sources of configuration files, and the boot images. Issue the show version EXEC command to accomplish this. Example 3-12 displays sample output.

Example 3-12 show version Command on R1 R1#show version

Cisco Internetwork Operating System Software

IOS (tm) C2600 Software (C2600-IK8O3S-M), Version 12.2(2)T, RELEASE SOFTWARE (f c1)

TAC Support: http://www.cisco.com/cgi-bin/ibld/view.pl?i=support

Copyright 1986-2001 by cisco Systems, Inc.

Compiled Sat 02-Jun-01 15:47 by ccai

Image text-base: 0x80008088, data-base: 0x813455F8

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

ROM: C2600 Software (C2600-IK8O3S-M), Version 12.2(2)T, RELEASE SOFTWARE (fc1)

R1 uptime is 2 days, 20 hours, 15 minutes

System returned to ROM by reload at 14:57:18 UTC Mon Mar 1 1993

System restarted at 10:00:02 UTC Mon Mar 1 1993

System image file is "flash:c2600-ik8o3s-mz.122-2.T.bin"

cisco 2611 (MPC860) processor (revision 0x203) with 61440K/4096K bytes of memory

Processor board ID JAD043000VK (1947766474)

M860 processor: part number 0, mask 49

Bridging software.

X.25 software, Version 3.0.0.

2 Ethernet/IEEE 802.3 interface(s)

32K bytes of non-volatile configuration memory.

16384K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

Example 3-12 displays a number of key components and identifies the hardware installed on the router. For example, the Cisco IOS software version is 12.2T, the router's uptime is 2 days, 20

hours, 15 minutes, and the memory installed on the router is 64 MB. There is 16 MB of System Flash, and the current configuration register is 0x2102.

NOTE The alias command allows you to create a custom shortcut to an IOS command so that the EXEC user does not have to type the complete IOS command. In addition to these custom commands that you might define, there are some predefined shortcut commands already. For example, show ip route is already defined in IOS with the shortcut sh ip ro. You can define your own alias with the following global IOS command: alias EXEC alias-name IOS-command

View the predefined aliases with the following command:

Router#show aliases

EXEC mode aliases:

h help lo logout p ping r resume s show u undebug w where

For example, you could make the command ospf display only OSPF routes by issuing the following command:

alias EXEC ospf show ip route ospf

Continue reading here: Debugging Cisco Routers

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