The best method to appreciate the use of show commands is to display sample output from a Cisco IOS router.
Example 4-6 displays a list of truncated show commands available from the CLI on a Cisco router in PRIV EXEC mode.
Example 4-6 show Commands
access-expression access-lists accounting adjacency aliases arp async backup bgp bridge buffers caller cef class-map clock configuration connection context controllers cops crypto debugging derived-config dhcp diag dial-peer dialer dialplan diffserv dlsw dnsix docsis drip dspu dxi entry environment exception file flash:
frame-relay fras fras-host gateway history
List access expression List access lists
Accounting data for active sessions Adjacent nodes Display alias commands ARP table
Information on terminal lines used as router interfaces
Bridge Forwarding/Filtering Database [verbose] Buffer pool statistics
Display information about dialup connections
Cisco Express Forwarding
Show QoS Class Map
Display the system clock
Contents of Non-Volatile memory
Show context information
Interface controller status
State of each debugging option
Derived operating configuration
Dynamic Host Configuration Protocol status
Show diagnostic information for port adapters/modules
Dial Plan Mapping Table for, e.g. VoIP Peers
Dialer parameters and statistics
Voice telephony dial plan
Data Link Switching information
Shows Dnsix/DMDP information
Display DSPU information atm-dxi information
Queued terminal entries
Environmental monitor statistics exception informations
Show filesystem information display information about flash: file system
FRAS Host Information
Show status of gateway
Example 4-6 show Commands (Continued) hosts html idb interfaces ip ipv6 key line llc2 lnm local-ack location logging memory mgcp microcode modemcap mpoa ncia netbios-cache ntp num-exp parser pas pci policy-map ppp printers privilege processes protocols registry reload rmon route-map running-config sessions sgbp snmp spanning-tree srcp ssh ssl stacks standby startup-config tcp tech-support terminal traffic-shape
IP domain-name, lookup style, nameservers, and host table
List of Hardware Interface Descriptor Blocks Interface status and configuration IP information (show ip route follows) IPv6 information Key information TTY line information IBM LLC2 circuit information IBM LAN manager
Local Acknowledgement virtual circuits Display the system location Show the contents of logging buffers Memory statistics
Display Media Gateway Control Protocol information show configured microcode for downloadable hardware Show Modem Capabilities database MPOA show commands
Native Client Interface Architecture NetBIOS name cache contents Network time protocol
Number Expansion (Speed Dial) information Display parser information Port Adaptor Information PCI Information Show QoS Policy Map PPP parameters and statistics Show LPD printer information Show current privilege level Active process statistics Active network routing protocols Function registry information Scheduled reload information rmon statistics route-map information Current operating configuration Information about Telnet connections SGBP group information snmp statistics Spanning tree topology Display SRCP Protocol information Status of SSH server connections Show SSL command Process stack utilization Hot standby protocol information Contents of startup configuration Status of TCP connections Show system information for Tech-Support Display terminal configuration parameters traffic rate shaping configuration continues
Example 4-6 show Commands (Continued)
users version vlans vtemplate whoami
Display information about terminal lines System hardware and software status Virtual LANs Information Virtual Template interface information Info on current tty line
This section briefly covers the highlighted commands in Example 4-6. Example 4-7 displays sample output from the most widely used IOS command, show ip route. Example 4-7 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
184.108.40.206/16 is variably subnetted, 3 subnets, 2 masks C 220.127.116.11/30 is directly connected, Serial0/0
O 18.104.22.168/24 [110/400] via 22.214.171.124, 00:00:03, Serial0/0
C 126.96.36.199/24 is directly connected, Ethernet0/0
R1#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
list IP Access list mobile Mobile routes odr On Demand stub Routes ospf Open Shortest Path First (OSPF)
profile IP routing table profile rip Routing Information Protocol (RIP)
static Static routes summary Summary of all routes supernets-only Show supernet entries only vrf Display routes from a VPN Routing/Forwarding instance
I Output modifiers
R1#show ip route ospf
188.8.131.52/16 is variably subnetted, 3 subnets, 2 masks O 184.108.40.206/24 [110/400] via 220.127.116.11, 00:00:30, Serial0/0
Example 4-7 displays three IP routing entries. The more specific command, show ip route ospf, only displays remote OSPF entries. Every IOS command can be used with the ? character to display more options. In this case, the network administer used it to identify the ospf option and then typed show ip route ospf to view only remote OSPF entries.
Example 4-8 displays the output from the show ip access-lists IOS command. Example 4-8 show ip access-lists
R1#show ip access-lists ?
<1-199> Access list number
<1300-2699> Access list number (expanded range)
WORD Access list name
I Output modifiers
R1#show ip access-lists
Standard IP access list 1
permit 18.104.22.168, wildcard bits 0.0.255.255 Extended IP access list 100
permit tcp any host 22.214.171.124 eq telnet
Example 4-8 enables the network administrator to quickly verify any defined access lists. Example 4-8 includes two access lists numbered 1 and 100.
Use the show debugging command to display any debug commands in use. This verifies if any debugging is currently enabled.
Example 4-9 displays the sample output when debug ip routing is enabled. Example 4-9 show debugging Command
R1#show debugging IP routing:
IP routing debugging is on R1#undebug all
Currently, the router in Example 4-9 is enabled for debugging IP routing. To turn off the debugging, apply the undebug all command, as shown in Example 4-9. This command ensures all debug options are disabled. You can specify the exact debug option you want to disable with the no options; 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 4-10 displays the show interfaces command on a router named R1. Example 4-10 show interfaces
Ethernet0/0 is up, line protocol is up --physical status
Hardware is AmdP2, address is 0002.b9ad.5ae0 (bia 0002.b9ad.5ae0)
Internet address is 126.96.36.199/24
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 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 188.8.131.52/30 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 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
Example 4-10 show interfaces (Continued)
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 4-10 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—Ethernet Interface is not enabled administratively; typically an interface not configured as yet.
Ethernet 0/1 is down, line protocol is up—A physical condition is not possible, for example.
To display the system log (syslog), use the show logging command. Example 4-11 displays a sample output taken from a router name R1.
Example 4-11 show logging Command
Syslog logging: enabled (0 messages dropped, 0 messages rate
limited, 0 flushes,
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
Example 4-11 shows that 27 message have been logged and 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 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 access the route manipulation.
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 4-12 displays a sample output.
Example 4-12 show version Command on R1
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 (c) 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
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)
Example 4-12 displays a number of key hardware data about the router. For example, the 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 creates a custom shortcut to IOS commands so the EXEC user does not have to type the complete IOS command. For example, show ip route is already defined in IOS with the shortcut sh ip ro (not an alias command but rather a shortcut command). You can define your own alias with the global IOS command: alias EXEC alias-name IOS-command
View the predefined aliases with the following command:
EXEC mode aliases:
h help lo logout p ping r resume s show u undebug un 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
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