Cisco’s IOS show command can provide a lot of information. Although most of the time this information is much more the you need, so Cisco has provided a way to pipe the information through filters. Just like on Linux, you can use the pipe (|) to pass the show output to filters and display only the information you need.
The syntax for using the pipe is Show command | filter regular-expression. There are several filters that can be used to display information in different ways.
Began (Show command | began regular-expression):
Example:
ASW1#Show interface | began GigabitEthernet
GigabitEthernet0/1 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet, address is fc99.47c4.1181
Description: Uplink to - R1
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
.
.
.
.
Include (Show command | include regular-expression):
The most useful function is the include filter. This is will show you only lines that match a string that you give it. Say that you want to find the status of the GigabiEthernet ports on your switch, but don’t want to grind through all the lines of a show ip interface brief. If you just pipe it to the include command followed by the word “Interface”, you’ll see something like this.
Example:
ASW1#show interfaces | include GigabitEthernet
GigabitEthernet0/1 is up, line protocol is up (connected)
GigabitEthernet0/2 is up, line protocol is up (connected)
.
.
.
GigabitEthernet0/47 is up, line protocol is up (connected)
GigabitEthernet0/48 is up, line protocol is up (connected)
GigabitEthernet1/1 is up, line protocol is up (connected)
.
.
GigabitEthernet1/4 is down, line protocol is down (notconnect)
TenGigabitEthernet1/1 is down, line protocol is down (notconnect)
TenGigabitEthernet1/2 is down, line protocol is down (notconnect)
Exclude (Show command | exclude regular-expression):
Example:
ASW1#Sho cdp neighbors | exclude SEP
Capability Codes:R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
R3 Gig 1/1 133 R S I WS-C3560X Gig 1/1
R1 Gig 0/1 137 R S I 3845 Gig 0/0
R2 Gig 1/2 156 R S I WS-C3560X Gig 1/1
WAP1 Gig 4/1 130 T AIR-CAP35 Gig 0
WAP2 Gig 4/2 130 T AIR-CAP35 Gig 0
Section (show running-config | section include regular-expression):
Example:
ASW1#show running-config | section include interface
interface FastEthernet0
no ip address
no ip route-cache cef
no ip route-cache
no ip mroute-cache
!
interface GigabitEthernet0/1
description Uplink to - R1
switchport trunk encapsulation dot1q
switchport trunk native vlan 1000
switchport mode trunk
no logging event link-status
speed 100
duplex full
priority-queue out
no snmp trap link-status
no mdix auto
ip dhcp snooping trust
.
.
interface GigabitEthernet1/1
description Uplink to R2
switchport trunk encapsulation dot1q
switchport trunk native vlan 1000
switchport mode trunk
srr-queue bandwidth share 1 30 30 30
srr-queue bandwidth shape 30 0 0 0
priority-queue out
mls qos trust dscp
ip dhcp snooping trust
!
interface Vlan100
no ip address
service-policy input DATA-VLAN
!
interface Vlan500
no ip address
service-policy input VOICE-VLAN
In conclusion Cisco’s show command combined with pipes and filters can reduce the amount of information you need to wade through find what you are looking for therefore saving time and money.
