Finding the right piece of information that you need from a
Cisco router can often be a challenge. For example, if you use the show running-config command on a large
production router, you can easily end up with 25 pages of text output.
Locating that one piece of information you’re looking for
can take a lot of time. Once you find it, you might need to make a change, only
to have to rerun the command and go through the whole process again.
However, there are some shortcuts you can take to find this
information more quickly. Let’s looks at some filtering options you can use
when maneuvering through long command output on a Cisco router.
Filter output using line numbers
You can use the show
running-config linenum command to configure the system to include line
numbers at the start of each line in the output. Here’s an example:
Current configuration : 59161 bytes
1 : !
2 : ! Last configuration change at 09:25:35 CDT Tue Aug 16 2005 by root
3 : ! NVRAM config last updated at 09:25:36 CDT Tue Aug 16 2005 by root
4 : !
5 : version 12.3
6 : service tcp-keepalives-in
7 : service tcp-keepalives-out
8 : service timestamps debug datetime msec localtime show-timezone
9 : service timestamps log datetime msec localtime show-timezone
10 : service password-encryption
Once you have line numbers to use as reference points, you
can then filter the output by starting at a certain line or only returning a specified
line. Here’s an example of starting the output at a specific line:
Router# show running-config linenum | begin 6 :
6 : service tcp-keepalives-in
7 : service tcp-keepalives-out
8 : service timestamps debug datetime msec localtime show-timezone
9 : service timestamps log datetime msec localtime show-timezone
10 : service password-encryption
Here’s an example of requesting only one line returned in
the output:
Router# show running-config linenum | include ( 6 : )
6 : service tcp-keepalives-in
Filter output using Include, Exclude, or Begin
You can also use certain commands to help filter your
output. For example, you can use the include
command to see only lines that include the word service. Here’s an example:
Router# show running-config | include service service tcp-keepalives-in service tcp-keepalives-out service timestamps debug datetime msec localtime show-timezone service timestamps log datetime msec localtime show-timezone service password-encryption
You can use the begin
command to start the output at a certain line (such as an interface). Here’s an
example:
Router# show running-config | begin interface Serial3/0 interface Serial3/0
description MPLS T-1
bandwidth 1544
ip address 10.0.100.2 255.255.255.252
no ip proxy-arp (truncated)
In addition, you can use the exclude command in the same way if there’s something particularly
long that you don’t need to see in the output.
The best thing about these three commands is that they work
with almost any output on the router. For example, let’s say I wanted to see
all routes that begin with the IP address 10.83.x.x. But it doesn’t work if I
use this:
Router# show ip route 10.83.0.0 % Subnet not in table
However, if I use something like the following example, I
can see all of the routes that begin with 10.83.x.x:
Router# show ip route | include 10.83. O 10.83.100.8/30 [110/2370] via 10.83.100.2, 05:32:27, Serial1/2:0.83 O 10.83.100.4/30 [110/2115] via 10.20.100.2, 05:32:27, Serial1/2:0.2 C 10.83.100.0/30 is directly connected, Serial1/2:0.83 O 10.83.103.0/24 [110/2195] via 10.83.100.2, 05:32:27, Serial1/2:0.83
Filter output by interface
On the other hand, if you only need to see the output of one
specific interface, you can also filter output in that way. Here’s an example:
Router# show running-config interface Serial3/0 Building configuration... Current configuration : 209 bytes !
interface Serial3/0
description MPLS T-1
bandwidth 1544
ip address 10.0.100.2 255.255.255.252
no ip proxy-arp
no ip mroute-cache
no fair-queue
no cdp enable end
Start searching your output
Did you know that you can search directly from the show running-config command’s output? If
you use the show running-config command,
you should see a –More– prompt at the end of each page of output (depending on
your page length).
If you enter a forward slash [/] at this prompt, it will
replace the prompt with the slash, and you can then type in whatever you want
to search for. Press [Enter], and it will say filtering and then begin showing you the results of your search. (This
is exactly how the UNIX pg command
works.) Here’s an example:
/interface Serial3/0 filtering... interface Serial3/0
description MPLS T-1
bandwidth 1544
ip address 10.0.100.2 255.255.255.252
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David Davis has worked
in the IT industry for 12 years and holds several certifications, including
CCIE, MCSE+I, CISSP, CCNA, CCDA, and CCNP. He currently manages a group of
systems/network administrators for a privately owned retail company and
performs networking/systems consulting on a part-time basis.
