cisco show running-configuration filter

Tired of having to scroll through your whole running-configuration just to read one line at the very end? Cisco has an in built command filter that allows you to specify more accurately what information you want from the running configurations, and mastering these commands not only makes you look like you know what you are doing ,they could save you lots of time and frustration having to look through irrelevant information.

There are mainly three widely used filter in the running config. BEGIN, EXCLUDE and INCLUDE. We can see this issuing the show running-configuration (sh run since we're trying to save time here) followed by the vertical bar key (|). We hit the question mark to see our options.

R1#sh run | ?
append Append redirected output to URL (URLs supporting append operation
only)
begin Begin with the line that matches
exclude Exclude lines that match
include Include lines that match
redirect Redirect output to URL
section Filter a section of output
tee Copy output to URL

The begin command filters through the configuration until it hits the first line that matches whatever word you put in after. Having an understanding of how lines are expressed in the configuration comes in handy when choosing what to type in.

As an example, here is the running-configuration of a router I am currently working on


R1#sh run
Building configuration...

Current configuration : 1238 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
memory-size iomem 5
!
!
ip cef
no ip domain lookup
!
!
!
username R2 password 0 lanwan
!
!
!
interface Serial0/0
no ip address
encapsulation frame-relay
serial restart-delay 0
no dce-terminal-timing-enable
no frame-relay inverse-arp
frame-relay lmi-type ansi
!
interface Serial0/0.2 point-to-point
ip address 10.0.12.1 255.255.255.0
no cdp enable
frame-relay interface-dlci 102
!
interface Serial0/1
ip address 10.1.12.1 255.255.255.0
encapsulation ppp
serial restart-delay 0
no dce-terminal-timing-enable
ppp authentication chap
!
interface Serial0/2
no ip address
shutdown
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial0/3
no ip address
shutdown
serial restart-delay 0
no dce-terminal-timing-enable
!
interface FastEthernet1/0
ip address 172.16.1.1 255.255.255.0
duplex auto
speed auto
!
ip http server
!
ip route 192.168.2.0 255.255.255.0 Serial0/0.2
!
!
no cdp run
!
control-plane
!
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
!
!
end

If we only wanted informatin on the configured static routes, using the begin command we can filter to the exact line.

R1#sh run | begin ip route
ip route 192.168.2.0 255.255.255.0 Serial0/0.2
!
!
no cdp run
!
control-plane
!
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
!
!
end

and we see that this begins the display with the first line that has the words "ip route"

We can use the include command to only display lines that have the words "ip route"

R1#sh run | include ip route
ip route 192.168.2.0 255.255.255.0 Serial0/0.2

This is much more succint output and gives a much neater and pleasing to the eye display.

The Exclude command eliminates all the lines that have the word you put in. For example, if you wanted to remove all the lines that have the word "line".

R1#sh run | exclude line
Building configuration...

Current configuration : 1238 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
memory-size iomem 5
!
!
ip cef
no ip domain lookup
!
!
!
username R2 password 0 lanwan
!
!
!
interface Serial0/0
no ip address
encapsulation frame-relay
serial restart-delay 0
no dce-terminal-timing-enable
no frame-relay inverse-arp
frame-relay lmi-type ansi
!
interface Serial0/0.2 point-to-point
ip address 10.0.12.1 255.255.255.0
no cdp enable
frame-relay interface-dlci 102
!
interface Serial0/1
ip address 10.1.12.1 255.255.255.0
encapsulation ppp
serial restart-delay 0
no dce-terminal-timing-enable
ppp authentication chap
!
interface Serial0/2
no ip address
shutdown
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial0/3
no ip address
shutdown
serial restart-delay 0
no dce-terminal-timing-enable
!
interface FastEthernet1/0
ip address 172.16.1.1 255.255.255.0
duplex auto
speed auto
!
ip http server
!
ip route 192.168.2.0 255.255.255.0 Serial0/0.2
!
!
no cdp run
!
control-plane
!
!
exec-timeout 0 0
logging synchronous
!
!
end

Personally , I prefer the BEGIN and INCLUDE commands as they are more effective. Further more the output of the EXCLUDE command leaves some information hanging and that may be a bit confusing.

configuring cisco catalyst switch VTP modes

VTP (Vlan Trunking Protocol) modes are different ways a switch can be set to share or interact with VTP advertisements. The three modes are Server, client and Transparent.

Server mode is the default setting for Cisco catalyst switches. Within any VTP domain, there must contain at least one switch configured in server mode. When in this mode, the switch can be used to add, modify or delete VLAN related infrormation. These changes are then advertised to other switches in the same domain that are configured as either servers or clients. The receiving switches then compare the revision number from the received update and if the revision number is higher, then it changes its configuration

Client mode is simply a receiver of VTP information configured from a server. when in client mode, no changes can be mad to the switch.

Transparent mode is where a switch will not listen to VTP information being advertised but will pass on the information to other switches. It acts as a standalone device and any VLAN information can be configured.

Configuring the modes:

First we get into the vlan database.

SWITCH#vlan database

We can then type in the vtp command followed by a question mark to see the different options.


SWITCH(vlan)#vtp ?
client Set the device to client mode.
domain Set the name of the VTP administrative domain.
password Set the password for the VTP administrative domain.
pruning Set the administrative domain to permit pruning.
server Set the device to server mode.
transparent Set the device to transparent mode.
v2-mode Set the administrative domain to V2 mode.

for now we shall only concentrate on the three vtp mode options: Server, client and transparent.

To configure as a Server simply type in the vtp server command and you get a notification that the device is switching into server mode.

SWITCH(vlan)#vtp server
Setting device to VTP SERVER mode.

The same goes for configuring as a vtp client.

SWITCH(vlan)#vtp client
Setting device to VTP CLIENT mode.

as well as transparent mode.

SWITCH(vlan)#vtp transparent
Setting device to VTP TRANSPARENT mode

To save and exit into the vlan database, simply type in "exit".

SWITCH(vlan)#exit
APPLY completed.
Exiting....

To verify the VTP mode configured, we can use the "show vtp status" command.

SWITCH#sh vtp status
VTP Version : 2
Configuration Revision : 0
Maximum VLANs supported locally : 256
Number of existing VLANs : 7
VTP Operating Mode : Transparent
VTP Domain Name :
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0x1A 0x47 0x70 0xB8 0xD1 0x2F 0x7E 0x32
Configuration last modified by 10.1.35.2 at 3-1-02 00:48:56


In this instance, the switch is in Transparent VTP operating mode.

Configuring NAT Part 1: Dynamic Translation

NAT was introduced to help resolve the issue of IP Address shortages. With a fast growing number of devices that require an IP Address, many experts predicted that the pool of IP addresses will run out soon. Before a well thought out, long-term solution can be implemented, a few short-term solutions were introduced. Amongst ingenious solutions such as CIDR and Private IP addresses, NAT was introduced.

The term NAT is used by many vendors, and it may differ slightly depending on which equipment you are using to configure NAT. In this blog, we will be exploring NAT used by Cisco IOS.

Here are general steps when configuring a NAT:

• Step 1: Determine inside and outside networks. Label each interface as “inside” or “outside” using the ip nat inside and ip nat outside commands at the interface or subinterface configuration mode.


• Step 2: Ensure that the connectivity exists between the routers. By using either static routes or dynamic routing protocols, make sure that your inside global network can connect to the outside network.


• Step 3: Configure a pool private IP addresses that will be allowed to access the external network


• Step 4: Configure a pool public IP addresses that will be used by your internal network to access the external network


• Step 5: Configure Network Address Translation. Define components that will be translated.


• Step 6: Verify your work

Let's configure the Gateway Router from the below diagram so that the PC's in the internal network can communicate with the devices in external networks.

Step 0: Configure base configuration and assign IP addresses according to above diagram

Router>enable
Router#configure terminal
Router(config)#hostname GatewayRouter
GatewayRouter(config)#interface s0/0
GatewayRouter(config-if)#ip add 216.116.120.250 255.255.255.248
GatewayRouter(config-if)#no shutdown
GatewayRouter(config-if)#int fa1/0
GatewayRouter(config-if)#ip add 10.0.0.1 255.255.255.0
GatewayRouter(config-if)#no shut

Always verify that IP addresses are inputted properly and the Status and Protocol are both up.

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Step 1: Determine inside and outside networks. Label each interface as “inside” or “outside” using the ip nat inside and ip nat outside commands at the interface or subinterface configuration mode.

GatewayRouter#conf t
GatewayRouter(config)#int s0/0
GatewayRouter(config-if)#ip nat outside
GatewayRouter(config-if)#int fa1/0
GatewayRouter(config-if)#ip nat inside

-------------------------------------------------------

Step 2: Ensure that the connectivity exists between the routers. By using either static routes or dynamic routing protocols, make sure that your inside global network can connect to the outside network.

GatewayRouter(config)#ip route 0.0.0.0 0.0.0.0 s0/0

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Step 3: Configure a pool private IP addresses that will be allowed to access the external network

You need to specify the source addresses that will be translated. In this exercise, you will be using an access-list to specify a pool of IP addresses. We will be allowing all internal IP addresses to pass through the gateway router.

GatewayRouter(config)#access-list 1 permit 10.0.0.0 0.0.0.255

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Step 4: Configure a pool public IP addresses that will be used by your internal network to access the external network

Next step is to specify the pool of IP addresses that will be used as Inside Global IP Addresses. Ensure that the pool name specified in the previous command matches the pool name you will be creating in the below command line. Please note that pool name is case-sensitive.

GatewayRouter(config)#ip nat pool OUTSIDE 216.116.120.250 216.116.120.254 net 255.255.255.248

Note that the first IP address marks the starting point of the Inside Global IP Address and the second IP address marks the last Inside Global IP Address to be used for NAT.

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Step 5: Configure Network Address Translation. Define components that will be translated.

GatewayRouter(config)#ip nat inside source list 1 pool OUTSIDE

As you can see there are many options to choose from. Let’s go over the options that we chose.

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Step 6: Verification

The last step is to verify that the Network Address Translation works. You can login to one of your PCs and ping out to the internet. If you have a DNS set up, you can ping a known websites such as google.com or yahoo.com. If your internet network does not have a DNS setup, try to ping an external DNS such as 4.2.2.3. Once you have successfully pinged an external entity, you can revert to GatewayRouter to verify the translation.

Translation is successful. Please note that port number from the output will vary, but the port numbers from Inside global and Inside local will generally match.