Can't configure SPAN on Cisco 800 Series Router

[Michael Murray]

I have a Cisco 881 router running 15.1(4)M4. I am trying to configure SPAN on it to mirror my outside interface (source) to one of my LAN interfaces (dest).

!--- WAN interface

interface FastEthernet4

description Comcast WAN$ETH-WAN$

ip address 5.5.5.1 255.255.255.252

ip nat outside

ip virtual-reassembly in

duplex auto

speed auto

crypto map SDM_CMAP_1

!---LAN interface

interface FastEthernet0

no ip address

rtr(config)#mon session 1 source int f

rtr(config)#mon session 1 source int fastEthernet 4 ?

% Unrecognized command

rtr(config)#mon session 1 source int fastEthernet ?

  <0-4>  FastEthernet interface number

rtr(config)#mon session 1 source int fastEthernet 4 ?

% Unrecognized command

rtr(config)#mon session 1 source int fastEthernet 4

% Incomplete command.

As you can see from the above output there is a problem with the command on this interface. When I try to set Fa0 as my source it works fine:

rtr(config)#mon session 1 source int fastEthernet 0

rtr(config)#

Is this because fa4 is layer 3 and fa0 is a switchport? If so, is there another way to set fa4 as the source?

Thanks,

-mike

[acampbell]

Mike,

You have answered this yourself.

Interface fast 4 is your WAN port and is totally seperate from

interfaces 0-3 which are usually your internal LAN.

I can only suggest that you connect your WAN port fas 4 via a seperste hub or switch

as stop gap to allow you to run a sniffer etc.

Regards,
Alex.
Please rate useful posts.

[cadet alain · Accepted solution]

Hi,

You can use RITE:http://www.cisco.com/en/US/docs/ios/12_4t/12_4t11/ht_rawip.html or EPC:http://yurisk.info/2010/02/01/capture-packets-at-ios-cisco-router-or-finally-we-have-a-sniffer/

Regards

Alain

Don't forget to rate helpful posts.

[Michael Murray]

For reference, here's a good article on configuring RITE:

http://blog.ipexpert.com/2010/07/01/router-ip-traffic-export-rite/

[ashirkar]

Hello Michael,

You can refer this document for EPC

Configuration Example: Embedded Packet Capture on Cisco IOS and IOS XE

HTH

Regards,

Ashish Shirkar

Community Manager-NI