How to gather packet captures in pcap format on a router?

There are various ways to capture the packets on Cisco router here let see how we configure and then capture the packets required in pcap format.

Fig 1.1- Cisco IOS Embedded Packet Capture 1

Step1: Configure Capture ACL

!

ip access-l ext list

 permit tcp any any eq 80

 permit tcp any eq 80 any

!

Step2: Create a Traffic Policy

!

conf t 

ip traffic-export profile capout mode capture 

bidirectional 

length 512 

incoming access-list list 

outgoing access-list list 

exit

!

Fig 1.2- Cisco IOS Embedded Packet Capture-2

Step3: Apply the profile to interface

!

interface gi0/1 [Egress interface where you need to capture]
ip traffic-export apply capout size 300000
exit 

!

Step4: To start(and stop) packet capture -exit from config prompt

!

traffic-export interface gi0/1 clear - before starting
traffic-export interface gi0/1 start - before testing
traffic-export interface gi0/1 stop - stop after the test 

!

Step 5: Save is to flash and via tftp

!

traffic-export interface gi0/1 copy flash: 

!

or 

!

traffic-export interface gi0/1 copy tftp:

!