Cisco ASA and IOS-XE embedded packet capturing

This is a short post about a step-by-step procedure to configure packet capturing on Cisco ASA or IOS XE using the CLI.

Cisco ASA embedded packet capturing:

access-list acl_capin extended permit ip host 217.100.100.254 host 10.0.255.254
access-list acl_capin extended permit ip host 10.0.255.254 host 217.100.100.254
capture capin interface inside access-list acl_capin

or

capture capin interface inside match ip host 10.0.255.254 host 217.100.100.254
[possible in asa 8.x and later]

Show captured packets:

asa-1(config)#  show capture capin

10 packets captured

   1: 15:11:12.760092       10.0.255.254 > 217.100.100.254: icmp: echo request
   2: 15:11:12.761755       217.100.100.254 > 10.0.255.254: icmp: echo reply
   3: 15:11:12.764196       10.0.255.254 > 217.100.100.254: icmp: echo request
   4: 15:11:12.765615       217.100.100.254 > 10.0.255.254: icmp: echo reply
   5: 15:11:12.768072       10.0.255.254 > 217.100.100.254: icmp: echo request
   6: 15:11:12.769354       217.100.100.254 > 10.0.255.254: icmp: echo reply
   7: 15:11:12.771612       10.0.255.254 > 217.100.100.254: icmp: echo request
   8: 15:11:12.773077       217.100.100.254 > 10.0.255.254: icmp: echo reply
   9: 15:11:12.775548       10.0.255.254 > 217.100.100.254: icmp: echo request
  10: 15:11:12.777150       217.100.100.254 > 10.0.255.254: icmp: echo reply
10 packets shown

asa-1(config)#

asa-1(config)#  show capture capinside detail

20 packets captured

   1: 15:11:12.760092 a000.0000.0001 a000.0000.0021 0x0800 Length: 114
      10.0.255.254 > 217.100.100.254: icmp: echo request (ttl 255, id 5)
   2: 15:11:12.761755 a000.0000.0021 a000.0000.0001 0x0800 Length: 114
      217.100.100.254 > 10.0.255.254: icmp: echo reply (ttl 255, id 5)
   3: 15:11:12.764196 a000.0000.0001 a000.0000.0021 0x0800 Length: 114
      10.0.255.254 > 217.100.100.254: icmp: echo request (ttl 255, id 6)
   4: 15:11:12.765615 a000.0000.0021 a000.0000.0001 0x0800 Length: 114
      217.100.100.254 > 10.0.255.254: icmp: echo reply (ttl 255, id 6)
   5: 15:11:12.768072 a000.0000.0001 a000.0000.0021 0x0800 Length: 114
      10.0.255.254 > 217.100.100.254: icmp: echo request (ttl 255, id 7)
   6: 15:11:12.769354 a000.0000.0021 a000.0000.0001 0x0800 Length: 114
      217.100.100.254 > 10.0.255.254: icmp: echo reply (ttl 255, id 7)
   7: 15:11:12.771612 a000.0000.0001 a000.0000.0021 0x0800 Length: 114
      10.0.255.254 > 217.100.100.254: icmp: echo request (ttl 255, id 8)
   8: 15:11:12.773077 a000.0000.0021 a000.0000.0001 0x0800 Length: 114
      217.100.100.254 > 10.0.255.254: icmp: echo reply (ttl 255, id 8)
   9: 15:11:12.775548 a000.0000.0001 a000.0000.0021 0x0800 Length: 114
      10.0.255.254 > 217.100.100.254: icmp: echo request (ttl 255, id 9)
  10: 15:11:12.777150 a000.0000.0021 a000.0000.0001 0x0800 Length: 114
      217.100.100.254 > 10.0.255.254: icmp: echo reply (ttl 255, id 9)
20 packets shown

asa-1(config)#
Browser capture:
https://10.255.1.203/admin/capture/capin

Download pcap:
https://10.255.1.203/capture/capin/pcap

Disable capture and remove access-list:

no capture capin
no capture capout
clear configure access-list acl_capin
clear configure access-list acl_capout

Cisco ASR embedded packet capturing:

ip access-list extended acl_cap
 permit ip any any
 permit icmp any any
 exit
 
monitor capture mycap access-list acl_cap 
monitor capture mycap limit duration 1000
monitor capture mycap interface GigabitEthernet3 both
monitor capture mycap buffer circular size 10
monitor capture mycap start
monitor capture mycap export tftp://10.255.1.87/mycap.pcap

Show captured packets:

rtr-2#show monitor capture mycap buffer dump
0
  0000:  A0000000 0004A000 00000001 08004500   ..............E.
  0010:  00640041 0000FF01 A9530A00 FF010A00   .d.A.....S......
  0020:  FF020800 0B62000D 00000000 0000001E   .....b..........
  0030:  72BDABCD ABCDABCD ABCDABCD ABCDABCD   r...............
  0040:  ABCDABCD ABCDABCD ABCDABCD ABCDABCD   ................
  0050:  ABCDABCD ABCDABCD ABCDABCD ABCDABCD   ................
  0060:  ABCDABCD ABCDABCD ABCDABCD ABCDABCD   ................
  0070:  ABCD                                  ..

1
  0000:  A0000000 0001A000 00000004 08004500   ..............E.
  0010:  00640041 0000FF01 A9530A00 FF020A00   .d.A.....S......
  0020:  FF010000 1362000D 00000000 0000001E   .....b..........
  0030:  72BDABCD ABCDABCD ABCDABCD ABCDABCD   r...............
  0040:  ABCDABCD ABCDABCD ABCDABCD ABCDABCD   ................
  0050:  ABCDABCD ABCDABCD ABCDABCD ABCDABCD   ................
  0060:  ABCDABCD ABCDABCD ABCDABCD ABCDABCD   ................
  0070:  ABCD                                  ..
...

rtr-2#show monitor capture mycap buffer
 buffer size (KB) : 10240
 buffer used (KB) : 128
 packets in buf   : 14
 packets dropped  : 0
 packets per sec  : 1
...

Disable capture and remove access-list:

monitor capture mycap stop
no monitor capture mycap
no ip access-list extended acl_cap

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