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Saturday, January 25, 2014

How is the Packet Capture Done on CUCM Appliance Model?

When troubleshooting in Cisco Unified Communications Manager, it is sometimes necessary to collect packets which are being sent to and from the network interface on a CUCM server. What are the process to capture on CUCM appliance model?

1. Starting the Capture 

To start the capture, establish a secure shell (SSH) session to the CUCM server authenticating with the Platform Administrator account:
1a.  Command Syntax
     The command is "utils network capture" and the syntax is as follows:

utils network capture [options]
options  optional   
page,numeric,file fname,count num,size bytes,src addr,dest addr,port
num,host protocol addr

options are:
- pause output
numeric               - show hosts as dotted IP
file fname            - output the information to a file
Note: The file will be saved in platform/cli/fname.cap
fname should not contain the "." character
count num             - a
count of the number of packets to capture
    Note: The maximum count
for the screen is 1000, for a file is 100000
size bytes            -
the number of bytes of the packet to capture
    Note: The maximum
number of bytes for the screen is 128
          For a file it can be
any number or ALL
src addr              - the source address of the
packet as a host name or IPV4 address
dest addr             - the
destination address of the packet as a host name or IPV4 address
num              - the port number of the packet (either src or dest)
protocol addr    - the protocol should be one of the following:
ip/arp/rarp/all. The host address of the packet as a host name or IPV4
address. This option  will display all packets to and fro that address.
Note: If "host" is provided, do not provide "src" or "dest"

1b.  Capturing all traffic
     For a typical capture, one might wish to collect ALL packets of ALL sizes from and to ALL address into a capture file called 'packets.cap'.  To do this simply execute on the admin CLI 'utils network capture eth0 file packets count 100000 size all'


1c.  Capturing based on port number
Troubleshooting a communications issue with Cluster Manager, it might be desireable to capture based on a specific port (8500) using the port option.

Note: For more information about which services require communications on each port, refer to the TCP and UDP Port Usage Guide for the applicable version of CUCM. 
1d.  Capturing based on host
In troubleshooting an issue with CUCM and a particular host, it may be necessary to use the 'host' option to filter for traffic to and from a particular host.  
Note: it may be necessary to exclude a particular host, in this case use  a "!" in front of the IP.    An example of this would be "utils network  capture eth0 file packets count 100000 size all host ip !"

2.  Reproduce the problem symptom or condition

While the capture is running reproduce the problem symptom or condition so that the necessary packets are included in the capture.  If the problem is intermittent it may be necessary to run the capture for an extended period.  If the capture ends, it is because the buffer is filled, restart the capture and the previous capture will be automatically renamed so the previous capture should not be lost.   If a capture is needed for an extended period of time, it might be worthwhile to capture at the network level via other means such as using a monitor session on a switch.

3.  Stopping the capture

To stop the capture hold the Control key and press C on the keyboard.  This will cause the capture process to end and no new packets will be added to the capture dump.

Once this is complete there will be a capture file stored on the server in the location 'activelog platform/cli/'

4.  Collecting the capture from the server.

Collecting the capture from the server is the final step.  The capture files will be stored in "activelog platform/cli/" location on the server.  One can transfer the files through CLI to an SFTP server or to the local PC using the Real Time Monitoring Tool (RTMT).

4a.  Transfer capture file through the CLI to an SFTP server
          Use the command "file get activelog platform/cli/packets.cap" to collect the packets.cap file to  the SFTP server.
     Alternatively to collect all .cap files stored on the server, use 'file get activelog platform/cli/*.cap'
     Finally, fill in the SFTP server IP/FQDN, port, username, password, and directory information:
     The CLI should indicate success or failure of the file transfer to the SFTP server.

4b.  Transfer capture file to local PC using the Real Time Monitoring Tool (RTMT)
            This option will not be available to servers running a 5.x CUCM version earlier than 5.1(1), or 6.x version earlier than 6.1(2).  See CSCsg13820 and CSCsm76349 for details.

          Launch the Real Time Monitoring Tool.  If it is not installed on the local PC, install the appropriate version from the CUCM Administration page Applications->Plugins menu. Click "System", then "Trace & Log Central", then double click "Collect Files".  Click "Next" through the first menu.

     In the second menu choose the checkbox for "Packet Capture Logs" on the server which the capture was performed, then click Next.
     On the final screen choose a time range when the capture was performed, and a download directory on the local PC:

     RTMT will close this window and proceed to collect the file and store it on the local PC in the specified location.

Citation - This blog post does not reflect original content from the author. Rather it summarizes content that are relevant to the topic from different sources in the web. The sources might include any online discussion boards, forums, websites and others.

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