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Capture Cisco CSR packets and Examine with Wireshark


As you know the Cisco’s Cloud Services Router is a virtual router either installed and configured in public Clouds like Amazon Web Services, AWS, or in your private cloud hosted locally. I needed to capture and monitor the traffic on its interfaces with Wireshark. One way I could found is to capture your desired traffic on any interface of CSR, export it to your local disk and open it with Wireshark.
The following procedure can also be used to capture packets on other physical Cisco Routers running following IOS versions.
Cisco IOS Release 12.4(20)T or later
Cisco IOS-XE Release 15.2(4)S – 3.7.0 or later
Lets start capturing traffic here on Cisco CSR.
First we specify the interface to capture the packets on;
csr#monitor capture GIG2 interface GigabitEthernet 2 both
Here GIG2 is any name to create a file and store packets in it, both means to capture both inbound and outbound packets on interface gigabitethernet 2
You can specify ipv4 or ipv6 traffic, select protocol or even sepcify ACL to capture only selected traffic with following command;
csr#monitor capture GIG2 match ipv4 protocol tcp any any
Now we Start the capturing packets on our selected criteria as configured above
csr#monitor capture GIG2 start
The capture is now active. Allow it to collect the necessary data.
After capturing sufficient packets, Stop the capture:
csr#monitor capture CAP stop
Now either you can examine the capture in a summary or detailed view on CSR router itself or export it to your local computer disk and examine with Wireshark.
To examine the capture in a summary view:
csr#show monitor capture CAP buffer brief
Examine the capture in a detailed view:
csr#show monitor capture CAP buffer detailed
Export the capture in PCAP format for further analysis:
csr#monitor capture GIG2 export tftp://10.0.1.11/GIG2.pcap
Once the necessary data has been collected, and exported to tftp server, remove the capture:
csr#no monitor capture GIG2


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