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Juniper Monitoring Interface Traffic
 
You want to look at the headers of packets transiting an interface to debug protocol operation.
Use the monitor traffic command:
 
# run monitor traffic interface ge-1/0/1
[It will monitor the interface all incoming and outgoing traffic]
 
# run monitor traffic interface fe-1/0/1 size  1492  detail
 
The monitor traffic command is equivalent to the Unix tcpdump command and is useful for watching protocol traffic on an interface when attempting to debug a problem. This recipe watches all traffic on interface fe-1/0/1, which is an interface in an OSPF backbone area (area 0.0.0.0). The default packet size for the monitor traffic command is 68 bytes, which captures the beginning of packet headers, but not much more. We specify a packet size of 1,492 bytes, which is the maximum OSPF packet size.
 
Type Ctrl-c to end the monitoring.
 
One disadvantage of monitoring interface traffic is that it uses a lot of the Routing Engine's CPU and can degrade performance on the router.
 
 
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