I have cisco WS-C3650-48TS SW version 03.03.05SE as L3, i need to monitor the traffic on a trunk port?

How much bandwidth its consuming?

2 Answers 2


The show interface command will give you 5 minute input and output bandwidth

Switch# show interfaces gigabitethernet3/0/2
GigabitEthernet3/0/2 is down, line protocol is down (notconnect)
  Hardware is Gigabit Ethernet, address is 2037.064d.4381 (bia 2037.064d.4381)
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Auto-duplex, Auto-speed, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output never, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     0 packets output, 0 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out

If you want to create a graph of the bandwidth, use something like MRTG to set up regular polling of the interface traffic through SNMP. MRTG will create a nice graph of the data i.e.

MRTG graph

To enable PRTG, set up a Read-Only community string on the switch:

snmp-server community <your-community-string> ro

Then configure the device in PRTG using the following settings:

IP Address/DNS Name: IP address of switch
Sensor Management: Automatic device identification (standard, recommended)

Credentials for SNMP Devices:
SNMP Version: 2c
Community String: <your-community-string>

There are other options which allow you to look at the bandwidth of individual traffic flows on a port such as IP accounting and NetFlow, although these do not usually work properly on L3 switches as they rely on traffic being process switched.

  • thanks for the answer, i can see the traffic from the switch itself by sh interface command.
    – Tech
    Aug 6, 2016 at 9:21
  • Can you share, how i can configure snmp with prtg?
    – Tech
    Aug 6, 2016 at 9:34
  • added PRTG info above
    – user27899
    Aug 6, 2016 at 10:19

In order to have a simple view of statistics in terms of pkt that are traversing your trunk port you can build a ACL with a pkt counter and put a filter on the IP or VLAN you are interested in order to count them

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