A Network Engineer was tasked to upgrade the existing switch infrastructure for a site since the current infrastructure does not support PoE for the new project – VoIP and IP enabled CCTV cameras. Upon investigating, he saw that the site has three switches and some ports were not lit up and now needs to know if those ports were lit up last week to help him decide how many switches he really needs to order. Ordering the same amount of switches will drive up the cost, which he is not willing to do since the company is tight with money. Now, the question is, how can he tell that the port is really unused or the people are just on vacation and their PCs are turned off?
There may be tools out there that I am unaware of, but Cisco IOS has a built in show command that you are already familiar with. This is the show interface command. Please look below for the example.
The show command output below was issued on a switch with an uptime of 6 months.
Switch#sh int g0/32 GigabitEthernet0/32 is down, line protocol is down (notconnect) Hardware is Gigabit Ethernet, address is f866.f2fd.c020 (bia f866.f2fd.c020) MTU 1500 bytes, BW 10000 Kbit, DLY 1000 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: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 ! Remaining output were omitted for brevity
The output below is a port with activity.
Switch#sh int g0/24 GigabitEthernet0/24 is up, line protocol is up (connected) Hardware is Gigabit Ethernet, address is f866.f2fd.c041 (bia f866.f2fd.c041) Internet address is 172.30.99.37/30 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, 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 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 ! Remaining output were omitted for brevity
If you compare the line where it says “Last input”, you’ll see that the first show interface command output says “never” while the other one is saying 00:00:00. Since this switch has been up for six months, it is safe to assume that this port hasn’t been used for six months so time to move on to another port and collect the total port count.
Fortunately, the Network Engineer took his time to collect the information and only ordered two switches which saved the company over $6,000! IT, in most companies, do not generate revenue but can definitely help with the company’s bottom line by spending money efficiently and effectively.
I hope this has been helpful and I thank you for reading!
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