Analyze Reliability, Txload and Rxload on Cisco Router or Switch interface

Reliability:

Reliability means the Layer 2 keepalives are sent and received with 0% loss on the link. Reliability of the interface is 255/255 means good news and link is healthy. It is calculated as an exponential average over 5 minutes and as a fraction of 255 (255/255 is 100 percent reliability).

Txload and Rxload:

You can measure transmit and receive traffic on any interface of Cisco Router or Switch. You can find txload and rxload fields of Cisco IOS’s command sh interface <> output and it will be in a number from 0 to 255. You then use that to calculate your bandwidth. txload and rxload roughly measure the amount of traffic passing out of and into an interface, respectively, relative to its perceived bandwidth. As an example, if it is a 100 Mbps Fastethernet interface, txload is 126/255 it means transmit traffic from this interface would be 50 Mbps. If rxload is 63/255 it means receive traffic on this interface would be 25Mbps.

In below example negligible amount of traffic barely registers in the interface statistics (38 kbps out of 100 Mbps is only around 0.038%):

CiscoConsole# sh int fa0/0
FastEthernet0/0 is up, line protocol is up
Hardware is Gt96k FE, address is 0021.a04f.a510 (bia 0021.a04f.a510)
Description: $CiscoConsole$
Internet address is 198.123.159.57/29
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, 100BaseTX/FX
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 00:00:02
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 3000 bits/sec, 1 packets/sec
5 minute output rate 38000 bits/sec, 0 packets/sec
4 packets input, 1575 bytes
Received 3 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog

Note: that the input and output rates shown above are for a 5 minute interval, you can change time interval with the interface configuration command load-interval 30.

CiscoConsole(config)#int fa0/0
CiscoConsole(config-if)#load-interval ?
  <30-600>  Load interval delay in seconds
CiscoConsole(config-if)#load-interval 30
CiscoConsole(config-if)#

Now we can administratively configure an artificially low interface bandwidth; say, 256 kbps. Keep in mind that the bandwidth command modifies only the perceived bandwidth of the interface: it has no effect on the actual speed at which packets are transmitted or received and it will not effect on interface input and output rate.

CiscoConsole(config)# interface f0/0
Ciscoconsole(config-if)# bandwidth 256
 
CiscoConsole#sh int fa0/0
FastEthernet0/0 is up, line protocol is up
Hardware is Gt96k FE, address is 0021.a04f.a510 (bia 0021.a04f.a510)
Description: $CiscoConsole$
Internet address is 198.123.159.57/29
MTU 1500 bytes, BW 256 Kbit, DLY 100 usec,
reliability 255/255, txload 168/255, rxload 25/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, 100BaseTX/FX
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:01, output hang never
Last clearing of "show interface" counters 00:31:53
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
30 second input rate 26000 bits/sec, 22 packets/sec
30 second output rate 169000 bits/sec, 23 packets/sec
14971 packets input, 2483280 bytes
Received 1332 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog

							

Filed Under: Cisco General

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