Clarification on txload and rxload on serial port for routers

[mahendrasinghmanral]

Hi all,

I have a 1905 series cisco router, when I run "sh int" command it gives me following details -

MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,

     reliability 254/255, txload 7/255, rxload 151/255

  Encapsulation PPP, LCP Open

  Stopped: CDPCP

  Open: IPCP, loopback not set

  Keepalive set (10 sec)

  Last input 00:00:00, output 00:00:00, output hang never

  Last clearing of "show interface" counters 1d21h

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 17

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 918000 bits/sec, 85 packets/sec

  5 minute output rate 45000 bits/sec, 61 packets/sec

     1953638 packets input, 1981536818 bytes, 0 no buffer

     Received 0 broadcasts, 3623874 runts, 0 giants, 0 throttles

     10385026 input errors, 6753254 CRC, 0 frame, 0 overrun, 0 ignored, 7898 abo

Please let me know the significance of txload and rxload.

This router is used for MPLS connectivity.Link is working OK..but I'm not able to understand

exactly what is the above txload and rxload signify.

There is also one peculiar phenomena occuring, when my reliability goes down then rxload also goes down or might be vise versa.

Please tell about this.

Thanks

Mahendra

[Giuseppe Larosa]

Hello Mahendra,

the txload and rxload are an alternate way to express the sent and received traffic rates.

The rtxload and rxload are percentages expressed in fractions with a 255 denominator so in you case you have:

rxload 151/255 to be referred to link speed 1544 kbps =

914,29 kbps

and you see  

5 minute input rate 918000 bits/sec, 85 packets/sec

tx load 7/255 again to be referred to link speed 1544 kbps = 42,38 Kbps

this is another way to say:

5 minute output rate 45000 bits/sec, 61 packets/sec =

As you see the numbers are very close.

The reliability percentage is expressed in terms of a fraction with denominator 255 and 254/255 means that the link is not totally stable .

The percentage expresses the uptime of the link / total time as  successfully received keepalives / total keepalives messages.

When reliability goes down, it is because the OSI layer 2 keepalives have failed for a short time the link has been declared down (IPCP closed, NCP closed), routing protocol may flap, and as a result of this the traffic on the link goes to zero after the fault is detected.

For this reason you see some correlation between downs on reliability and lowering of rxload because they are related.

>> 1953638 packets input, 1981536818 bytes, 0 no buffer

     Received 0 broadcasts, 3623874 runts, 0 giants, 0 throttles

     10385026 input errors, 6753254 CRC, 0 frame, 0 overrun, 0 ignored, 7898 abo

I would not say the link is clean unless you have plugged / unplugged the cable in the last two days.

For further troubleshooting you can follow this troubleshooting guide

http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1915.html

Hope to help

Giuseppe

[Joseph W. Doherty]

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Your counters for input errors, CRC errors and aborts are also indicative of link with some quality issues.