CCNA - interface reliability question

Author

interface reliability question

lucus

2003-09-11, 4:49 am

in the show interface output you can see something like this:

reliability x/255 , txload y/255, rxload z/255

my question is this :

how does the router calculate the interface reliability ? what is the exact meaning of txload an rxload ? does the reliability depend in any way of rx and tx ?

Waiting for your opinion. Thanks.

Lamont

2003-09-11, 2:34 pm

I don't have my ICND book in front of me but if I remember correctly reliability is actually something that can be set by the admin, it's not calculated.

Also I believe txload and rxload are gathered from snmp counters on the router....

edmonds_robert

2003-09-12, 9:26 am

The load counters are simply a percentage of the available load that is used on the interface, with 255 equal to 100%. So half would be about 127, for example.

lucus

2003-09-12, 4:17 pm

Thanks for the replies.

I think I found the answer on www.cisco.com:

Load Calculations
The load calculation appears in the displays for this command. The load
is a 5-minute exponentially weighted average that is updated every five
seconds. The load can be adversely affected if the default K values used
to calculate metrics are modified.

Reliability
When PA-A3 input and output error counters increment, they affect the
reliability counter, which indicates the likelihood that a packet will
be successfully transmitted or received. The value is expressed as a
fraction of 255, with a value of 255 indicating a totally reliable link.

router#show interface atm 10/1/0
ATM10/1/0 is up, line protocol is up
Hardware is cyBus ENHANCED ATM PA
MTU 1500 bytes, sub MTU 1500, BW 149760 Kbit, DLY 80 usec,
reliability 249/255, txload 1/255, rxload 1/255

Reliability is calculated using the followi ng formula:

reliability = number of errors / number of total frames

The show interface output displays the average reliability

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