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New Member

Bandwidth on a Serial Interface

Dear All,

I want to know that how to determine actual bandwidth of a serial interface which the provider is giving to us. By default serial interface have 1544 kbps bandwith and its shows interface counters ( tx load , rx load ) according to that timer. If the actual bandwith is 128 kbps then interface counters shows wrong traffic load. "Bandwidht" interface command is usefull when we know the actual bandwith. Is there any way that Router adapt the bandwidth on serial interface from carrier.




Re: Bandwidth on a Serial Interface

show controllers int s0/0 for example will show you the clock speed obtained from the provider (that is if they are providing you the clock from the line).

New Member

Re: Bandwidth on a Serial Interface

Dear romccallum,

Thanks for your support. Show controllers command is helpfull for one of my 3600 series router which shows the clock recieved from provider

line state: up

cable type : V.35 DTE cable, received clockrate 961122

But one another router showsInterface Serial2/0

Hardware is DSCC4

DTE V.35 TX and RX clocks detected.

idb at 0x61ED83FC, driver data structure at 0x61EE07F8

DSCC4 Global Registers:

GCMDR=0x00000000, GSTAR=0x00000000, GMODE=0x000B0005

IQLENR0=0x11111111, IQLENR1=0x00110000

IQCBAR=0x031B7A00, IQPBAR=0x031B78C0

FIFOCR1=0x42104000, FIFOCR2=0xBDEEB800, FIFOCR3=0x0000000F, FIFOCR4=0x08080808


which is not helpfull to determine the clock rate.

Thanks and Regards,


New Member

Re: Bandwidth on a Serial Interface

Hi, What I usually do to determinate the maximum bandwidth allowed by the ISP from Site A to Site B, is monitoring the in/out traffic of Serial Interface from a snmp software like PRTG Traffic Grapher, then copy a large file from a host in site A to another in Site B and the maximum bandwidth that show the PRTG when copy the file is the real bandwidth provided by the ISP.

I hope this can help you.

New Member

Re: Bandwidth on a Serial Interface

is there any chance can we see it in the router because we cant do monitoring on any place and any place

New Member

Re: Bandwidth on a Serial Interface

Hi Mujeeb,

As per your query follow the steps provided below for the bandwidth calculation.

1) Check the show interface output for the intended link and check for the txload and rxload. Let’s consider that it is 1/255.

2) As this will be receive and transmit multiply the value by 2 to get 0.007842.

3) Multiply this value by the link bandwidth say for example 2000 Kbps. This will give a value of 15.684 Kbps.

This will be the link bandwidth utilisation for the interface.



New Member

Re: Bandwidth on a Serial Interface

sir.. I dont understand your reply.. will u pls explain...once more..



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