what is the defference between these interfaces

Answered Question
Nov 8th, 2009

dear experts,

what is the defference between these interfaces? S0, S0/0, S0/0/0

thanks for your urgent reply

I have this problem too.
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Correct Answer by Joseph W. Doherty about 7 years 1 month ago

If you go back to an old 2500 module, you might see that its serial port in built directly into the box, much as its Ethernet port. So the box has Ethernet 0 and serial 0.

On more recent routers that have replaced the 2500 series such as the 2800 series, serial ports aren't directly built into the box, instead there may be multiple module slots. When you place a multiple port card in such slots (e.g. HWIC-4T, see http://www.cisco.com/en/US/prod/collateral/modules/ps5949/ps6182/product_data_sheet0900aecd80274416.html), to identify an individual port, you need to identify both the slot and the port. One reason for this, i.e. where you just don't number all ports in sequence, since not all modules slots have to be used and when they are used they might host a different number of ports, other port numbers are not impacted.

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Joseph W. Doherty Sun, 11/08/2009 - 05:43

Number of zeros? (Just kidding.)

Interface numbering depends on the architecture of the device. If there's just a main serial port, it would be numbered such as serial 0, serial 1, etc. If there's some kind of module that the port resides in, the first number would be module number and the second number the port number within the module, i.e. serial 0/0, serial 0/1, serial 1/0, serial 1/1, etc. Some devices have even more layers of architecture to identify the port, and for those you might have serial 0/0/0 or serial 1/0/3, etc.

labibmakar Sun, 11/08/2009 - 06:16

dear josephdoherty, thanks alot for your reply, would you like please explain this sentence you wrote above to me? (Some devices have even more layers of architecture to identify the port)what is meant by more layers of the architecture?, thanks alot for your help

Correct Answer
Joseph W. Doherty Sun, 11/08/2009 - 06:36

If you go back to an old 2500 module, you might see that its serial port in built directly into the box, much as its Ethernet port. So the box has Ethernet 0 and serial 0.

On more recent routers that have replaced the 2500 series such as the 2800 series, serial ports aren't directly built into the box, instead there may be multiple module slots. When you place a multiple port card in such slots (e.g. HWIC-4T, see http://www.cisco.com/en/US/prod/collateral/modules/ps5949/ps6182/product_data_sheet0900aecd80274416.html), to identify an individual port, you need to identify both the slot and the port. One reason for this, i.e. where you just don't number all ports in sequence, since not all modules slots have to be used and when they are used they might host a different number of ports, other port numbers are not impacted.

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