fa0/0, s0/0/0
 

Hi,

I'm reading up on subnetting in a cisco 'networking basics' book and I
keep running across diagrams that show the IP address of a machine w/
something like FA0/0, S0/0/0 and I can't find what these mean or where
they're explained in the book. I did find them in a table w/ a column
header of 'output interface' but ... that really doesn't help me read
the format.

Any help much appreciated.

Re: fa0/0, s0/0/0
 

Ender <noreply@mail.invalid> writes:
>I'm reading up on subnetting in a cisco 'networking basics' book and I
>keep running across diagrams that show the IP address of a machine w/
>something like FA0/0, S0/0/0 and I can't find what these mean or where
>they're explained in the book. I did find them in a table w/ a column
>header of 'output interface' but ... that really doesn't help me read
>the format.

They are abreviated interface names. FastEthernet 0/0, Serial 0/0/0.

When you have lots of routers/firewalls with lots of interfaces, it
pays to keep track of the important details, like interface names and
IP addresses and the like.

Re: fa0/0, s0/0/0
 

On 2007-08-24 22:53:17 -0500, Doug McIntyre <merlyn@geeks.org> said:

> Ender <noreply@mail.invalid> writes:
>> I'm reading up on subnetting in a cisco 'networking basics' book and I
>> keep running across diagrams that show the IP address of a machine w/
>> something like FA0/0, S0/0/0 and I can't find what these mean or where
>> they're explained in the book. I did find them in a table w/ a column
>> header of 'output interface' but ... that really doesn't help me read
>> the format.
>
> They are abreviated interface names. FastEthernet 0/0, Serial 0/0/0.
>
> When you have lots of routers/firewalls with lots of interfaces, it
> pays to keep track of the important details, like interface names and
> IP addresses and the like.

Well, that kinda helps, F is ethernet, and S is serial, but why the
numbers, and the slashes. I can see F0, or F1, or F2, but why the 0/0
or 0/0/0?

Are there other letters for other media? Or some sort of table on this
anywheres?

Re: fa0/0, s0/0/0
 

Ender <noreply@mail.invalid> writes:
>On 2007-08-24 22:53:17 -0500, Doug McIntyre <merlyn@geeks.org> said:

>> Ender <noreply@mail.invalid> writes:
>>> I'm reading up on subnetting in a cisco 'networking basics' book and I
>>> keep running across diagrams that show the IP address of a machine w/
>>> something like FA0/0, S0/0/0 and I can't find what these mean or where
>>> they're explained in the book. I did find them in a table w/ a column
>>> header of 'output interface' but ... that really doesn't help me read
>>> the format.
>>
>> They are abreviated interface names. FastEthernet 0/0, Serial 0/0/0.
>>
>> When you have lots of routers/firewalls with lots of interfaces, it
>> pays to keep track of the important details, like interface names and
>> IP addresses and the like.

>Well, that kinda helps, F is ethernet, and S is serial, but why the
>numbers, and the slashes. I can see F0, or F1, or F2, but why the 0/0
>or 0/0/0?

Depends on the platform in use, and how they number interfaces on that
platform. The simplest, smallest platforms like an old ancient 2501 or
an 8xx series just have single #s. S0, S1, E0, A0. Bigger platforms
that take modular cards tend to seperate out with slashs. So 0/0 is
the card in slot0, the 1st interface on that card. Or, 0/0/0 could be
the card in slot0, the WIC in spot 0 on the card in slot0, and the first
interface on that WIC. If you get up to the BFR or 10k, you get one
more layer deep, combine that with a channelized controller and a
subinterface, and you can have things like 0/5/1/6:0.16.

You'll get a feel for it while just using a cisco router. Nothing
magical about it. Ie. if you have a computer with a few hundred hard
drives attached you'd get lost pretty quickly trying to figure out
which particular hard drive is number 84. Lot easier to figure out
which controller, shelf, and drive number in the shelf. Same sort of thing.

>Are there other letters for other media? Or some sort of table on this
>anywheres?

Its not really that important, they are just short abbreviations.
Ethernet
FastEthernet
GigabitEthernet
Serial
HSSI
ATM
Loopback

Can't think of any other types of interfaces that regularly get
abbreviated, although there's quite a few more.

to Serial port not. the digits 0/0/0 means the number of "module/submodule/port" number, when you are logged on a real equipment there could be a different numbering depending of type of router. That is you have first module, first submodule, first Serial or Fast ethernet port of router.