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View Full Version : Subnet prefixes in Figures 3.18 and 3.19


gizmo24
01-01-2009, 12:28 PM
I'm having some troubles interpreting the subnet prefixes used in LAB_A and LAB_B in the IP Address Problems 1 & 2 shown in figures 3.18 and 3.19.

Both figures include a model 1900 switch in LAB_A which has two LAN segments labelled F0/27 and F0/26. Do the numbers following the forward slashes represent switch port numbers or IP subnet prefixes?

The second question deals with the subnet prefixes used by the F0/0 router interfaces in both LAB_A and LAB_B as shown in figure 3.18.

In order for the interfaces on both routers to have a network block of 32 (as stated in the text) and the interface in LAB_B to be the broadcast address of subnet 192.168.1.64, both IP addresses must have a prefix of /27 (and mask of 255.255.255.224). The prefix seems to be implied.

I believe that figure 3.18 (and figure 3.19 with a different prefix) should be modified to indicate that both IP addresses have a prefix of /27:

192.168.1.62/27
192.168.1.95/27

lammle
01-01-2009, 02:36 PM
the f0/26 and f0/27 are the port numbers.
This is the reason why hands-on experience is SO important when studying. You need to get some routers and switches and play with them.
And you are correct that the /27 is implied.
cool
Cheers!
Todd

lildeezul
01-01-2009, 04:59 PM
to interpret the meaning.

Fa0/27 = fast ethernet, slot 0 / port number 27

fa3/5 = fast ethernet, slot 3 / port number 5