how to configure point to point network ?

[00uq7mz54kga8M6tI5d6]

How to do

How to do the Network-B ? 

[Harold Ritter]

Hi @00uq7mz54kga8M6tI5d6 ,

Point to point in this context means that the subnet needs to provide just enough addresses for the two routers on the link. Using a /30 would fulfill the requirement. For example you could use 192.168.45.0/30 (192.168.45.1/30 on Calgary fa0/1 and 192.168.45.2/30 on Surrey fa0/1).

Regards,

[Joseph W. Doherty]

As Harold correctly notes, /30s, traditionally, have been used for p2p networks, but on later equipment, sometimes /31s can be used for p2p too.  (NB: the reason for using /31s over /30, you can define twice as many p2p networks.)

[Harold Ritter]

Hi Joseph,

Longtime no speak. Hope you are doing well. Good point regarding the /31. The reason I mentioned /30 rather than /31, which I normally prefer, is that this seems to be a Cisco Packet Tracer scenario and I doubt that CPT supports /31. I completely agree that /31 would be a better fit though.

Regards,

[00uq7mz54kga8M6tI5d6]

What is the subnet mask for network-b ?

[Giuseppe Larosa]

Hello @00uq7mz54kga8M6tI5d6 ,

a /30 subnet has a subnet mask of 255.255.255.252     that means only two bits for the host portion.

see last two bits in the following way:

00 subnet

01 first host

10 second host

11 broadcast

Hope to help

Giuseppe

[00uq7mz54kga8M6tI5d6]

could you explain in more detail ?

[00uq7mz54kga8M6tI5d6]

in my exercise, the correct IP address is not 192.168.45.1/30 on Calgary fa0/1 and 192.168.45.2/30 on Surrey fa0/1. the subnet mask 255.255.255.252 is correct. I don't understand what the first IP address available is?

[Joseph W. Doherty]

A /30 network has four addresses.  The first is usually reserved for the network's prefix, itself, the next two addresses are host addresses, and the last address is the network broadcast address.

Networks also need to be on specific boundaries, again in blocks of 4.

192.168.45.0/30 comprised of:
192.168.45.0
192.168.45.1
192.168.45.2
192.168.45.3

192.168.45.4/30 comprised of:
192.168.45.4
192.168.45.5
192.168.45.6
192.168.45.7
etc.

With a network block, the "first" address is the next after the one also used by the network prefix.

BTW, with a p2p, generally it makes no difference which end uses which host address.