serial IPs

Easy..

/30 means 4 IP-addresses in the subnet, the first one is the network address (wire address), the last is the broadcast address, so you can use 2 addresses. You only need two addresses, so why would you create a network that is bigger than two adresses??

schreef in bericht news: snipped-for-privacy@p79g2000cwp.googlegroups.com...

Hi!

Because addresses 192.168.16.113/30 and 192.168.16.145/30 are part of subnets 192.168.16.96/27 and 192.168.16.128/27 that are in use on other interfaces.

Michael

The question is asking "the most efficient ip addressing".

Yes, we read that also. I'm curious to know what your point is.

The original poster was aware that "/30" is more efficient than "/27" and someone else has explained that the other two "/30" addresses fall within address blocks already in use.

BernieM

How is "/27" more efficient for the serial interfaces? It's a point-to-point connection .. only 2 host IP addresses are required. Why waste a "/27" when a "/30" will do fine ... that's what being more efficient means.

BernieM

With "/30" how do you provide for the 4 host addresses needed when working in a Frame-Relay WAN that has two "redirection" points?

The serial link is point-to-point ... only 2 host addresses are needed.

BernieM

You really need to stop reading between the lines. It's a CCNA level question. Have another look at the diagram.

There is a point-to-point link between two routers. We know they are routers because the diagram is using the router icon. There is no 'switch'. Based on all the information given, remember, don't go inventing things that just aren't there, it's simple asking what is the most efficient IP addressing scheme for one of the serial interfaces.

Think point-to-point'. How many host addresses do we need? Two. What's the most efficient way of providing a '2 host' block? Using a '30-bit' mask.

Of the three 30-bit mask addresses available two fall within subnets already in use ... leaving the correct answer being "192.168.16.193/30".

BTW .. the answer you chose is also already in use:

"192.168.16.158/27" .. has host id of '30' in the '192.168.16.128 / 27' .. the subnet defined on the right.

BernieM

But the choice you made is already in use on one of the routers other interfaces. Which is the router in question? What information identifies a specific router? The answer could be applied to either router. Each router only has 1 serial interface. The other interfaces are Ethernet as depected by the 'Ethernet' symbol.

The question isn't asking you to alllow for future growth. The diagram clearly shows a point-to-point link.

I'm sorry but i've already marked you paper incorrect. Please return to your studies.

BernieM