TCP/IP Subnets Question

Question

Here's a question I know the answer to, but I figured I would ask and see how many responses I get and how fast.

I have 2 new PCs to add to a network, their IP addresses are 10.11.12.15 and 10.11.12.16 and the subnet mask is 255.255.255.240.

The problem is that these two machines will not communicate with any other machine on the network, however the other machines are working just fine and can communicate with each other. Additionally, all systems are connected to the same switch, part of the same vlan and the switch's management ip is 30.21.87.245.

What do I need to do to get the PCs to communicate with each other.

Answer 1

10.11.12.16 is a network address and cant be used by a machine...

10.11.12.17 would be the first available address to be used by a machine on the .16 network

which means that 10.11.12.15 would be on a different network.

therefore

10.11.12.1 = network addressfor 1st network

10.11.12.(2-14) = 1st network usable addresses

10.11.12.15 = broadcast address for 1st network

10.11.12.16 = network address for 2nd network

10.11.12.(17-30) = 2nd network usable addresses

10.11.12.31 = broadcast address for 2nd network

haha hopefully thats correct - been a while since ive subnetted vlsm =)

Ummm...change the VLSM mask to 255.255.255.224 so that you can place the two other machines in the same network as the other machines?

OR

place the other two machines in the 2nd network and add a router to your topology to route packets between the network?

HOORAY =d

which answer did you have?

the changing of the subnet mask i assume?

are these questions for industry certs?

Answer 2

Although you didnt really leave enough info to troubleshoot correctly id say Default Gateway..

Answer 3

I would call you and have you come and fix it since you know the answer already :)

Answer 4

Using that subnet mask 10.11.12.15 is the broadcast address for the 10.11.12.1/28 network.

10.11.12.16 is the network address of the 10.11.12.16/28 network.

That's not gonna work!!! :P

If they are meant to be in different VLANs then you would need a router to route packets between VLANs

Answer 5

If you just want the answer, change the subnet mask to 255.255.255.224.