VLSM Issue

[EdgarAllanPoe]

Hi!

Sorry if this post is in the wrong section.

Anyway, I've been banging head against the wall with this all and hoped that someone could tell me what I was doing wrong. I've used VLSM calculators but the configurations don't work.

So...here it is. I attached the lab, and the problem I'm having is with Part 2 and 3, the IPv4 addressing.

This is what I came up with...

Device: PC-A
IP Address: 192.168.0.129    
Subnet Mask: 255.255.255.224
Gateway: 192.168.0.158

Device: R1-G0/0
IP Address: 192.168.0.158
Subnet Mask: 255.255.255.224     
Gateway: N/A

------------------

Subnet B

Device: R1-G0/1
IP Address: 192.168.0.126
Subnet Mask: 255.255.255.128        
Gateway: N/A

Device: S1(VLAN1)
IP Address: 192.168.0.125
Subnet Mask: 255.255.255.128
Gateway: N/A

Device: PC-B
IP Address: 192.168.0.1
Subnet Mask: 255.255.255.128
Gateway: 192.168.0.126

But this configuration does not work. I'm not looking for someone to do my homework or anything, but I just can't tell what I've done wrong. All the lights go green, but I can't ping anything. All the interfaces are on. The ones that need to be anyway. So it has to be addressing, I think. Am I making a stupid mistake?

[Matt Delony]

Hello EdgarAllanPoe,

I looked at the assignment and it looks like it wants you to start subnet A from 192.168.0.0 (subnet 0) for 30 hosts, then subnet B for 126 hosts after that. I think you reversed the subnet assignment (subnet B starts at 192.168.0.0). This is packet tracer assignment looks like, so I'm not sure if pings will fail if you do the subnetting in a reversed order.

For troubleshooting this kind of problem in general, I would recommend checking the following:

• Verify that correct links are connected between the devices
• Verify that links are in up/up state with "show interface x/y"
• For S1, validate that links have proper VLAN in STP forwarding state for F0/5 and F0/6 with "show spanning-tree". I would expect F0/5 and F0/6 to be in designated forwarding state based on this topology.
• For R1, verify that routing table has routes to the proper subnets with "show ip route". I would expect to see routes for 2 directly-connected subnets
• For PC-A and PC-B make sure that they are on and their NIC's are enabled and properly configured.

When you ping to hosts in same subnet, you should expect to see complete ARP entry with IP address and mac address.

Try pinging from R1 to PC-A. Does it succeed? What does "show ip arp" on R1 reveal after attempting the ping? Is there an entry populated for PC-A's IP address or does it say 'incomplete'?

[Georg Pauwen]

Hello,

post your Packet Tracer project file (ZIP the .pkt file first otherwise you cannot upload it)...