Segmentation wrongly done

[Mykematt]

I am new to cisco and learning networking. But the different vlans I created can't communicate with each other, and I can't seem to find the problem. What should I post here inorder to enable you to assist in locating the problem?

[Flavio Miranda]

hi

 Lets start by your devices.  Which device do you have? model and version.

Keep in mind that inter vlan communication is done by a router or a switch Layer 3.  You can not perform inter vlan communication with Layer 2 switches.

[Mykematt]

Okay, I have a 2960-24TT Switch, and I think it is layer 3, although I am unsure. The reason I think so, is that I have two networks on my workstation, the first works fine, i.e., its vlans can communicate with one another, and the switch I used is also a 2960-24TT. I created a second network, which I want to connect to the first one with a multilayer switch, and this second network is where the problem is. I'll just post a screenshot to help clarify my point.

[Flavio Miranda]

You can share you PacketTracer file here if you want. You just need to zip it first.  As per the topology, you can perform intervlan communication in both topologies. You just need to configure it right.

 The topology on the left, you need to configure trunk between switch and router. You dont need to use two cable, only one is enough.

 Then, you need to configure sub interface on the router.

Basics command:

int gix/x.100

encapsulation dot1q 100

ip add 192.168.100.1 255.255.255.0

On the switch, you just need to add vlan 100

vlan 100

and configure the interface as trunk

inter fast X

switchport mode trunk

[Mykematt]

Thanks, but the configuration for the left network was intentional. I wanted to learn how to configure in both access and trunk modes. So, on the one on the left, I used the access mode, hence the two wires. For the one on the right, I used the trunk mode, hence the one wire. Now, the one on the left works fine: intervlan communication works. The problem is with the one on the right: intervlan communication is not working. Attached is the packet tracer file as requested. 

[Flavio Miranda]

For the topology on the right, you dont need encapsulation dot1q. 

You did almost everything right, except that you did not create the vlans on the Multi layer switch.

If you look at your file they will be down, just like this:

Vlan1 unassigned YES unset administratively down down

Vlan11 192.168.11.1 YES manual down down

Vlan12 192.168.12.1 YES manual down down

Vlan13 192.168.13.1 YES manual down down

Vlan14 192.168.14.1 YES manual down down

Vlan50 192.168.100.2 YES manual down down

After you create the vlan on the L3 switch with the command  "vlan 12", "vlan 11", etc

you are going to see this:

Vlan1 unassigned YES unset administratively down down

Vlan11 192.168.11.1 YES manual up up

Vlan12 192.168.12.1 YES manual up up

Vlan13 192.168.13.1 YES manual up up

Vlan14 192.168.14.1 YES manual up up

Vlan50 192.168.100.2 YES manual up up

HQCoreswitch#

You also need the command "ip rouing"

and then you can ping from one pc to another

C:\>ping 192.168.14.1

Pinging 192.168.14.1 with 32 bytes of data:

Reply from 192.168.14.1: bytes=32 time<1ms TTL=255

Reply from 192.168.14.1: bytes=32 time=1ms TTL=255

Reply from 192.168.14.1: bytes=32 time<1ms TTL=255

Reply from 192.168.14.1: bytes=32 time=1ms TTL=255

Ping statistics for 192.168.14.1:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

Minimum = 0ms, Maximum = 1ms, Average = 0ms

C:\>

[Mykematt]

Hi Flavio, and thanks for your assistance. However, can you walk me through your process, so I can learn?

First, I did try to perform the IP route on the multilayer switch, but it tells me that the hop address is an IP on the router itself. So, how did you do the Ip Routing command?

Second, how did you create vlan on the L3 switch? I think I already did that (or rather I created interface vlans), which is why it shows that they were all down. I tried to switch them on but couldn't. So it seems there is something I needed to do in addition to creating int vlans on the L3 switch.

[Jon Marshall · Accepted solution]

The command to enable routing on a L3 switch (if it is not enabled by default) is simply "ip routing" and because the L3 vlan interfaces (SVIs) are all on the switch there is no need for any "ip route ... " statements so no need for a next hop IP. 

A vlan is a L2 concept so to create a vlan on a switch it is - 

switch(config)# vlan <vlan ID>
switch(config-vlan)# name <name>

once you have done the above you can then assign ports into those vlans or add the vlans to trunk links. 

To route between vlans you then need to create the SVIs ie. 

switch(config)# int vlan <vlan ID>
switch(config-vlan)# ip address <ip address> <subnet mask>  

for the SVI to show as up/up you need one of two things to happen so either - 

1) an access port is assigned to the vlan and the port is up/up 

or 

2) the vlan is assigned to a trunk link and the trunk link must be up/up. 

Jon

[Mykematt]

Thank you very much. I really appreciate it.