Basic VLAN configuration

[g.kumaran]

sorry for a very basic question. I am working on simulator for Cisco 3500 series Switch. Here is the output of VLAN configurations.

Switch#show vlan brief

VLAN Name Status Ports

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

1 default active Fa0/3, Fa0/4, Fa0/5, Fa0/6

Fa0/7, Fa0/8, Fa0/9, Fa0/10

Fa0/11, Fa0/12, Fa0/13, Fa0/14

600 Engg active Fa0/1

700 RAD active Fa0/2

1002 fddi-default active

1003 token-ring-default active

1004 fddinet-default active

1005 trnet-default active

and earlier, the ports are configured as follows

!

interface FastEthernet0/1

switchport mode access

switchport access vlan 600

!

interface FastEthernet0/2

switchport mode access

switchport access vlan 700

!

I have two PC's connection on Ports Fa 0/1 and Fa 0/2 with IP address as 192.168.1.2/24 and 192.168.1.3/24 respectively. The management VLAN is 1 with IP set to 192.168.1.1/24.

From either of the PC's, I am unable to ping to 192.168.1.1 in VLAN 1. However can able ping these PC's each other? Is this normal or am I doing something wrong or if the Simulator (Boson NetSim Eval) behaves Strangely?

[Prashanth Krishnappa]

You have fa0/1 and fa0/2 in two different VLANs but same IP subnet? This is a misconfiguration. Put them in the same VLAN and you should be able to ping between the two PCs. 3500 XL is a layer 2 switch only and cannot route between VLANs by itself.

[g.kumaran]

confused.. I was thinking that by VLAN, you can implement two different Networks. Hence even if the PC's are of same IP range, they will NOT able to communicate to each other. Am I wrong in that? In that case, Why the PC can't ping to the Swtich management IP which is in VLAN 1? Both the PC's and Management IP is also of the same Subnet (or IP range) but in different VLANs?

btw, I don't expect the 3500 XL to route between VLAN.

[sunil.su.kumar]

Hi Kumaran,

Lets get some basics clear first. VLAN is used to create virtual networks by effective usage of SNM. A host with IP 192.168.1.1 and 192.168.1.128 can be in same subnet if the SNM is 24 and different network if SNM is 25. Based on these we create VLANs.

From u r info 192.168.1.2/24 and 192.168.1.3/24 is effectivly in same network and there is no reason for us to see them in different n/w ( inturn different VLAN). Krishn is correct in saying this is a misconfig.

About not able to ping to 192.168.1.1, how have u configured this. Is this for sc0/sc1 or is it Loopback.

Hope u got this.

Sunil

[g.kumaran]

Thanks Sunil for a proficient explanation.

I would have a clear picture if I know the answer for the following questions.

What is the difference on communication between two different PC's in different subnet (say 192.168.1.100/24 and 192.168.2.100/24)

a) With VLAN

b) Without VLAN?

I presume in both cases, I would be unable to ping each other on a normal L2 Switch as they are of different Subnet.

btw, I configured 192.168.1.1 on the Switch for Management by using the following commands.

!

interface vlan 1

ip address 192.168.1.1 255.255.255.0

no shut

!