L2 concepts

[vinoth13.c]

i have two vlans vlan 100 and 101 , both are connected in  different L2 switch ..vlan 100 and 101 having different subnet , they need to communicate each other .

we dont have l3 switch and router . 

how to do that ?

canyone help me ..

thanks

[vivek srivastava]

If subnet is different and switches are L2, then you can't communicate between two VLANs

[Joseph W. Doherty]

Hosts on the two VLANs might be able to intercommunicate if you interconnect the two VLANs and if your hosts don't have gateways. (Without gateways, hosts should ARP for all IPs, and so you can exchange packets if ARP resolves.)

[Joseph W. Doherty]

I did a little more research on this. What I described may or may not work. It also depends on whether a host, without a default gateway, considers its active/connected network interface as a default for all other networks. If it does, it should ARP, and as long as different networks are within the same broadcast domain (such as interconnecting two VLANs), other network hosts should "see" and respond to the ARP. However, if the host does not consider its active/connected network interface as a default, then it shouldn't ARP for hosts other than on its "own" network.

[Richard Burts]

Joseph's suggestion to interconnect the vlans may make it possible for all the devices to communicate with each other. But let us acknowledge one thing - when you interconnect the vlans you no longer really have two vlans you actually have one big vlan with two names. Remember that the basic definition of a vlan is that the vlan defines a broadcast domain. When you interconnect the vlans you create one large broadcast domain.

HTH

Rick

[Joseph W. Doherty]

Rick is entirely correct.

Further, if what I suggests works, not only do we have effectively one VLAN, there's not much advantage having two networks either.

I hope the OP's question is some kind of puzzle, i.e. not something to be used in a production network.

[Richard Burts]

Joseph makes a good point that the original post sets up a situation with mutually contradictory requirements. A network built with only layer 2 switches can not effectively communicate between two vlans. If the requirement is for several vlans and for them to communicate then the network must provide layer 3 switches or routers. If the requirement is for just layer 2 switches then the network must provision only one vlan.

HTH

Rick

[Julio E. Moisa · Accepted solution]

Hi,

In this case you always need a L3 device: router, multilayer switch or firewall. Now you could try using 1 VLAN and create the second network as secondary, for example:

vlan 100

name Hybrid

interface vlan 100

no shutdown

ip address 192.168.100.1 255.255.255.0

ip address 192.168.101.1 255.255.255.0 secondary. 

Are you using the computers without gateway?