Pure L2 switch working

[nitinquiet]

Hi,

I am looking at scenario in which two PC are in different broadcast domain and connected through pure layer2 switch.

Can somebody explain sequence of packets starting from switch is on and how packet can communicate from PC1 to PC2.

PC1 10.10.10.1/24--------Layer2 Switch-----------PC2 20.20.20.1/24

As per my understanding switch learn mac address with help of ARP. But in case of pure L2 switch there is no ARP present on switch, So does this work?

[Jon Marshall]

If the PCs are in different broadcast domains ie. vlans then they cannot communicate in your example. 

You need a L3 device to route between the vlans. 

Jon

[nitinquiet]

But if there is pure L2 switch then it will only look for L2 header. I wanted to understand in deep why and where packet are dropped?

[Jaderson Pessoa]

Here has a good topic talking about your doubt.

Check it: https://learningnetwork.cisco.com/thread/78565

I hope that it can help you.

[Jaderson Pessoa]

You can establish conection between this networks, because they are in diferente broadcast domain, if you need it, apply a L3 devices the will route packets between it.

[Deepak Kumar]

Hi,

Let me try to explain why will it now work?

Layer 1 switch will work on the MAC address table. 

Now PC1 will try to communicate with PC2 

Steps:

1. Here PC2 is on the different subnet so PC1 will run "AND" "OR" operation on TCP and decide to forward the packet on the gateway.

2. Here Destination is L3 know as the gateway so PC1 will lookup his gateway MAC address will broadcast the packet for learning MAC address. Here, there is no gateway so communication will not happing. 

Regards,

Deepak Kumar