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basic understanding with Switches, routers ,Forwarding & Routing


Hi Guys,

    I would like to get some basic understanding with Switches, routers ,Forwarding & Routing

Details :

PC1 :

PC2 :

PC3 :

As per my knowledge,

   1) using a layer 2 switch PC1 & PC3 can communicate because it does not need to go through default gateway & same subnet.

  2) PC1 & PC2 are not able to communicate using layer 2 switches because its different subnet and switch does not do ARP.

  3) PC1 & PC2 can communicate using router since its job to route different subnets

  4) PC1 in vlan 10  & PC2 in vlan 20,we need router have to communication between them,if its say i am using 2 switches it must be config as trunk port not switchport.

Please correct me if i am wrong and if you have additional details.Kindly share.





3 Replies 3

Terry Cheema

1) Correct. Since PC1 and 3 are in same subnet/VLAN, the traffic will be broadcast to all ports in same VLAN, so no need for gateway.

2) Yes if PC1 and PC2 are in different vlan/ broadcast domain, they will need a gateway. So you can have either a Layer 3 Switch (using SVI) or Router to do the inter-vlan routing.

3) Yes as said above you will need a layer 3 device (either a router or a L3 switch) for inter-vlan routing. The way it will work is, lets say PC1(VLAN10) tries to reach PC2(VLAN20), Since ip address of PC2 is not in same subnet, it will be delivered to the default gateway.

4)Yes, if you need to pass on the VLAN tag it needs to be trunk port.


By the way if you post this in LAN, Switching and Routing section you will get lot more views than this. Anyways let me know if you have more questions.


Please rate all helpful posts.

This discussion has been reposted to the LAN, Switching and Routing community.

Terry Cheema,

   Thank you for the reply.

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