Vlan question

[hanwucisco]

A simple topology, Host A---Switch A---router A--Switch B--host B. both switches are layer2. host A and Host B are in the same Vlan.

When Host sends a packet destinated to host B, it first sends to switch A.

Switch A certain will forward this packet to Router A.

My question is how Switch A knows it goes to router A instead of going some other routes(imagine the topology can be more complex in that swith A attached to many different router or swithc)? there must be some table similar to ARP table.

Similarly, my second question is about the router A, when packet arrives, how does it handle it? it is supposed not using its routing table, isnt?

thanks!

[tbogie_gvds]

Scott,

Thats a great use of the proper terminology. I would like to ask a related question about broadcasts and flooding.

If you had multiple vlans configured on the switch, say Vlan 1, 2, and 3. A host on Vlan 3 sends a unicast to the switch. The switch upon receipt of the frame determines that it does not know the detsination MAC. Will the switch flood the frame through all of the switch ports, or just the ports that are configured for the same VLAN, vlan 3? My educated guess here is that the switch will only flood the frame through ports associated with vlan 3, or otherwise there would be all kinds of issues with VLAN's and security.

Thanks,

Timothy

[scottmac]

I believe you are correct; the switch would flood the frame to all ports of that broadcast domain.

Good Luck

Scott