You are correct. The traffic will flow from the client on VLAN A, across the trunk to the router, get routed, come back across the trunk to the switch then to the client in VLAN B. I know I'll probably get hammered for saying this because it's not *required* to work, but for the most part, you want to have each VLAN representing a separate TCP/IP subnet, and therefore the traffic needs to hit the router anyway to get routed between subnets.
> Does only the initial setup of the conversation go > through the router and the actual traffic flow across > the backplane of the switch? The answer to this is "no". However, if your switch and router are capable, you can configure MultiLayer Switching (MLS). In multilayer switching the switch keeps a cache called the MLS cache. In this cache is kept information about TCP/IP "flows". A flow is a unidirectional communication between two hosts (you can change what the switch considers a "flow", but we won't get into that). If the switch and router in your scenario you laid out are both setup with multilayer switching, here's what would happen: 1) Client A (on VLAN A) would send a packet to Client B (on VLAN B). 2) The switch would get the packet, examine source/destination address and see if it was in the MLS cache. (if it finds it, then jump to step 7) 3) The switch makes a partial MLS cache entry using the info from the packet and sends to the router for routing. 4) The router routes the packet, rewriting Layer 2 info as needed, and sends back to the switch. 5) The switch gets the packet back, uses new dest layer 2 address to look in the CAM and decide which switchport to forward the packet. 6) It uses the newly rewritten layer 2 info from the packet and the destination (outgoing) switchport and completes the MLS cache entry. 7) It forwards the packet out the proper switchport. So as you can see, with MLS configured, the first packet is "routed by the router", then all packets after that in that flow have their layer 2 info rewritten by the switch from the info in the MLS cache and are switched to the proper outgoing port without ever going to the router again, thus they call this "route once, switch many". Hope this helps! Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=24890&t=24887 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
