Simple PC to PC network question

[brianjp2472]

I am trying to get some general information for an upcoming deployment.

Scenario - 2 PC's on the same subnet/VLAN connected to a Cisco catalyst L3 switch. Switch is connected to a router.

PC 1 talks to PC 2.

Does the traffic for PC2 go beyond the switch? Meaning, for example, does the MAC of PC 1 and 2  get put in the routers ARP table as well as the downstream switch?

[Reza Sharifi]

Hi,

Since in your scenario PC1 and PC2 are in the same vlan/subnet, the traffic will stay local to the switch and does not go to the router.

HTH

[brianjp2472]

Thanks Reza - told you it was simple :) One more simple question regarding Wake on Lan. We'll use the same scenario as my original post. My basic understanding of a WOL failure is this:

If PC1 sends a magic packet to PC 2, which has been in a powered down state for longer than the switches ARP table holds entries, the switch will drop the packet, since it would not get its ARP response, and would not wake up. Correct?

If so, are you aware of anything other than static ARP or a DHCP reservation, perhaps some logic on the NIC side of PC 2, that is capable of keeping it ARP entry alive on the switch?

[Reza Sharifi]

As far as I know, there is no ARP involved since the PC and the router/switch have to be on the same segment in order for WOL to work.

HTH

[brianjp2472]

I would have to research this more. I can see where your statement would be true in a subnet-directed transmission method (broadcast). However the unicast method for WoL I can see using ARP tables, which would be vulnerable to ARP resolution failures due to entry expiration.

[Richard Burts]

If a packet is sent as unicast then it normally would need an ARP entry to be able to find the correct MAC address. Most of my experience with WOL has been that the magic packets are sent with broadcast addresses. Is it possible that your WOL server might insert a unicast IP address in the packet but would have its NIC use the MAC broadcast address? That would be a way to get around the need to have an ARP entry.

HTH

Rick