Sometimes, I have to face such a situation that I need to quickly and explicitly know whether a full length VLAN packet can traverse between two RJ45 ports.
Yes, I mean 802.1Q ethernet frame with Etype=81 00 (diagram below).
What I can do now is: Get two Windows PCs, for each PC, intall Intel Gigabit NIC and Intel specific driver to create a virtual NIC, with VLAN ID=3 assigned.
Then connect the two PCs to each of the two RJ45 port.
Finally execute ping to generate a full-length ethernet packet.
ping -f -l 1472 <dest-IP>
This way, I can be sure that the sent packet has the maximum "IP data payload" of 1500 bytes(8 bytes of ICMP header and 1472 bytes of ICMP data).
If the ping gets reply, I know that the ethernet channel support full-length VLAN packet.
From my experiment, some home switch or broad band routers(e.g. Linksys WRT54G) does not support full-length VLAN packet switching, so only
ping -f -l 1468 succeeds.
You see, I have to use an expensive Intel NIC to carry on that test, quite inconvenient. You know, for most laptop today, they do not equip an Intel NIC, and, even it is an Intel NIC, Intel VLAN driver, Intel has limitations on the models on which VLAN driver can be installed.
So, my question is: Is there a small program that can let me send a full-length VLAN packet without installing a dedicated VLAN driver? Or better, the program has a stock feature that does the very job for my situation.
Windows programs preferred, Linux solution welcome. Simpler the program, the better. Thank you.
The Linksys router bought around year 2006 uses official firmware v7.00.6. (linksys web admin image)
[2012-11-09] This technique can be quite useful. The ethernet channel to check can be something more interesting, e.g., a 802.11 WDS bridge .