VLAN
in [Linux Networking]
|
Prev: help connecting to my linux machine with verizon dsl via ssh
Next: Samba: nmbd/nmbd_namequery.c:query_name_response messages
From: spip_yeah on 28 Sep 2006 12:54 Hello, Is it necessary to have a VLAN capable NIC in order to have a linux box participate in a VLAN, or can 802.11q be entirely emulated in sofware at the driver level? The following thread almost answered the question, but it is still not quite clear to me: http://groups.google.com/group/comp.os.linux.networking/browse_thread/thread/bbbe30a3f12f62a8/1f7f8c22e9b56c9e?lnk=gst&q=VLAN&rnum=8#1f7f8c22e9b56c9e Thank you, Spip
From: Allen Kistler on 28 Sep 2006 14:18 spip_yeah(a)yahoo.com wrote: > Hello, > > Is it necessary to have a VLAN capable NIC in order to have a linux box > participate in a VLAN, or can 802.11q be entirely emulated in sofware > at the driver level? > > The following thread almost answered the question, but it is still not > quite clear to me: > > http://groups.google.com/group/comp.os.linux.networking/browse_thread/thread/bbbe30a3f12f62a8/1f7f8c22e9b56c9e?lnk=gst&q=VLAN&rnum=8#1f7f8c22e9b56c9e It depends on what you want to do. If you want the Linux machine to be the VLAN switch, then VLAN switching is done in software. vconfig can do this for Linux, although I've never played with it myself. (vconfig is distributed with Fedora, at least, and possibly others.) If you just want the Linux machine to be on a VLAN, then the whole purpose of VLANs is that they are LANs. Nothing but the switch knows that the LAN is virtual. You can also connect the Linux machine to a VLAN switch on a VLAN trunk and define multiple virtual interfaces on the Linux machine to make the the machine effectively multihomed even if it only has a single physical interface. In no case is the hardware 802.11q-aware.
From: Pascal Hambourg on 28 Sep 2006 14:58 Hello, spip_yeah(a)yahoo.com a ?crit : > > Is it necessary to have a VLAN capable NIC in order to have a linux box > participate in a VLAN, or can 802.11q be entirely emulated in sofware > at the driver level? On Linux IEEE 802.1Q tagging/untagging is done by software in the module 8021q. I have used it on cheap Realtek ethernet cards which I believe do not have special provisions for it. However some ethernet cards (or their driver, I don't know), are unable to send and/or receive frames with a 1504-byte data length needed to transport tagged frames with a 1500-byte payload. Therefore, VLAN interfaces created on top of such cards with vconfig are limited to a MTU/MRU of 1496. An example is the DEC 21041 (module tulip).
From: spip_yeah on 2 Oct 2006 13:49
Pascal Hambourg wrote: > However some ethernet cards (or their driver, I don't know), are unable > to send and/or receive frames with a 1504-byte data length needed to > transport tagged frames with a 1500-byte payload. Therefore, VLAN > interfaces created on top of such cards with vconfig are limited to a > MTU/MRU of 1496. An example is the DEC 21041 (module tulip). That's very useful info. Thanks. Do you know if there is a compilation, somewhere, of what drivers are known to be aware of the adjusted payload size they must do with? To sum it up: participating in a VLAN does not require a VLAN-capable NIC at all. Being the switch for a VLAN requires VLAN support either in hardware or software, so a VLAN-capable NIC is still not mandatory, correct? One more question: is it not possible that a non VLAN-capable NIC will drop tagged frames (by considering them as invalid frames) before the software interface is even gets to look at them? Thanks! Spip. |