Hi! First of all, the VLAN implementation follows the 802.1q definitions: http://standards.ieee.org/getieee802/download/802.1Q-1998.pdf So for ultimate reference, use this text as my work with VLANs date of more than six months ;-) You can also try the vlan linux implementation mailing list: vlan@scry.wanfear.com or to suscribe: http://www.WANfear.com/mailman/listinfo/vlan > We printed the first sixteen bytes of the ethernet packet in hard_st_txmit > function but we are unable to see the VLAN proto ID. > It have certain doubts... can you pls clear them ...! > > 1) What happens at the recieve end of the system if it recieves an taged > packet? > (Does it remove the tag before sending it to the upper layer?) VLAN is a feature that works on a lower level than IP (or of any protocol you are using... the VLAN is completelly independent of the protocol you use!). "The addition of a tag header to the frame. This header is inserted immediately following the destina-tion MAC Address and source MAC Address (and routing, if present) fields of the frame to be trans-mitted;" p.62 of reference. That means that the IP paquet will have an extra tagg before being send through the network. So the paquet MUST be detagged before being send to upper layers. > 2) What happens when a tagged packet arrives at a system which does not > have > vlan support? > (Does it drop the packet completly or after doing some processing...!) Well... in that case the system will probably try to interpret the paquet as a tcp/ip paquet (or whatever the protocol is) and it will not recognize it. So it will very probably drop it. > 3) About inserting the priorities .. does it have any significance outside > the > system ...? > (I believe VLAN packet consists of only VLAN protocol ID, VLAN ID and > priority.) > Which priority it is .. whether it is egress or ingress. I don't really get the question. But if you are asking me if the priority you set is valid in a single system or all along the path... the priority will be applied (if applied) depending of the priority part of the header, but also of the VLAN ID. And sometimes a bridge can simply not apply any priority rule! That means that, if what you call system is one computer, the priority CAN have a sens ouside the system. But if your system is a VLAN network, it will not have a sens outside the network. But you may find paquets that are priority-tagged but with no VLAN ID! p.11 of the reference. > 4) How do use ethreal to capture tagged packets? I tired using filters > there > .. didn't work? Help... pls...! I never used Ethereal before. But I find this text in http://www.wcug.wwu.edu/lists/netdev/200005/msg00141.html It is from the programer of the patch I gived you: "Ethereal, and a modified tcpdump, distributed with the VLAN pkg on my page, can snoop/decode the VLAN packets. Ethereal is better and prettier, IMHO :)" So I supose it sould work... A new feature aded since Release 1.5: "Add relatively large change by Nick Eggelston that makes VLAN devices more transparent to tools like tcpdump and other raw packet snoopers. This will only be enabled when the REORDER_HDR flag is set." So think about using tcpdump instead... Good luck!! Guille ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
