Hi Again everyone, I couldnt let this issue go, so I decided to do some more testing (Again please feel free to test it out to confirm). I tried to create a SPAN session to capture data through the trunk link to see what data ran on what vlan. Had a hard time getting the NIC of my monitor host not to discard the vlan tagged frames. In the end i created a trunk between a Linux workstation and a 3560 switch. Again, i set the native vlan to 250, i only allowed vlan 200 on the trunk.. My findings are this:
- CDP runs on vlan 1, no matter what. - STP runs on the vlan on which the instance is at.. Ie.. STP for vlan 200, runs on vlan 200. - VTP runs on vlan 1, no matter what. - DTP is pretty confusing, since im not getting any tagged frames, so I cant tell how its working. Anyways.. i got the wireshark cap file if anyone wants to take a look at it. Hope its of value to someone else as well.. Sincerely, Kim Pedersen Wouter Prins wrote: > Hi Kim, > > Here's what i have in my notes (i debugged this four months ago > :)): vlan 1 will still be used for control traffic (cdp, vtp, dtp) if > you prune it off the trunk. STP will not work for vlan 1 if you prune > vlan 1 from the trunk. > > 2009/8/20 Kim Pedersen <[email protected] <mailto:[email protected]>> > > Hi Ken, > > But that begs the question, when i state that native vlan should be > 250 on a certain trunk, but i dont allow that on the trunk (switchport > trunk allow vlan 200), to allow only another vlan (200), how does cdp > function? (lab shows that it still finds neighbor devices). > > Kim > > [email protected] <mailto:[email protected]> wrote: > > Hi Kim, > > CDP along with VTP & STP was transported by vlan 1. Vlan 1 need not > > necessary be the native vlan. > > > > Kengyong > > CCIE #24979 > > > > > >> Hi All, > >> > >> I have a question regarding the native vlan in dot1q. Frames > comming > >> from the vlan that is choosen as the native vlan is not tagged > across > >> the trunk. I can manually set the native vlan to be, say 200. I > can then > >> also say that i only want to allow vlan 250 to cross the trunk. > I was > >> under the impression that stuff like CDP used the native vlan > across > >> trunks, but if it is manually pruned (by not allowing it), why > does it > >> still work? > >> > >> Am I wrong in that CDP does not use the native vlan? > >> > >> What I was trying to do was to follow Cisco's guidelines as > to not use > >> the native vlan 1. However, since VTP cant prune vlan 1, I was > doing it > >> manually and came up with this thought... > >> > >> Hopefully someone can clear it up for me. > >> > >> Thanks > >> > >> Sincerely, > >> Kim Pedersen > >> > >> -- > >> > >> // Freedom Matters > >> // Follow my progress on: http://kpjungle.wordpress.com > >> > >> _______________________________________________ > >> For more information regarding industry leading CCIE Lab > training, please > >> visit www.ipexpert.com <http://www.ipexpert.com> > >> > >> > > > > > > -- > > // Freedom Matters > // Follow my progress on: http://kpjungle.wordpress.com > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, > please visit www.ipexpert.com <http://www.ipexpert.com> > > > > > -- > Wouter Prins > [email protected] <mailto:[email protected]> > 0x301FA912 > -- // Freedom Matters // Follow my progress on: http://kpjungle.wordpress.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
