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Old 07-30-2010, 04:30 PM
Jeroen1000 Jeroen1000 is offline
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Default VLAN: Can't access switch anymore

I'm stumped about getting this to work so I hope someone can lend a hand.

I don't even know how to begin explaining but I'll try. I have read the VLAN articles but I still can't figure this out.

My switch, a Cisco SLM2008, has become unreachable. No ping, no webinterface. Its management "interface" is in VLAN 1.

The setting that caused this is, is called "acceptable frame type". I set this to "tagged only". Two other strange options I have left unchecked:
Enable Tx Force Untag (was unchecked by default)
Enable Ingress Filter (was checked by default)

My network layout:

Switch port 1 (VLAN 1, VLAN2) ------- > Draytek router port 3 (VLAN 1)

Draytek router port 2 (VLAN 1) ------> regular "dumb" switch port 1

My desktop is conntected to the "dumb" switch.

So, I'm thinking the switch rejects my traffic because the traffic comming from my desktop is untagged. However, port 2 of the Draytek is in VLAN 1. Sinde my desktop is conntected to a switch which is conntected to port 2, I would have thought the Draytek would tag the frame?

Anyway, I'm just speculating and help is more than welcome!

Last edited by Jeroen1000; 07-30-2010 at 04:33 PM.
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Old 07-30-2010, 08:36 PM
Jeroen1000 Jeroen1000 is offline
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Alright, I've come up with a theory. I just need a way to verify it.

I think the Draytek does not understand what a trunk port is. I believe it UNTAGS the frame before sending it to the Cisco switch. And since the trunk on the Cisco side will not accept untagged frames, I have a total lockout.

Simplest way to 'unlock' this situation (apart from resetting the switch) would be to connect the Draytek to another port on the Cisco which still accepts untagged frames. But unfortunately, I can't do that. The Cisco is POE powered and it can only draw its power from the special POE port.

A laptop would come very in handy now!

Does anyone know of a way to confirm my suspicions? Certainly I would like to regain access, but then I would still need to find out why this isn't working out.
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Old 07-31-2010, 09:45 AM
Jeroen1000 Jeroen1000 is offline
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small update: after reviewing more Draytek documentation, I now know this router is unable to support a trunk. It can be reached via SSH so I assume I can create a trunk but I don't know yet how to. I've asked Draytek whether they want to consider helping me on this.
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