Trunk Port Vs Access Port

trunolimit
Building a reputation

Trunk Port Vs Access Port

Hello All,

 

I come from a cisco IOS background. On IOS you'd have 4 Switchport options

 

dynamic desirable 

dynamic auto

access

trunk

 

If you set up a port as a trunk port and plugged a client that does not support dot1q tags you wouldn't get any traffic going through that port. Further more you could control wether or not the port autonegotiated to a Trunk if it saw a DTP packet come through.

 

Fast forward to Meraki and You've only got 2 options, Trunk and Access. There are some bnetwork devices that are capable of reading Frames with intact VLAN tags. On IOS I would just put it into Trunk mode and I'd know for a fact if that device can read VLAN tags or not because it would work or it wouldn't.

 

I can't do that on Meraki becasue I have no way of knowing if a Trunk port autonegotiated to Access mode (the VLAN tags are stripped on egress) or if it's an ACTUAL Trunk port (VLAN tags are not stripped on egress). 

 

Does Access port and Trunk port just fundimentally mean different things in the MEraki world? Access means only a single VLAN alowed while Trunk just means multiple VLANs are allowed? 

 

Rant: Has anyone here been through a CCNA or any kind of Cisco training? Why can't meraki (or do they already?) offer a similar comprehensive training where you are taken down to the packet level and shown exactly how meraki habdles traffic and best practices. The meraki training I've gotten is just GUI click this to do this and that. No explination of what the router or switch is actually doing under the hood. 

6 REPLIES 6
jdsilva
Kind of a big deal

Trunk and Access mean exactly the same thing on an MS as they do on a Catalyst. Meraki MS do not support DTP so the two dynamic modes are not available, and a connected neighbour will not be able to negotiate the switchport mode so it will default to its default (which varies by catalyst model).

trunolimit
Building a reputation

I guess my confusion comes from if I plug in a computer to a Trunk port on a catalyst the computer doesn't work. This is expected behaviour since a User end device wouldn't be expected to read 802.1q tagged frames. But if I plug that same computer into a Meraki Trunk port it works just fine.

So my conlcusion was that Access port in Meraki means Access port but Trunk actually means Trunk AND Also Access port in that it will strip VLAN tag on egress if it sees the device attached does not read 802.1Q.

jdsilva
Kind of a big deal

If you plug a computer into a trunk port then it would function on whatever VLAN is set to the native VLAN. This behaviour doesn't differ between Catalyst or MS. 

BrandonS
Kind of a big deal

So on Catalyst when you create a trunk port maybe it has no native VLAN at default?  I thought VLAN 1 would be native at default.

jdsilva
Kind of a big deal

Yup, VLAN 1 is the default native VLAN on Catalyst. 

 

What is different is the STP settings. Catalyst is just a normal port which will go through listening/learning before forwarding. MS will try and detect if there's an STP capable device or an end device connected, and transition to forwarding in 2 seconds (I think, not 100% sure but it's fast). 

Nash
Kind of a big deal

So MS acts a bit like Portfast, just with less risk of loop and a bit more intelligence.

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