FreeBSD 10.0-R connected to Cisco switch (in 'trunk' mode with native VLAN) - doesn't work?

[David DeSimone]

We use exactly the sort of configuration you showed, and it works perfectly with our FreeBSD systems.

It is possible you are running afoul of spanning-tree behavior on the port.  Access ports are treated as "edge" ports and can activate right away, while trunk ports must go through the full listen/learn/forward cycle before they will start forwarding traffic, making the port appear dead during its first 30-40 seconds.

Consider adding to the 3750 configuration:

    interface GigabitEthernet_/0/__
      spanning-tree portfast trunk

The switch will give you a big warning about why this is a terrible idea, but it is in fact a very good idea, since your server (hopefully) isn't doing any bridging of traffic.

If you do have any bridging code enabled, however, then this is actually a terrible suggestion.  :)


-----Original Message-----
From: owner-freebsd-net at freebsd.org [mailto:owner-freebsd-net at freebsd.org] On Behalf Of Karl Pielorz
Sent: Tuesday, July 29, 2014 8:02 AM
To: freebsd-net at FreeBSD.org
Subject: FreeBSD 10.0-R connected to Cisco switch (in 'trunk' mode with native VLAN) - doesn't work?


Hi,

I've got a Cisco 3750X switch a colleague is setting up. We've got this 
configured - but it doesn't seem to talk nicely to our FBSD 10.0-R box, 
looks like some kind of VLAN issue (but shouldn't be).


Switch side - the port is configured with:

 switchport trunk encapsulation dot1q
 switchport trunk native vlan 2000
 switchport trunk allowed vlan 2000,2200-2300
 switchport mode trunk


>From what I understand this tells the Cisco to present all the 'allowed' 
VLAN's to the port, and that untagged traffic traversing the port should be 
sent/received as VLAN 2000?

So, we connect our BSD box and do:

   ifconfig bge0 inet 192.168.100.10 netmask 255.255.255.0

But we can't ping another host connected on the network, on '192.168.100.1'.

The above ifconfig uses no VLAN spec, but that should be covered by the 
'trunk native vlan'?


The only way we can fix this - is to take the system 'as-is' and change the 
Cisco port to:

   switchport mode access
   switchport access vlan 2000

This sets the port to be 1 VLAN only, and sets that VLAN to VLAN 2000 - so 
traffic traversing the port will be untagged, but carried as part of VLAN 
2000.

I've been told in theory the bottom config should be the 'same' as the 
previous one (i.e. untagged traffic is treated as VLAN 2000).

But with the top config - the BSD box can't connect anywhere, with the 
bottom config (with the BSD box setup the same) - it can.


Presuming someone here has used Cisco kit with FreeBSD - can anyone see why 
the top config doesn't work? - The guy setting up the switches says he 
always uses the top config - and hasn't had an issue with it, but this 
obviously doesn't work with our FreeBSD boxes.

I would say we'd try it with a different O/S but at the moment, all the kit 
on 'our' side is FreeBSD based...


Cheers,

-Karl



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