snooping 802.1Q frames on a trunk


Just for fun I decided to look at 802.1Q frames between two trunk ports that connect two 3524. What I did is connect the trunk ports via a hub and use Ethereal to watch the traffic.

I was expecting to see frames tagged with 0x8100, but all traffic was standard Etherent tags. Setting the trunk encapsulation to ISL works as expected and all traffic is encapsulated in ISL. At first

I tried both the following configs

interface FastEthernet0/24 switchport trunk encapsulation dot1q switchport trunk allowed vlan 1,98,99,1002-1005 switchport mode trunk

interface FastEthernet0/24 switchport multi vlan 98,99 switchport mode multi

but never see tagged frames

My undertanding of non tagged frames on trunks was that only the Native VLAN frames are untagged.

On both VLANS I created traffic (long ftp session and continous traffic)

What am I missing?



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Capitan Mutanda
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