broadcast on VLAN trunk
 

I have noticed centos 6 with VLAN trunk, for example,

eth0: 10.0.0.1 (untagged)
eth0.10: 10.0.10.1
eth0.20: 10.0.20.1

broadcast packet on VLAN10 is observed both on eth0.10 and eth0(untagged). (confirmed with tcpdump)
Old linux like centos5 or fedora7 or so,
broadcast packet on VLAN10 was received only on
eth0.10, not eth0.

I don't know whether this is a bug or not, but
I prefer old behavior on my system.
Is there any way to change the behavior to old one?

Thanks,

what are you actually seeing on the untagged interface? As it is the underlying channel it clearly WILL see the traffic, but will have an 802.1q tag on it. It's still legitimate ethernet traffic though. This might be a change in tcpdump, not the taging logic itself.

It is most definitely not correct behaviour. Are you doing a tcpdump on the receiving end of the trunk? I assume what you are seeing reported is both a tagged and an untagged copy of the same broadcast?

Is there any chance you've bridged the two vlans via a bridge interface somewhere?