Hi everyone,

I am currently trying to set up a tap interface on my system. I have created a bridge between an ethernet interface and this tap interface using brctl. I set both the ethernet and tap interfaces to 0.0.0.0 and promisc before adding them to the bridge, and set the bridge to an IP of 192.168.10.2.

I then tried to ping the bridge from another box on the 192.168.10.X network. Using tcpdump I am able to see the packets entering both the bridge, and the ethernet interfaces. However, tcpdump shows no packets reaching the tap interface. I need to be able to ping this tap interface from another box on the same interface.

I am mistaken in thinking that the bridge should send the packets to both interfaces? Any help on fixing this porblem would be much appreciated.

Thanks

Do you set tap interface permission?

Hi nini09,

Thanks for your reply.
Yes I have the permissions set correctly. Everyone has read/write permissions to /dev/net/tun.

Edit: I am also running tcpdump as root

How about broadcast packet, such as ARP request? Can tap interface receive broadcast packet?

The tap interface is receiving ARP requests, nini09.

Someone report this kind of the behavior. The bridge is like switch, not hub. The switch only broadcast the broadcast packet, such as ARP request, doesn't broadcast unicast packet. The Hub broadcast every packet.

Hi again nini09,

Do you mean someone has reported this issue on linuxquestions before?

Thanks

Someone get same behavior, broadcast packet is different from unicast.
By default, bridge on Linux is like switch. But if you want to change the behavior, like Hub, a side affect command could make it.
brctl setageing <bridgename> 0

1 members found this post helpful.

Thanks for your help nini09,

I will have another look into that then and see if that fixes my issue.

Hi again nini09,

Just wanted to say thanks for you help! Your command worked perfectly.

Thanks