Theoretically I have solved the problem. Captive portal works on the bridged interface ETH02. The major problem is that the whole configuration is extremely unstable. First I thought the machine ran out of memory but i could rule that out after I had installed another 128 megs of RAM.
System: 466MHz CPU, 384 MB RAM, 1GB CF Sandisk Ultra II, 3 Ethernet cards
– Subnets 192.168.0.0/24 and 192.168.10.0/24 on ETH1 and ETH2 bridged
– Created QoS classes to shape inbound and outbound traffic on both interfaces. All rules affect forwarding between BRIDGE00 and ETH00 or vice versa.
– Bound the QoS rules to traffic to/from particular IP ranges in the classifier
– Added the classes for outbound traffic to eth0, for inbound traffic to the bridge
– Added some firewall rules allowing only particular protocols from the 192.168.10.0/24 subnet, dropping all others.
– Enabled Captive portal on bridged interface ETH02
– Enabled DHCP
Symptoms: This configuration runs fine for some minutes. But then performance drops significantly. Authorization via the Captive Portal works only one or two times, then no more connection to the ZeroBox can be established.
As I mentioned before, i first blamed the lack of memory for that but after upgrading to 384mb the problem still remained. more than 128 mb of ram were always free.
If somebody has an idea of what could be wrong here please let me know.