Using BPF: (1) AIX 4.x's version of BPF is undocumented and somewhat unstandard; the current BPF support code includes changes that should work around that; it appears to compile and work on at least one AIX 4.3.3 machine. Note that the BPF driver and the "/dev/bpf" devices might not exist on your machine; AIX's tcpdump loads the driver and creates the devices if they don't already exist. Our libpcap should do the same, and the configure script should detect that it's on an AIX system and choose BPF even if the devices aren't there. Also note that tcpdump _binary_ compiled on AIX 4 may have a problem doing the initial loading of the BPF driver if copied to AIX 5 and run there (GH #52). tcpdump binary natively compiled on AIX 5 should not have this issue. (2) If libpcap doesn't compile on your machine when configured to use BPF, or if the workarounds fail to make it work correctly, you should send to tcpdump-workers@lists.tcpdump.org a detailed bug report (if the compile fails, send us the compile error messages; if it compiles but fails to work correctly, send us as detailed as possible a description of the symptoms, including indications of the network link-layer type being wrong or time stamps being wrong). If you fix the problems yourself, please submit a patch by forking the branch at https://github.com/the-tcpdump-group/libpcap/issues and issuing a pull request, so we can incorporate the fixes into the next release. If you don't fix the problems yourself, you can, as a workaround, make libpcap use DLPI instead of BPF. This can be done by specifying the flag: --with-pcap=dlpi to the "configure" script for libpcap. If you use DLPI: (1) It is a good idea to have the latest version of the DLPI driver on your system, since certain versions may be buggy and cause your AIX system to crash. DLPI is included in the fileset bos.rte.tty. I found that the DLPI driver that came with AIX 4.3.2 was buggy, and had to upgrade to bos.rte.tty 4.3.2.4: lslpp -l bos.rte.tty bos.rte.tty 4.3.2.4 COMMITTED Base TTY Support and Commands Updates for AIX filesets can be obtained from: ftp://service.software.ibm.com/aix/fixes/ These updates can be installed with the smit program. (2) After compiling libpcap, you need to make sure that the DLPI driver is loaded. Type: strload -q -d dlpi If the result is: dlpi: yes then the DLPI driver is loaded correctly. If it is: dlpi: no Then you need to type: strload -f /etc/dlpi.conf Check again with strload -q -d dlpi that the dlpi driver is loaded. Alternatively, you can uncomment the lines for DLPI in /etc/pse.conf and reboot the machine; this way DLPI will always be loaded when you boot your system. (3) There appears to be a problem in the DLPI code in some versions of AIX, causing a warning about DL_PROMISC_MULTI failing; this might be responsible for DLPI not being able to capture outgoing packets.