download

Chapter 7You have to use the tso4 and tso6 options for offloading TCPv4 andTCPv6 segmentations, respectively, as some cards do not support tso forboth IPv4 and IPv6. You can also use these options when you do not wantto enable offloading for a certain protocol stack.If your hardware supports it, you can also offload VLAN tagging to your networkinterface card, if your physical interface is associated with a vlan(4) interface. Toenable hardware VLAN tagging, you may use the following command:# ifconfig bge0 vlanhwtagThis enables VLAN tagging on the physical interface-level. To disable hardwarebasedVLAN tagging, you may use the following command:# ifconfig bge0 –vlanhwtagPromiscuous ModeBy enabling the promiscuous mode, interface does not filter incoming Ethernetframes based on the destination MAC address. It actually passes all incoming trafficto the upper layer in the TCP/IP stack, regardless of the destination address in layer2and layer3 headers.This feature is especially useful while wiretapping on a network interface. Certainsoftware such as tcpdump, enable this mode on the network interface to allow us tosee the passing traffic on the interface. For example, while running tcpdump(1) onxl0 interface, you may see the interface status, which looks like this:# ifconfig xl0xl0: flags=8843 metric0 mtu 1500options=9capabilities=49ether 00:01:02:ae:13:57inet 192.168.14.1 netmask 0xffffff00 broadcast 192.168.14.255media: Ethernet autoselect (100baseTX )status: activeThere are certain cases where you want to manually disable the promiscuous modeon a physical interface. In this case, you may use the following command:# ifconfig xl0 -promisc[ 115 ]