LEICHTER-JERRY@YALE.ARPA.UUCP (03/04/87)
In a recent message, I said some things about this mode that were, at best, confusing - mainly because I was confused. I've spent some time now staring at the driver code, and I THINK I've got it figured out: You can turn on "accept all multicast addresses" on an inactive protocol, so you can't share a protocol with an "accept all multicast addresses" user. The restriction is thus the same as for promiscuous mode, except that PHY_IO is NOT required. If any unit anywhere has specified this mode, the hardware is set to accept all multicast addresses. When an incoming packet for a protocol arrives, the driver effectively must do some filtering, since the packet may have been destined for a multicast address enabled for a different protocol; so the driver has the ability al- ready. All that happens when "accept all multicast addresses" is enabled is that the driver will potentially have more work to do, as there could be a lot more multicast packets received that it will have to process and discard. (On most Ethernets, this is probably not a major issue.) Enabling "accept all multicast addresses" mode has no DIRECT effect on the number of multicast addresses that may be specified. Each unit continues to be limited to 10, and the total number across all units continues to be limited to 10. A unit with this mode enabled may still have a multicast address list - it will be ignored as long as the unit is enabled for "accept all multicast addresses", however. The driver will NOT fall back to this mode automatically if an attempt to enable more than 10 multicast addresses is made; it will return an error instead. The XQDRIVER is complex enough that I wouldn't want to be held to the above as gospel truth. If in doubt, try it! - and report back here. -- Jerry -------