On Tuesday, 02/17/2009 at 05:06 EST, Shimon Lebowitz <shim...@iname.com> wrote:
> OK, so now we know that in 5.3 VM does *not* register other > addresses with the OSA. So I seem to have a problem if > I want to continue to use the old address (10.1.5.2) to get to VM. > (Hmmm... could I fake-it by defining 10.1.5.2 as a VIPA address? > You say that *does* get registered on the OSA) Yes. If you don't want that stack to be PRIROUTER, then the only way to get to any other HOME address (that isn't connected to that OSA) is to make them VIPAs. > > OSA routing rules don't care what is plugged into them, so, yes, IP (layer > > 3) VSWITCH connections have the same issues. The nice thing about > > ETHERNET VSWITCHes (Layer 2) is that PRIROUTER does not apply. Each guest > > gets the packets it is supposed to get without any worrying about whether > > you're routing into another network though the VSWITCH or not. > > Each guest just "gets its packets"? I tend to be afraid of > "magical explanations" - why would packets get to the VSE > with the "wrong" addressing, just because its a level 2 VSWITCH? In layer 2, there is no IP address registration in the OSA (ARPs are handled by the host) and the only filtering the OSA does is based on MAC address (virtual MACs are registered by CP). So any destination IP address can be used, letting you avoid VIPAs, if desired, and not worry about having to have PRIROUTER to accomplish the same thing with Layer 3. > Also, can I attach VM-TCPIP and z/VSE to an ETHERNET > VSWITCH in z/VM 5.3? z/VM 5.3 TCP/IP does not support layer 2 VSWITCH. > So now it looks like Layer 2 might even be worse? If Unwanted Packets arrive, they must be Dealt With. The only question is what you do with them. Let them clog up the OSA? Or the host? Answer: Neither. Don't put stuff on the LAN that you don't want the OSA to see. Of course, if "gazillion" is really only a few hundred a minute, who cares? The advantages of layer 2 outweigh (IMO) the disadvantages, since those disadvantages can be largely mitigated by slight change in network design. > Since my VM-TCPIP that acts as virtual router for the assorted > VSE machines is now on the network (as seen in the left side > of the picture in my first post), I assume that if it has managed > until now it must be OK with the quantity of traffic. Yes. Though any unwanted broadcast will annoy ALL layer 2 hosts, not just a single stack. > > And it makes packet traces easier to manage due to reduced volume of > > traffic, because if memory serves, yes, all active interfaces will receive > > a copy of a broadcast packet. That means all hosts on the VSWITCH will > > get a copy of the broadcast. > > Sorry, I got confused. What is the "it" that makes traces easier? "It" := Putting the OSAs in their own LAN segment. "It's a Good Thing." Alan Altmark z/VM Development IBM Endicott
