I don't know any thing about VM and very little about IP. However I can share one OSA card with multiple LPARS each with its own IP address and possibly a VIPA address. All IP addresses are in the same network, and all have the same physical MAC address of the OSA card.
Craig -----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of David Boyes Sent: Thursday, March 24, 2005 3:55 PM To: [email protected] Subject: Re: Duplicate MAC Addresses > [...] Check out the virtual MAC addresses on the > (edited) response from CP QUERY VSWITCH INTRANET DETAILS, from two > different z/VM systems on two different processors: > In the world of TCP/IP is it "legal" to have two MAC addresses be the > same? Particularly on the same subnet? Makes no difference whether it's IP or some other protocol. MACs are either unique within a vendor (you don't have to worry because the vendor does not reuse MACs), or a user-administered MAC environment (where it's your problem to ensure uniqueness). In either case, MACs must be unique within a layer 2 collision domain. > For these two servers on this particular day, we -can- use TCP/IP to > access the server. But as you know, just because something works (or > works sometimes) doesn't make it "the right thing to do". We > can solve > this by including a unique MACID operand in the directory entry. But > that's a change to 100 or so servers so I'd rather not have > to make that > change if not necessary. This is basically a user-administrated MAC environment. Did you set a unique MACPREFIX in SYSTEM CONFIG? The virtual MAC set in the VSWITCH is made up of two parts: the system MACPREFIX from SYSTEM CONFIG and the MACID on the adapter -- 3 bytes each. The MACPREFIX *must* be unique for ALL VM systems. The MACID will be unique *within* the individual VM image. The combination of the two will be unique across the board. When you set the MACPREFIX, be sure not to use any of the assigned vendor-specific prefixes in the RFCs; if you do, you may get an overlap from common manufacturer cards (esp 3Com and Linksys cards that run very high volume production and recycle MAC prefixes). ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
