This isn't the same situation Bill is asking about. In your situation, you have one physical card with multiple IP addresses. That's very frequently done, and works just fine. If there were two cards with the same MAC address on the same physical segment, things would get ugly pretty fast.
Mark Post -----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of Craig Kittendorf Sent: Thursday, March 24, 2005 5:40 PM To: [email protected] Subject: Re: Duplicate MAC Addresses 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 ---------------------------------------------------------------------- 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
