Alan Altmark frequently makes reference to what he calls the "Golden IP Routing Rule:" "Two hosts in the same subnet can hear each other's broadcasts." Ask your networking folks if they think the setup they've forced on you will allow the SLES7 host to hear the broadcasts of the systems out in "the world" part of your diagram. To give them further food for thought, replace "z/VM 4.2 OSD channel" with "router" and the same for "z/VM 4.2 hipersocket."
Note also that HiperSocket guest LANS don't support broadcast. QDIO guest LANS do. Mark Post -----Original Message----- From: Bishop, Peter G [mailto:[EMAIL PROTECTED] Sent: Sunday, March 16, 2003 10:34 PM To: [EMAIL PROTECTED] Subject: routing hipersocket guest LANs without a separate guest LAN subne t - impossible? Hi, There have been some recent threads similar to this, but they haven't cleared up this question...we've been racking our brains here and haven't yet determined that this is impossible, but we suspect it may be. Here's a picture +-------------+ +------------+ A +----------------------+ | "the world" +--------+ switch +--------------+ z/VM 4.2 OSD channel | x.y.z.225 +-------------+ +------------+ +----------+-----------+ x.y.z.254 | B| | +----------------------+ + z/VM 4.2 hipersocket | x.y.z.228 +----------+-----------+ | B| | +----------+-----------+ + SLES7, 8 hipersocket | x.y.z.226 +----------------------+ What we'd like to know is: can this be done on the same subnet? Until we can convince the network blokes that we need a routable subnet, we're stuck trying to do it on the same subnet, netmask of 255.255.255.192 if that matters. All the docs we've read (including the helpful "z/VM Guest LAN Implementation for Penguin Colonies" by John von Wolfersdorf at the WSC) show the real LAN on a different subnet than the guest LAN, respectively links A and B above. In fact, the doc I just mentioned has two guest LAN subnets, both different and both on a different network than the real LAN. No matter what routing entries I've tried, none seem to be able to route the traffic into the guest LAN from the real LAN, and back out again. I can get to and from the .228 address OK, but I'm told that's because the OSA at .225 is using its primary router function to pass unknown packets on to wherever it can. No such joy with the .226 address as the hipersocket device seems not to have this feature. I'm writing to the network blokes, but thought in the meantime I'd grasp at any straw around to see if we could get it working while we wait for them to provide the optimum. The value of x.y.z in each case above is the same, only the final octet is different for each node. For those wondering why the 228 and 226 aren't reversed, the 226 came first while I was installing it with a CTC connection to get started...it's easily-enough changed anyway, eh? It doesn't seem to matter if SLES7 or SLES8 are the guest, both fail. If anyone needs more info, like output from ifconfig/Q LAN/Q NIC/whatever, I've got that.. best regards and thanks in advance for any light you may be able to shed, Peter Bishop GOSD Mainframe EDS Asia-Pacific phone +61 2 9378 0113 email [EMAIL PROTECTED]
