On Wednesday, 01/28/2004 at 01:06 CET, Franco Mignogna <[EMAIL PROTECTED]> wrote:
> I suspect the problem here is that Gbit OSA uses QDIO mode; according > http://www.redbooks.ibm.com/redbooks/pdfs/sg245948.pdf in QDIO mode an OSA > card answers to ARP request by itself, having IP addresses registered by > the IP stack. In the above redbook the process of ARP takeover is described > (is this what you mean for IP takeover ?). > In the above radbook a reference to spantree exists. I don't know if it > applies to Lucius's problem, and I don't whanto to add confusion, but it ARP takeover and IP takeover are the same thing: Moving the association of an IP address from one adapter to another. It really doesn't matter if it is a VIPA or the base IP address. z/OS can move the base IP address *and* the VIPA between adapters. To the best of my knowledge, Linux doesn't, as it requires cooperation between the IP layer and the device driver that doesn't exist on Linux. The *intent* of VIPA is to insulate the host from IP address changes AND to provide failover. If you put the VIPA in the same subnet as the adapters, then you lose half of the insulating value (hey! it's cold outside!) of the VIPA. When in a different subnet, it is not necessary for the adapters to respond to ARPs for the VIPAs - they just have to add it to their IP filters. But as you suggest, the core of the problem is the gratuitous ARP performed by OSA when it is in QDIO mode. If Linux does not tell the adapter "Hey, don't do that!", then OSA will not register the IP address and will not respond to ARPs for it. Fixing that is relatively easy. To have both adapters running and moving traffic, with transparent failover for all traffic to a single adapter is much harder (requiring that cooperation thing). When Linux can do that, then you can failover same-subnet VIPA the same way. Alan Altmark Sr. Software Engineer IBM z/VM Development
