After I printed the Supply IP Tackle in Multicast Packets weblog put up, Erik Auerswald despatched me a number of examples of community units sending IP packets with supply IP handle set to 0.0.0.0:
There’s additionally the notorious case of switches configured with EVPN proxy ARP performance however with out a usable IP handle. These switches ship ARP requests with supply IP handle 0.0.0.0 when making an attempt to validate cached ARP entries, complicated Home windows hosts buying their IP handle through DHCP – ARP requests despatched from IP handle 0.0.0.0 are used early in DHCP handle acquisition course of to permit DHCP purchasers to detect duplicate IPv4 addresses.
The foundation reason behind all these SNAFUs: a community machine means that you can configure IP performance on interfaces with out usable IP addresses. I wouldn’t be shocked if these units use no matter worth is within the “interface IP handle” subject with out checking it’s not zero. Or as Erik concluded in his e-mail:
What I see as problematic is that all the above usually simply works, so distributors don’t have any motivation to discover a clear answer. Typically one thing breaks in surprising methods, and one begins to surprise how something may have labored earlier than.
Even worse, typically distributors publish a data base article telling you methods to configure different vendor’s gear to tolerate their stupidity. Static ARP entries for Microsoft NLB instantly come to thoughts as does this VMware mastepiece.
