Hi Shayne, On 28/02/17 11:10, Shayne Ghere wrote: > I’m reaching out since we just started having problems with users > complaining about getting messages on their Mac’s about a duplicate IP > address on the network. > > When looking in the ARP table of the Cisco Nexus switches, the mac > address of their computer isn’t in there, however the IP address their > machine has is owned by another mac address even though both the > Controller and Prime doesn’t see that machine associated. > > I came across an article that the Arp Cache Timeout on the 6509’s was > 300 seconds, but the Nexus (7K) has bumped it to 1500-1800 seconds > now. That jives with what I’m seeing as the disassociation time of the > original machine, and the duplicate message (within 20-25 minutes). > > The Arp-Cache timeout on the Controller is set for 1800 seconds, and was > configured that way since September 2016 (Cisco WLC 8540) with no problems. > > This problem just cropped up within the past two weeks and is gaining > steam. Out of the 30 or so devices, 38 are Mac’s and the other two are > Windows 10 or Microsoft Surface tablets. > > If anyone else is experiencing these issues, or could point us in the > right direction, I would greatly appreciate it. Our Server/Radius team > is fairly sure it’s not on their end, yet after talking with Cisco, I’m > fairly positive it’s not the Controller/Wireless. Not finger pointing, > just asking for some advice.
Do you have any Apple TVs on your network? Apple devices have a lovely feature called the Bonjour Sleep Proxy that will respond to mDNS queries for a device that is asleep. The visible side effect is what you are seeing, the IP address is owned by another MAC address. What sort of devices are the ones stealing the IP addresses? For us, the solution was to statically (via DHCP) assign IPs to the Apple TVs. Thanks, -- James Andrewartha Network & Projects Engineer Christ Church Grammar School Claremont, Western Australia Ph. (08) 9442 1757 Mob. 0424 160 877 ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss.
