Users of older Mac's not able to obtain DHCP

[jalderson]

Good afternoon, I have a strange issue at one of my sites.  Occasionally users on older Mac's cannot get on the network.  Their computers connect, but no IP address is assigned and they eventually give themselves the 169. address. I use a Windows laptop and had no issues connecting on the WiFi. I contacted Meraki support, the tech claimed that the machine I was trying to connect from was not seen in his packet capture (he was looking this up via the MAC address of the Macintosh I was connecting from.)  DHCP is handled by a Windows server, and this was tested and functioning properly.  We tried connecting to the guest network which uses the MR33 as the DHCP server, same issue.  I then tried creating a new guest network and the client could connect.  Now the strange part is, if I reboot the MR33 everything will work fine for a few weeks without issue.  Also note there are two MR33's, only one so far seems to have this issue, but I still need to swap the access points to confirm this. Also firmware is up to date.  Any suggestions would be greatly welcomed, thank you for your help,
Jon

[Nash]

Are you able to run a packet capture from one of the Macs that is having problems, when it is having problems?

[jalderson]

Yes the tech ran a capture by Mac address but said he could not see any traffic from the computer I was trying to connect from.

[PhilipDAth]

Any chance of a DHCP conflict, or DHCP giving the machine an IP address assigned to something out?

Often when machines get given a DHCP address they ARP for it to make sure no one else responds.  If no one responds they use it.  If someone else responds they use the 169 style addresses.

[BlakeRichardson]

Hmmm last Friday we had a similar problem, our DHCP on that VLAN was being hosted from a Mac using the server app and suddenly two desktops wouldn't get a DHCP lease and would end up self assigned. My MacBook and another MacBook would get a DHCP lease without any issues.

We rebooted switches, servers to no avail. In the end we migrated the DHCP to another piece of hardware and it worked.... No changes were made to the server or network before it stopped working.

[jalderson]

None that I could see.  When I plugged the Mac's in using a hard wire they got an address just fine.  Also, my laptop, which is Windows based, did not have any issues connecting. Once the access point was rebooted, all was well again, strange.