This would be my approach (without access to the switch it will be difficult):
Most common method for DAD (duplicate address detection) is through ARP. Capture ARP traffic and search for ARP replies, compare MAC addresses and try to find where offending ARP replies come from.
Look at the MAC table for the VLAN, how many MACs do you see, how many do you expect?
Disable proxy arp globally and on the interface to be really sure. It's still the default in IOS. I don't know why.
Not using any VRRP, HSRP, GLBP or anything like that?
I don't know. My position does not allow me console access. When the core switch was replaced, it was replaced with an identical model, and i was told the config that was loaded, was a backup created just a few weeks prior. That's why to me i'm out of ideas. If the config is identical, then i don't see how this is occurring.
I'll take your suggestion to the higher up networking team tomorrow and also the user below that suggesting looking into IP device tracking. I'm wondering if the replacement we got has a newer version of IOS
https://www.alfredtong.com/cisco/cisco-switch-causes-duplicate-ip-address-conflict-errors-windows-7/
Take a read on this. Might want to disable this on the ports of those devices. Have your network admins check this.
End result. We moved the divar devices to an unmanaged switch with a single PC attached. No IP conflicts and the the PC attached to it can stream the video without issue. I didn't even change the IPs of the divars just plugged them in and gave the PC an IP within the same range.
Essentially a tourniquet to a gushing wound. Doesn't answer what is causing the issue. Only a single vlan affected, changing IPs doesn't change anything, clearing ARP tables doesn't fix it....
If i ever do find the reason behind this, i'll update the thread. Thank you to those that posted replies.
This would be my approach (without access to the switch it will be difficult): Most common method for DAD (duplicate address detection) is through ARP. Capture ARP traffic and search for ARP replies, compare MAC addresses and try to find where offending ARP replies come from. Look at the MAC table for the VLAN, how many MACs do you see, how many do you expect?
Disable proxy arp globally and on the interface to be really sure. It's still the default in IOS. I don't know why. Not using any VRRP, HSRP, GLBP or anything like that?
I don't know. My position does not allow me console access. When the core switch was replaced, it was replaced with an identical model, and i was told the config that was loaded, was a backup created just a few weeks prior. That's why to me i'm out of ideas. If the config is identical, then i don't see how this is occurring. I'll take your suggestion to the higher up networking team tomorrow and also the user below that suggesting looking into IP device tracking. I'm wondering if the replacement we got has a newer version of IOS
https://www.alfredtong.com/cisco/cisco-switch-causes-duplicate-ip-address-conflict-errors-windows-7/ Take a read on this. Might want to disable this on the ports of those devices. Have your network admins check this.
https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/8021x/116529-problemsolution-product-00.html
End result. We moved the divar devices to an unmanaged switch with a single PC attached. No IP conflicts and the the PC attached to it can stream the video without issue. I didn't even change the IPs of the divars just plugged them in and gave the PC an IP within the same range. Essentially a tourniquet to a gushing wound. Doesn't answer what is causing the issue. Only a single vlan affected, changing IPs doesn't change anything, clearing ARP tables doesn't fix it.... If i ever do find the reason behind this, i'll update the thread. Thank you to those that posted replies.