Hello,
Just a random thought, what I would check if I were you.
Does your ISP have a limit how many simultaneous IP’s or MAC-addresses they provide address with DHCP to one customer?
If they have, then ISP device port will keep record what’s connected up till the customer leading port goes down and then all is cleared.
Normally this kind of thing doesn’t bother customers which connect their router directly to ISP-device.
But if you have your own ethernet-switch (L2-device) between ISP-device and your router, simply switching router does not clear MAC-table from ISP-device as the link between your switch and ISP-device was not dropped.
If this is the issue, you need to up/down port towards ISP either from managed switch, reconnect ISP-leading cable momentarily or just reboot the switch. Then ISP-device clears MAC-address cache and lets you new IP-address.
This what I described above is a same kind of ISP-devices feature which that is being used enterprise-class switches and for example Cisco IOS switches is implemented:
switch(config-if)# switchport port-security
switch(config-if)# switchport port-security maximum 10
switch(config-if)# switchport port-security violation restrict
Once this is in place, which only limits maximum mac addresses it’s common to also add DAI ( Dynamic Address Inspection) feature, which prevent’s iP-spoofing and requires client IP-addresses to be given by DHCP.
HP has same features by name ARP Protection. And many other vendors have had these available decades also. But these are not on by default and are configured explicitly, which been happening long time increasingly and are now very common.
Thus if you have a switch between your router and ISP-device, clear cache any means written above. If you don’t have a switch between router and ISP-device and can test that the new router get’s and IP when it’s connected local lan of the old router, then you know it’s not with the new device but very likely something with the ISP-side and not with the new router.
There isn’t any real means observing from that ISP-device or enterprise-switch client side ethernet connection what kind of features have been configured. But it’s good to know that those devices can limit and do many network side protecting things most people outside such devices managing aren’t often aware.
So this was just thing that came to my mind what could perhaps cause issues. It could well be that it isn’t if you don’t have switch between and then with a simple test, connect that new thing behind old router, you should be quite easy rule out which side problem lies.
Cheers,
riku
