MX85 swap failed

[Schiller]

In one of my branch offices, there is an MX84. I have decided to replace it with an MX85 to improve the throughput. I set up a temporary network on my dashboard for pre-configuring the MX85. When I removed the MX85 from the temp network and add it to the branch office’s network, my MX85 failed to connect to the Internet. Do anyone have an idea why it fail to connect to the Internet? 

Thank you in advance. 

[Ryan_Miles]

Does the current MX84 use a static IP on the WAN interface? If yes did you configure the same IP on the MX85?

[Schiller]

No, I have a dynamic IP on my WAN port. And of course this port is set to dynamic. 

Thank you for your response. 

[GreenMan]

Following on from Ryan's question - if you did re-use the static IP, did you take steps to refresh the ARP cache on whatever L3 device is upstream, to reflect the changed MAC address?

[Schiller]

My MX is connected to the ISP modem. I asked my Internet provider to do that. 

Thank you for your response. 

[IT_Magician]

After confirming IP addresses is correct, I would also get your ISP on the phone. Sometimes they need to clear the ARP table on their side to make sure their modem properly bridges with your device.

[Schiller]

Yes, I did 

thank you.