RB-750G Ether1-Gateway not working with Morotorola Surfboard

RouterOS General
1

I’ve got an RB-750 that I want to replace with an RB-750G and I can’t get any connectivity between the RB-750G and the Motorola Surfboard cable modem.

First I exported in imported the RB-750’s config into the RB-750G but the RB-750G didn’t seem to be getting a DHCP address from the Motorola Surfboard cable modem on it’s Ether1-Gateway port. I had a link light but no connectivity, the RB-750G wouldn’t even respond to a ping from the internet. Then I tried the RB-750G with the default config (after \system reset) and it still wouldn’t work. Again I had a link light but no connectivity in or out. Next I disabled the RB-750G’s DHCP client on the Ether1-Gateway port and manually configured it for the public IP address that the Surfboard has been giving out via DCHP for years. It’s a dynamic IP address but it never changes even after widespread system wide outages experienced by the cable company. That seems to be our address. Anyway, Even with the IP address manually configured I still couldn’t get any connectivity.

I’m located in South America and the modem/RB-750G in question are in NY. I’m managing all this remotely. When I was testing connectivity I was trying to ping the router from the internet, connect to the router via WinBox from the internet, and by having the local users attempt to access the internet. All of those failed.

Now my guess is the RB-750G and modem are not successfully auto-negotiating the Ethernet port parameters. So I had the user pick up a cross over cable which I’m going to try next with the RB-750G set to 100Mbps and full duplex.

Any ideas about what the problem could be would be greatly appreciated.

Greg

2

The problem was I needed to reset the cable modem. Another thing that was throwing me for a loop was the cable modem gives out the same DHCP address to the original RB-750 even after major power failures and cable company system outages which made me think we always received the same IP address from the modem, but the RB-750G was getting a different IP address I’m assuming because the cable company’s system is seeing a different MAC address from the RB-750G. I’m doing this job remotely and I was pinging from the internet side and expecting a certain IP address to answer.

I did learn that when exporting/importing the config between different boxes such as the RB-750 to RB-750G there are many things in the exported config that are incompatible to be imported, so I ended up exporting specific sections of the setup such as /ip firewall, /queue, /system script, /system scheduler, /ip address, /ip pool. I think in the future I’d do just the bare minimum to get the box accessible via WinBox and then while having access to both boxes via WinBox do the rest of the config section by section.

Greg