I recently upgraded to Comcast gigabit internet and bought a RB960PGS to replace my previous router that couldn’t handle gigabit speeds. My modem has a 2.5gbps port so I bought a S+RJ10 to connect it to the RB960PGS. I can’t get an IP from Comcast (via DHCP) using the SFP port. The modem light indicates 2.5g connection and the S+RJ10 says it’s linked at 2.5g. I’ve tried disabling the firewall & making sure the SFP port is assigned to WAN and isn’t on the bridge interface. Any ideas?

That device has an sfp port, not sfp+, so you will never get more than 1Gbps on that device. You should really look into at least a 4011 for the Comcast gigabit service.

As for not getting an address, is the DHCP client assigned to the sfp port?

Wow, I can’t believe I missed that it’s only SFP. The dhcp-client was set to use the sfp port. I’ll try a 4011.