Nothing to worry about.
It has to do with the private 10.x IP given out to modems for diagnostics reasons.
Its transparent so you won't see it in a trace.
To get the IP the modem uses DHCP similar to how your PC/Router uses DHCP to get your public IP.
However, the DHCP client in the modem isn't as fancy(doesn't need to be)as the one in your router/PC so it can't understand everything Cox DHCP server is saying.

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