OK, your description of the issue was pretty vague.
Based on your last, am I correct in assuming you are not trying to access the MBG but instead have a PC on the voice lan that you want to access the internet using the MBG as the gateway?
If so
DHCP should provide MBG LAN port as Gateway (Option 3)
DHCP should provide MBG LAN port DNS (Option 6)
Or statically assign accordingly
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