DIAGNOSIS Yes, normal. This router has a large heatsink and no fan. It dissipates heat through the case.
FIX Ensure proper ventilation. Do not place it on carpet, in a closed cabinet, or under other electronics. Leave at least 4 inches of clear space on all sides, especially the top vent.
IF THAT DIDN'T WORK If it feels excessively hot—too hot to keep your hand on—check the power adapter. Use only the 12V/2.5A adapter it came with. A higher-amperage adapter can cause overheating.
HEADS UP The case is designed to be warm. This is not a defect. Overheating would cause it to reboot or throttle performance, not just feel hot.