Within the Red Hat certification program, the RHCA is considered the most complete (and grueling) certification among the seven major Red Hat certifications. In fact, some equate the prestige of the RHCA to that of the Microsoft Certified Master and possibly the CCIE.
A plumbing fixture like a sink can not function properly without a sink vent. When a drain pipe drains it creates a negative pressure in the sink drain; the negative pressure will pull the water out of the p-trap of the sink that's draining and sewer gases can enter your home if a sink vent is not installed.
The air vent pipe is clogged. A sewer tape ran down the air vent line (usually on the roof) may unclog the line. 3. The vent line system is to far away from you toilet and is improperly located. If the gurgle is under a sink (kitchen or bathroom) they make a vent that can be installed under the sink. This vent has a baffle to prohibit sewer gas from coming into your house. The baffle opens to allow air into the drain line to release the vacuum.