Defending against Zergling Rush as TerranDefending against a horde of Zerglings as Terran by barricading the entrance to your base with Barracks, supply depots with addition of marines, bunkers and siege tanks are only a few ways to protect your base from an early attack by zergling swarm.
Defending your Terran base from an imminently incoming zergling rush is not very difficult because a Terran player actually has many options for dealing with this situation.
Some of these options use light units such as marines and supply depots, other solutions will take advantage of a heavy unit such as a Siege Tank in the siege mode. Two or more Hellions behind the supply depots can be used. Four marines in a Bunker can be used just as effectively.
One of the first things that Terran player should do is start walling off the ramp entrance to his base. This is commonly done using a Barracks building and two or more supply depots (depending on the width of the ramp).
The Barracks can then be used to immediately start building marines, which will be able to easily eradicate the zerglings swarming at the ramp as the Marines will be positioned behind the wall and are capable of ranged attack. (Though you always have to wonder how the Marines’ bullets pass through the supply depots and the Barracks so easily without causing any damage at all!)
Once the Terran player has produced at least one Siege Tank, then the zerg player can forget about the rush completely. A Siege Tank will simply devastate swarms of Zerglings or even a more powerful unit such as the Roach. Remember, that a Siege Tank in siege mode will deal splash damage which is deadly to large quantities of non-upgraded zerglings.
Before the Siege Tank can be produced, however, it is important to note that a supply depot is most likely to be targeted during a break-in, since it has less hit points than a Barracks.
As a Terran playing against Zerg, one tactic to be on the look out for is the Baneling Bust which is one of the zerg banelings strategies. Though the baneling bust strategy is commonly thought of as being used to destroy the entire wall barricade, a lot of banelings must be used in order to do that. And more units means more time.
My suggestion for a smart Zerg player is to use math when calculating the baneling bust attack, especially close to the beginning of the game.
Only 5 Banelings are required to bust a supply depot and even possibly cause splash damage to nearby marines. This opening in the wall can be effectively used by the Zerg opponent to let in the swarm of zerglings or, even more dangerously, fastlings.
An even smarter Terran player will keep his SCV right behind the Barracks and Supply Depots, but there is simply not enough time for SCVs to start repairing the Supply Depot when banelings attack. The siege tank in siege mode in a combination with marines or hellions is probably the best way to handle an incoming banelings bust containing no more than 10 banelings.