Blinds are 2k/4K, Post flop first to speak goes all in with 3k.
Can the player after him just call? Or he needs to put at least 4K which is the Bb?
What if, pre flop, the Bb have less than the Bb? The answer remains the same?
Hi Mateus. You ask re post-flop and pre-flop The answers are different.
FIRST CASE, Post-FlopThe answer is a long-standing conventional rule, probably best described in RRoP. Your answer depends in large part on whether the stakes of the game are limit or no-limit.
In no-limit there is no such thing as "completing" the bet to 4k. Every bet in no-limit (and pot limit) is considered a complete bet. You can find this rule in RRoP Version 11, Section 14 (No-Limit and Pot Limit), No-Limit Rules Paragraph 2:
....At all other times, when someone goes all-in for less than the minimum bet, a player has the option of just calling the all-in amount. If a player goes all-in for an amount that is less than the minimum bet, a player who wishes to raise must raise at least the amount of the minimum bet. For example, if the minimum bet is $100, and a player goes all-in on the flop for $20, a player may fold, call $20, or raise to at least a total of $120. and also Paragraph 5:
5. “Completing the bet” is a limit poker wager type only, and not used at big-bet poker.See the entire RRoP here:
http://www.homepokertourney.com/roberts-rules-of-poker.htm#SECTION_14_-_NO_LIMIT_AND_POT-LIMITIf you are playing limit, then it's handled a bit differently. See RRoP, Section 3 General Rules, Betting and Raising, Paragraph 7:
...A player... facing an all-in wager of less than half a bet, may fold, call, or complete the wager. An all-in wager of a half a bet or more is treated as a full bet, and a player may fold, call, or make a full raise. (An example of a full raise on a $20 betting round is raising a $15 all-in bet to $35.)...So, in your case the minimum bet is 4k, and the short all-in of 3k amounts to more than 50% of the minimum, so it is considered a complete bet even in limit. The next player can either smooth call the 3k or make a full minimum raise of 4k for a total of 7k.
SECOND question: pre-flop. Everyone with chips must put in at least the BB, even if one or more of the blinds is all-in for less.
Thanks for the great questions. BTW, this forum has a sticky thread that is focused on nothing but min-bets, re-opening the bet, etc. etc. which are frequent questions, you might find that thread useful too:
http://www.pokertda.com/forum/index.php?topic=823.0