If you are a carrier and hold a common carrier authority from the FMCSA, you DO NOT require a broker's license if you are brokering freight in lanes that you are permitted to serve under your common carrier authority.
If you are a carrier and hold a contract carrier authority, you must hold a Motor Carrier Property Broker license.
A MCPB can choose to either have in place a Surety Bond for $10,000, or a trust account where the financial institution guarantees $10,000. The major differemce is that in the event of a shipper defaulting on payment to the broker, the broker is on the hook under the Surety Bond, but off the hook on the Trust Account (as no trust is created due to the non-payment by the shipper)