If you bought your B311-221 from a network carrier (e.g., locked to Vodafone, MTN, or Telstra), it will not accept SIM cards from other providers. To make it truly portable (usable with any local SIM while traveling), it must be unlocked.
Flashing the wrong firmware can brick your router. Before downloading any file, you must identify your exact hardware revision. huawei b311221 firmware portable
Not truly "portable" for use on the go without an AC outlet. If you bought your B311-221 from a network carrier (e