USSR/Red China. Contrary to popular opinion, by far, the bulk of the AK47s, grenades, trucks, PT76/T54 tanks, MiG17 jets (J5 series) were CHICOM (Communist Chinese). The Soviets quit sending North Vietnam MiG17s and concentrated solely on MiG21s; the Red Chinese supplied the only MiG19s (J6 versions) to the North Viet AF.
So it looked like this: Only USSR supplied the MiG21 & only Red China supplied the MiG19 to North Vietnam. But both nations supplied Hanoi with the MiG17. Soviets supplied North w/ground defense weapons such as SAMs/radar, etc.
Communist North Vietnam was supported by the Soviet Union and, later, by the People's Republic of China against the Capitalist US-supported South Vietnam.
Hours after Japan's surrender in World War II, Vietnamese communist Ho Chi Minh declares the independence of Vietnam from France.
North Vietnam was communist, supported by Russia, China, and Cuba.
Warsaw Pact nations, the USSR, and Red China supplied equipment to North VN. Obviously they supported North Vietnam. Neutral nations such as France, Great Britain, Canada, Central America, South America, etc. etc. etc. may have expressed "favor" for the North, but they remained neutral during the war.
Vietnamese Communists (Viet Cong) vs. the South Vietnamese Army and the US. Many other countries supported but the main ones are above
The Soviet Union supported the Democratic Republic of Vietnam (North Vietnam) under Ho Chi Minh.
There are no nations that have acted out against the US in order to have supported North Korea in any past conflicts, as of 2013. While many nations such as Soviet nations and China have supported North Korea at times, they did so without malice toward the United States.
The communist superpowers supported the north with war material. The US supported the south with men & material. Reason: Cold War.
The Vietnam war is also called the Second Indochina War. The war was fought by between North Vietnam who were supported by China and Soviet Union and South Vietnam which was supported by the United States.
The Socialist Democratic - or Communist Party dominated North Vietnam politics, and continues to do so today over the unified Vietnam.
Asia
Both nations were created in 1954/55. North defeated the South on 30 April '75; 1975 one nation/Vietnam.