Which two statements about the IS -IS routing protocol are true?（）

• A、IS - IS is capable of supporting IPv4 and IPv6.
• B、IS - IS is only capable of supporting IPv4 and CLNS.
• C、IS - IS routers use ES - IS hellos (ESH) to establish and to maintain neighbor relationships.
• D、IS - IS routers run the Bellman - Ford algorithm against their LSDBs to pick the best paths.
• E、Level 1 routers learn about paths within the area of which they are a part.
• F、Level 2 routers learn about paths both within areas and between areas.