Which Two Statements About IS-IS Are Correct? (Choose Two

Multiple Choice

Which two statements about IS-IS are correct? (Choose two.)

A) Level 1 intermediate systems exchange routing information with Level 1 intermediate systems on other IS-IS areas.
B) An IS-IS router sets the attached bit in the PDUs it sends to a Level 1 area to indicate that it is a backbone router.
C) A Level 1 router can only form adjacencies with other Level 1 routers.
D) Level 2 routers can form adjacencies with either Level 1 or Level 2 routers.