Which two actions does the engineer take to accomplish this segregation?

A network engineer must segregate three interconnected campus networks using IS-IS routing. A two-layer hierarchy must be used to support large routing domains and to avoid more specific routes from each campus network being advertised to other campus network routers automatically .

Which two actions does the engineer take to accomplish this segregation? (Choose two.)
A . Designate two IS-IS routers as BDR routers at the edge of each campus, and configure one BDR for all Level 1 routers and one BDR for all Level 2 routers.
B . Designate two IS-IS routers from each campus to act as Level 1/Level 2 backbone routers at the edge of each campus network.
C . Assign the same IS-IS NET value for each campus, and configure internal campus routers with Level 1/ Level 2 routing.
D . Utilize different MTU values for each campus network segment. Level 2 backbone routers must utilize a larger MTU size of 9216.
E . Assign a unique IS-IS NET value for each campus, and configure internal campus
routers with Level 1 routing.

Answer: B,E