Which of the following is used by an IS-IS router to detect other IS-IS neighbor routers and to form
adjacencies?
A.
ESH
B.
ISH
C.
IIH
D.
PSNP
E.
CSNP
Explanation:
ISIS actually features three different hello types
An ES Hello (ESH) is send by all End Systems, and all IS devices listen for this Hello
An IS Hello (ISH) announces the presence of an IS – An IS Hello is sent by all IS devices, and End
Systems listen for these hellos Finally, an IS-to-IS Hello (IIH) is used by an IS to discover other ISes
and to form adjacencies with them A router will send an IIH to another router on the link to form or
maintain an adjacency, but it will still send an ISH as well in case there are end systems located on
that segment