What is an important difference between OSPF and IS-IS?

What is an important difference between OSPF and IS-IS?
A . OSPF runs directly on IP, while IS-IS runs directly on Ethernet.
B . OSPF is a link state protocol, while IS-IS is a distance vector protocol.
C . OSPF runs directly on Ethernet, while IS-IS runs directly on IP.
D . OSPF is a distance vector protocol, while IS-IS is a link state protocol.

View Answer

Answer: A

Explanation:

OSPF runs directly on IP, while IS-IS runs directly on Ethernet. This means that OSPF uses IP addresses to identify routers and links, while IS-IS uses MAC addresses or other link-layer identifiers. OSPF also requires an IP header for each packet, while IS-IS does not. Both OSPF and IS-IS are link state protocols, which means that they flood information about the network topology to all routers in the same area or domain.

Reference: Ericsson IP Networking – Routing Protocols, Ericsson Router 6000 Series – Ericsson