OSPF and IS-IS: Choosing an IGP for Large-Scale Networks

4.5. Media Types

The preceding discussion on DRs and DISs makes it clear that both OSPF and IS-IS behave differently for different physical media. Understanding these differences is important not only for correctly designing your networks but also for troubleshooting problems on your network.

4.5.1. OSPF Network Types

OSPF classifies all interfaces, physical or logical, into one of five network types:

• Broadcast networks

• Point-to-point networks

• Nonbroadcast multi-access (NBMA) networks

• Point-to-multipoint networks

• Virtual links

Broadcast networks might be more accurately named broadcast multi-access networks. More than two devices can connect to the network, and packets sent by one device can be seen by all connected devices. These days, broadcast ...