Overview:
Administrative distance is what is used to select the best path when a router has two different paths to the same destination via two different routing protocols.
Study Notes:
- Most routing protocols are not compatible with other protocols.
- In a network with multiple routing protocols, being able to select the best path between multiple protocols is critical.
- Administrative distance defines the reliability of a routing protocol.
- Each routing protocol is prioritized in order of most to least reliable (believable) with the help of an administrative distance value.
- IPv6 uses the same distances as IPv4.
- Default Administrative Distances:
|
Routing Protocol |
Administrative Distance |
| Connected | 0 |
| Static | 1 |
| BGP (external) | 20 |
| EIGRP | 90 |
| IGRP | 100 |
| OSPF | 110 |
| RIP | 120 |
| BGP (internal) | 200 |
See CCNA 3.3.a: Admin Distance for a full list