When there are two or more different routes to the same destination from two different routing protocols, Administrative Distance counts the reliability of a routing protocol. The AD value can range from 0 to 255. A lower AD value is more trusted by an L3 device. Therefore, the best AD value is 0 (lower number is always better) and the worst is 255.
| Route source/Protocol | Default Distance Values |
|---|---|
| Connected interface | 0 |
| Static route | 1 |
| EIGRP summary route | 5 |
| eBGP | 20 |
| Internal EIGRP | 90 |
| IGRP | 100 |
| OSPF | 110 |
| IS-IS | 115 |
| RIP | 120 |
| EGP | 140 |
| ODR | 160 |
| External EIGRP | 170 |
| iBGP | 200 |
| Unknown | 255 |