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I have given the following network diagram and been told that,

Since EIGRP has a better (lower) administrative distance than OSPF, the router on the far left will use the EIGRP path and publish only the EIGRP path to the destination network in its routing table.

Cisco Systems, Inc

Question: Why does EIGRP have a better (lower) administrative distance than OSPF?

Image courtesy: Cisco Systems, Inc

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That is because Cisco determines the AD used by its devices, and EIGRP is a Cisco protocol, so Cisco decided to make EIGRP have a lower AD than other protocols.

Each vendor determines the relative reliability of protocols for its equipment; there is no outside standard for this. Some vendors may not even have an AD equivalent.

According to Cisco default distance value table,

| Route Source          | Default Distance Values   |
|---------------------  |-------------------------  |
| Connected interface   | 0                         |
| Static route          | 1                         |
| EIGRP summary route   | 5                         |
| eBGP                  | 20                        |
| Internal EIGRP**      | 90                        |
| IGRP                  | 100                       |
| OSPF**                | 110                       |
| .............         | ...                       |
  • If possible can you please add a resource/link for further reading? – muhammad Mar 6 '18 at 22:04
  • 1
    Simply search for cisco administrative distance, and you will get things like, What Is Administrative Distance?. As I said, there is no standard. Cisco created Administrative Distance. Other vendors may call it something else (assuming they have something similar). AD is local to a single device, so there is no interoperability requirement. – Ron Maupin Mar 6 '18 at 22:08

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