5

OSPF has an administrative distance of 110
EIGRP has an administrative distance of 90
RIP has an administrative distance of 120

But where did 110, 90, and 120 come from?

  • Who or what entity decided the Administrative Distance values for each of these (and all other) protocols?
  • What document or RFC were these values established in?
2

Since AD is only local to a router, not affecting any other router, it would be the router vendors. AD is not sent to any other device; it is only used to determine which route is best in the local router.

Certainly Cisco decided EIGRP should be more trustworthy than the other protocols.

| improve this answer | |
  • But those values are surely not Cisco only. I see the same values on Juniper devices (well, not for EIGRP, I guess). Why would Juniper choose to use the same values? – Eddie Jan 24 '16 at 22:50
  • 1
    I think Juniper chose the values because they work and were proven by Cisco, and the Juniper founders jumped ship from Cisco. It would certainly help Juniper to be consistent with Cisco when selling to Cisco customers. I think it's one of those things that just became a de facto standard because it worked. You could certainly have a router with different set of values or something completely different to determine which protocol is more trustworthy Things like this only matter within the single device, so they don't matter to the rest of the network, and they don't need to be consistent. – Ron Maupin Jan 24 '16 at 23:17
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    Cisco is the "800 pound gorilla" and every other manufacturer knows they need to be compatible with them if they are to succeed. HP uses the same values, btw. – Ron Trunk Jan 25 '16 at 1:03
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    To piggy back off the, "the values are locally significant" point, Juniper's "preference values" (admin distance in Juniper land), are completely different from Cisco. juniper.net/documentation/en_US/junos15.1/topics/reference/… – Jordan Head Jan 25 '16 at 12:04

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