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Here’s an example to demonstrate this in more detail.

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If the San Jose router in this topology is advertising network 10.0.0.0/8

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to the San Francisco router using RIP version 2

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the San Francisco router will deem that the believability factor

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or administrative distance of that route is 120.

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If the same network was advertised by the New York router using EIGRP

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the San Francisco router will allocate that route

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a believability or admin distance of 90.

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the San Francisco router will does install this route received

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via EIGRP from the New York router into its local routing table

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and traffic received going to an IP address of 10.1.1.1 for example

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will be routed to the New York router and not to the San Jose router.

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The same network is received from the different neighboring devices

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via different routing protocols

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and administrative distance was used in this example as a tie breaker.

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The more believable routing protocol is EIGRP

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the RIP route is not installed

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in the local routing table on the San Francisco router.

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The EIGRP route is installed and traffic is routed

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to New York to get to host in this network.

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now the San Francisco router still has the RIP route

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in its RIP database so if the EIGRP route was no longer available

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the RIP route will be installed in the routing table

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and San Francisco would route the traffic to San Jose

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to get to host devices in network 10.0.0.0

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in other words, if this link went down for some reason

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and there was no connectivity between San Francisco

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and New York traffic will then be sent to San Jose

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but if the link came back again the EIGRP route

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that’s then advertised would supersede the RIP route

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and traffic will now be routed to New York.

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So New York is the first choice

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and will be used if that neighbor is available

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and San Jose is the 2nd choice to get to the same network.