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Now, our next section here, we'll talk
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and why it is important to have this as a
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Now, in OSPF or BGP,
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the router ID value is used to determine
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In the case of OSPF, we'll see
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This is the identifying value that we
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to use as an input to the SPF algorithm.
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Now, in BGP, the router ID is used
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when we're dealing with route
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But in the case of EIGRP, there's
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And sometimes, it's a little bit of more
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So, the EIGRP router ID is only
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as a loop prevention mechanism to make
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does not get learned back
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and then installed in the topology,
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Now, the idea behind this is that if
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has a lower adminsitrative distance than
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then, we could potentially cause a loop.
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Now really, this case would only
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the external EIGRP distance
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because with the value of 170, it's
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But regardless, EIGRP is still gonna
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So, when we look at the topology
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so for example on switch 1,
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it says, "This is a connected route,
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and we are redistributing
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If we look in the EIGRP
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it says that "This is an external route.
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It came from redistribute connected."
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The minimum bandwidth is 1
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The delay is 10 microseconds.
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Then, the originating router is
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So, it means that this is my router ID
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Now, what this is going to prevent
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is the case where...
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switch 1 advertises this route to 3,
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it goes from 3 to 1, from 1 to 6,
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With internal EIGRP routes,
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because the diffusing update
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are always going to prevent the
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a larger metric value than
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But in the case of external routing
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about the original loop prevention
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whether it's coming from
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when we send the route into EIGRP.
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So, EIGRP is adding this addtional error check
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that has my router ID in the external field,
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Now normally, this case is fine,
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but we could run into a problem if we
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which means that they will not accept
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And it's kind of a difficult
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if you didn't already know that
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So, if we were to look at let's say switch 2,
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and look at what switch 2 says about...
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the route...
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to 7.7.7.7.
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So, we know about this as
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If we look at the topology,
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it says it was originated
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Now, under the EIGRP process,
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and let me remove my previous
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I'm gonna set my router ID
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So essentially, switch 1 and switch 2,
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which means that I will not be able to
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So now, when we look at the
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we see, the route is no longer there.
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If we look in the routing table,
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we don't have the route
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But our adjacent neighbors,
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and look for this prefix.
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Pretty much everyone else in the
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Now, this is a fairly simple case to prevent.
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You would just need to make sure that no
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Or if they did have duplicate addressing,
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like in the case of some sort
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then, we would wanna make sure that
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So, as a general rule, it is a good idea
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the OSPF router ID, the BGP router ID, and the
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The MPLS LDP router ID.
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So, there's specific reasons that
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that are dependent on
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So, we'll see when we get into the
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If two routers that are in the same
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they will withdraw each
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If we have duplicate addresses,
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then we can have separate problems depending
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But we'll take a look at that
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but the point of this here for EIGRP,
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is that everyone has to
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Otherwise, they will not accept
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So, either make sure that all
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or under the process here, just
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