Welcome to the blog in the video we're going to look at why specific Roths were chosen rather than others
network running Cisco routers
so apologies for routers running with ingenius 3.
Let's have a look at Router one and use the Camacho IP ROFFT to view the writing table.
So various routes have been learnt.
The one I want to point out is the one in the writing table of Rato one this network has been added
by E-I GOP d indicates the GOP as the routing protocol that added to the rot.
So we've got multiple routes but this route is the one of interest.
So we should be able to paying for that for that for that for which we can that's the loopback of Rado
for to get to that network.
We go via 10 1 to 2 and then 10 140.
In other words it's going via this link.
And then this link to get to the loopback of Route A for let's have a look at which routing protocols
are running on the road show IP protocols shows us that is enabled we are running OSPF on all interfaces
on the router UI job is also enabled on this router and so is up.
So Rotto one has three routing protocols enabled.
Now typically you won't do that in the real world but we are doing that here to prove a point.
So let's look at the OSPF database to show IP speak a database in the OSPF database.
We have a run of ID 4 out of four.
In other words that ROFFT exists in the OSPF database.
So why is OSPF not chosen for those ROFFT SPF is being used for this route.
But it's not being used for this Schrott.
Why is that.
So to help troubleshoot we can use the following commands show IP OSPF interface brief OSPF is enabled
on both interfaces of Rodda one show I.P who is a neighbor but it only has a neighbor relationship to
broaden to show IPTA GOP neighbor young Job he only has a neighbor relationship to rodder three.
Now in this typology I didn't enable the GOP on Rodda to router to only has OSPF enabled on rattus three
in this typology.
We only have enough GOP and ripp enabled but on Rodda too it is learning about the network 4.4 that
4.4 through OSPF from Rodda for Sarada to he's able to ping that loop back.
But on route one the network is not shown in the writing table and that's because of administrative
distance UI GOP has an administrative distance of 90 who is has an administrative distance of 110.
In other words if a road is such as Rato one learns about a network such as Ford or Ford for 4.4 from
both and OSPF router and in each job the router the GOP Rodda is deemed to be more reliable.
It's more believable.
The lower the administrative distance the more believable a route.
In this example I always P.F. has a higher admin distance when compared to your job.
So to get to this network your GOP is believed because it has a lower administrative distance when compared
to SPF.
So for both the loop backs of rotisserie and Rodda for the GOP is used but who SPF is used for the Lubeck
of Ratatouille.
So let's concentrate on the network your job used at the moment so on rotas 3 this is the configuration
of your job.
If I shut down the link on rodders 3 so I'm going to shut down the sport.
That means Rodda 3 will no longer advertise network for 4.4 to Tarrar one.
What happens now.
And what you'll notice is the entry is now replaced with an OSPF ROFFT And if we trace to quadruple
for it's going via routed to if I know shut that link on Rodda 3 the links should come up and your GOP
should advertise the rot once again on Route 1.
The road is replaced with an easy GOP entry rather than an always P.F. entry because the GOP has a lower
admin distance than I was P.F. does.
So your GOP is chosen rather than always P.F..
So just to prove the point again or shut the interface.
The interface on router 3.
Before I did that and job he wrote was used but now and always be if route is used tracing to that loopback
its not going via OSPF no shut the link to a Trace again.
Still hasn't switched over yet.
Let's try again.
Notice it went from that to us so different path was taken.
So because both your GOP and OSPF are advertising the same network.
There is a conflict and only one entry can be put into the writing table because the GOP has a lower
head minister of distance than OSPF your job he by default has an admin distance of 90 for internal.
Your GOP rants always P.F. has an Edmund distance of 110 and because of that job he was chosen.
I'll cover other scenarios based on this policy and separate videos.
I hope you enjoyed the video.
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I want to wish you all the very best.