This flock is a continuation of a previous blog discussing administrative distance or the believability
of a routing protocol.
In this example we've got four routers Rato one Rodda to write history and write a full Rodda to in
the apology.
He's only running away if we can see that by using the show IP protocols command.
It has a relationship with both rodder one and wrote a full rodders three in the apology he's running
up and GOP now in the real world you typically don't enable a whole bunch of writing protocols on your
is we doing it here to explain that Mr. of distances.
So show IP protocol and Rotto one rat of one is running rip your GOP as well as OSPF Rotto for he's
doing the same.
So on route of one show IP route the route of interest in this typologies could ripple fall.
That's a loop back on Route 4.
We can see in the writing table of Rato one that the rumped appears in the writing table and the protocol
selected was GOP.
That's because the GOP has an administrative distance of 90 which we can see here.
SPF has an image of distance of 110.
The loopback of Route 2 has been learnt via OSPF because we are not running the GOP on a t.
The lower the administrative distance the more believable the routing protocol.
So this ROFFT was selected because your job has a lower admin distance show IP OSPF database shows us
that the route is available in the OSPF database but the GOP was selected because it has the lowest
administer of distance.
So at the moment show Bruhn section GOP shows us that the GOP is enabled on right of one.
So if we remove the GOP from rodded one and then look at the routing table what you'll notice is that
the rot has been added from OSPF the next hop is via a 10 1 1 2.
If we scroll up previously the next top was tendered one to 1 to 2 which is routed three but because
my job is no longer running on Route 1 The route is now available via Route 2 and was lent through OSPF
So as an example if we trace to that route.
Now notice that it goes via rodded too.
We are still running up on this router so is running a rotas 3 router 1 and a full but the route is
not selected for quadruple for because a rep has a higher administer of distance when compared to P.F.
So the loopback of router 3 is advertised via up to one.
And because I was P.F. is not advertising that route the route is put into the writing table but because
I always be advertising this route and it has a lower administered distance when compared to up the
OSPF route is used not route so to confirm that and try and prove it to you.
I'm going to remove job P from router 3 serratus 3
is running up.
It's not running IGMP rope is the only running protocol running on road 3 to 1.
We can see the loopback of router 3 learnt via a rep but we don't see the loop back of router for because
OSPF takes precedence so let's remove who is P.F. show IP rot we haven't learnt about the route through
yet.
So let's do some investigation to make sure things are working.
Show IP wrapped on rotatory.
Notice the rot has been learnt via a rope on Rotto one.
It's now available.
I was a bit impatient.
Takes longer to advertise routes so now paying quadruple for trace could ripple for it's going via a
router 3.
And that's because the only routing protocol that's running on Route 1 is reep So the writing table
is populated with broths the reader won't be able to ping the Lubeck of Ratatouille because Gruppe is
not running on Rodda too.
So we need to enable replan right to feed one for connectivity in the network.
But for now I'm not going to do that.
I want to prove to you that OSPF takes precedence.
So notice the wraparound isn't the writing table with an administrative distance of 120 counties to
it's available via tendered one to two to two.
It's been in the writing table for 19 seconds and it's available via a gigabit 0 1 that's lets enable
OSPF network and all the naval P.F. on all interfaces show IP OSPF neighbor.
We have a neighbor relationship with reality show IP route.
Notice the writing table has been updated always takes precedence over ripe so the path you use to get
to quadruple four is via router too.
If we enable the GOP on this Rodda
traffic will still go via rodded too because we need to enable the GOP on Radio 3 so let's do that Rodda
you know job P enable your job and all interface's neighbor relationship has been established.
So show I.P your job.
Neighbor neighbor relationship is available show IP rocked the GOP Raat has now been put into the writing
table.
And if we trace that loop back it's going via router three site administer distances work as follows.
The lowest number wins.
Different routing protocols have different administrative distances set by default.
You can change them.
Wrap is 120 SPF is 110 hijo internal Roths is 90 but I could as an example add a route to the writing
table steadily at a static route to force the traffic to go via rockety.
Now when we look at the writing table notice the static route has replaced the GOP because a static
route to a next top IP address has an admin distance of one.
Is nothing more believable than you as in the router believes you more than it believes a algorithm
such as your job is P.F. and thats because you know what you are doing and the rodded believe you more
than the police or the rodders.
So once again trace via wrote a TV show run popping clewed rot.
We've got the static route forcing the traffic via roads to well remove the static ROFFT should not
be dropped.
Your job is the most believable now
traffic is going via road history.
Remove your choppy
always be fraught takes precedence.
Now traffic is going via router too so that is a demonstration of ministry of distance or the believability
factor of a rant for the CCMA exam.
You need to know admin distances in a separate video.
I'll show you an example with BGP.
Hope you've enjoyed the video please like it please subscribe to my YouTube channel.
I wish you all the very best.