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This is a free, complete course for the CCNA.
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If you like these videos, please subscribe\n
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Also, please like and leave a comment, and\n
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If you want more labs like this, I highly\n
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NetSim is a network simulator like Packet\n
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over 100 detailed guided labs covering the\nCCNA exam topics.
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If you want to get NetSim, follow the link\nin the description.
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In this lab we will configure a GRE tunnel\nbetween R1 and R2.
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Both routers are connected to a service provider\n
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virtual direct connection between them.
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Now, all traffic between R1 and R2 will still\n
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However all packets will be encapsulated in\n
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that the original packets pass through.
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Now, as I mentioned in the lecture video GRE\n
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However the purpose of this video is just\n
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GRE because it’s quite simple to configure.
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So let’s get right into configuring GRE,\non R1 first.
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CONF T. To configure a GRE tunnel, we have\n
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This is not a physical interface, of course,\n
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Okay, I have created the tunnel interface.
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Now I just need a few commands to complete\n
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First, TUNNEL SOURCE, and now we have to specify\n
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Well, we should use the interface connected\n
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Next, TUNNEL DESTINATION, and then we have\n
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So, I’ll enter R2’s WAN interface’s\nIP, 200.0.0.2.
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And finally, the virtual tunnel interface\n
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IP ADDRESS 192.168.1.1 255.255.255.252.
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Okay, that’s all the configuration needed.
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TUNNEL SOURCE, TUNNEL DESTINATION, and then\nIP ADDRESS.
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Okay, the Tunnel0 interface is up/down.
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We’ll investigate that after configuring\nR2.
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So let’s do the same thing on R2.
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TUNNEL SOURCE, and just like on R1 it will\nbe G0/0/0.
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TUNNEL DESTINATION, this time it will be the\n
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IP ADDRESS 192.168.1.2 255.255.255.252.
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Okay, that’s all, let’s check the status.
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Okay, there’s the tunnel interface, but\nit’s still down.
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Why is that, even though we’ve configured\nboth sides?
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So, R2 doesn’t have a connected route for\n
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It has connected routes for its physical interfaces,\n
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R2 doesn’t know how to reach the IP address\n
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If R2 doesn’t know how to get to 100.0.0.2,\n
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I’ll just configure a default route.
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IP ROUTE 0.0.0.0 0.0.0.0 200.0.0.1.
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Okay, after we have the route to 100.0.0.2,\n
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Now we have the connected route for the tunnel.
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Hmm, the ping still isn’t working, even\n
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Actually the reason for that is that we also\n
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Let’s check the routing table on R1.
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Only connected routes for its physical interfaces,\n
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I’ll configure a default route here, too.
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IP ROUTE 0.0.0.0 0.0.0.0 100.0.0.1.
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Okay, now the tunnel interface comes up, and\n
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As usual the first few pings might fail because\n
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but after ARP completes they will succeed.
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So, although R1 and R2 aren’t directly connected,\n
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through the GRE tunnel, and soon you will\n
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But first, let me show you a ping in simulation\nmode.
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Okay let’s check the contents of this message\nthat R1 sends.
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Click on outbound PDU details, and let’s\n
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So, there’s the ICMP message, the ping.
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It’s encapsulated with an IP header, source\n
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the addresses of the tunnel interfaces.
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But then on top of that there is a GRE header,\n
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In this outer IP header, the source IP is\n
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destination IP is 200.0.0.2, R2’s G0/0/0\ninterface.
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The original packet from R1’s tunnel interface\n
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within an additional IP header which is used\n
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service provider network to reach R2.
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Now, something you can do when R1 and R2 are\n
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make them OSPF neighbors to share routes.
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First let me demonstrate that a ping from\n
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Let’s wait a bit for all the pings to go\n
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But when R1 and R2 become OSPF neighbors they\n
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and PC2 will be able to communicate over the\nGRE tunnel.
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So let’s enable OSPF on R1 first.
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I’ll enable it on the tunnel interface,\n
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NETWORK 192.168.1.1 0.0.0.0 AREA 0.
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That enables OSPF on the tunnel 0 interface,\nnext G0/0.
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NETWORK 10.0.1.1 0.0.0.0 AREA 0.
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And I’ll make G0/0 a passive interface since\n
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Okay now I’ll do the same on R2.
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NETWORK 192.168.1.2 0.0.0.0 AREA 0.
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NETWORK 10.0.2.1 0.0.0.0 AREA 0.
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And again I’ll make G0/0 a passive interface\n
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Okay, and as you can see R1 and R2 have become\nOSPF neighbors.
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Okay, it learned a route to 10.0.1.0/24, R1’s\n
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And I’ll go back to check on R1 also.
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Okay, it learned a route to 10.0.2.0/24 via\n
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Okay, let’s try that ping from PC1 to PC2\n
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One or two pings might fail, but after that\nthey will work.
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R1 will encapsulate the packet from PC1 using\n
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Okay, in this video I introduced GRE tunnels.
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You don’t need to know this for the CCNA\n
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helped you understand a little about how tunnels\nwork.
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Now let’s take a look at a bonus lab in\n
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