Router on a Stick

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Router_on_a_Stick

How to config a Router on a Stick.

What we might do in a regular network is have a couple of switches. And then have our hosts and then route between them just as you see here. And another topology we might have the switch actually broken up into a couple of islands and then route between them. Again with the same router. But what happens if we want to connect another router to the topology. And all of these ports that happen to be Ethernet.

Well we find out that on a lot of our routers we only have two Ethernet ports and one way out of that situation. Is to use. Router on a stick. And so that’s what we’re gonna do today. So what we’re gonna do is connect our topology up like this and only use one even at port on the router. But we’re going to use some interfaces on that particular interface. And on the switch with the villains we’re gonna setup a trunk line. All right. Normally routers have no idea that villains are are happening.

So if you were to ask the routers in these two technologies about the villains they would have no idea. This configuration is going to give the router some knowledge of the villains. So let me close out a Visio here. All right first up we’ll take a look at our switch. So I haven’t done anything yet except configure the two IP addresses for the hosts.


Interface range command

So we take a look at our B lands here. You can see that everybody’s in B land one. So what I’m going to do is. Set up. Two v lines. And I’m using. A particular set of V lands for a reason. So I’m using the interface range command here. And then 10. And then we’ll do. Some. 12. And we’ll use 20. Okay. So now if I do show we’ll and we can see that I’ve got a bunch of port in these two V lines but I haven’t set up my. Trunk line. So I like to specify what I’m doing I don’t want the switch to figure it out. So what I’m going to do is. Change this guy to a trunk port. Those two things that I have to do I’d use the mode command to tell it that but I also got to specify.

The encapsulation that I want to do. And so I may use that one. Such port. Sorry I forgot that. Okay. We’re gonna use. An encapsulation type specified by Tripoli you go to that one. Q. And then we’re going to do switchboard mode trunk. Now on a lot of Iowa’s versions it’ll grouse about the order. So this is the order that you want to do it. And that’ll about do it for our trunk lines. So let me take a quick look at my router now. So I’m just going to switch over. And you can see that I’m on my. Router now. And I have no configuration here.

Now I am wired to port 0 slash 0. I think. Yep 0 slides 0. So when I do all make figure nation it’s going to exist on 0 slides 0. 1 1 I’m going to do is interface 0 slash zero. Dot. 10. And what that does is it puts me on the sub interface on that particular interface. Now there’s two things that I have to do here. One is I need to give it an IP address. So this is just going to be the default gateway on that side. So if we take a look here this is actually we’re going to make it to be land aware so we’re going to maintain the same encapsulation standard. And then a motel it would be land.


Now it’s not going to credit me about The order of my operation here. Now I’ll take a moment here to indicate what I was talking about. IP addresses and VLAN I.D. and sub interfaces. I set up VLAN 10 and V land 20 on. My switch. So I’m going to also set up some interfaces 10 and 20 on my router interface and I’m going to use the 10 and the 20 networks. It’s a really handy way of going about things. So you don’t forget so that you always match up numbers and sub interfaces and VLAN I.D. and subnet. So I’m going to do the exact same thing.

The connection point is the sub interface

So I’m interface 0 not 20. And we’ll do. A line. 20. For the encapsulation up to the router. And then You just get the default gateway for that site. Now let’s take a quick look at our. Routing table. Well. I suppose it helps. If I turn on the interface. Now my switch is gonna go through spanning tree discovery because I have a pretty. Plain. Configuration. But here is my routing table. Note that I’m directly connected to these two networks. But. The connection point is the sub interface. So that’s pretty much it. I’ve got 10 down to 54 and. 20 about 250 for. And let’s see.

How well this works. So first we’ve got. This node being 10 to 1. And I’m going to ping. Turned 250 for a look the router is alive and well. Okay so let’s ping the other side of the router and I’ll bring this up a little bit so you guys can see a little better Groups. So that’s the other side of the router or really the other side of the interface.

The other sub interface and lastly is the node on the other side of the router. Now just to polish this off. All right. So to be clear what’s happening is that transmissions from this particular node are going up to the router on one interface and then turning around on that same interface and coming right back down to the other node. And there we have it.

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