44. Interface Naming Conversion
Let’s understand the interface naming convention on a Junos device. Junos uses a standard naming convention for its interfaces, and most interfaces are named as type hyphen FBC Forward/Pich Forward/port type represents the type of interface which is gigabit Ethernet or Fast. Ethan Net FBC stands for Flexible Pig Concentrator. In simple words, it represents the line card. Slot number. PIC stands for physical interface card in simple words. It means your interface card, slot number and then the port is the port. No.
So here’s an example, G.E. one 0 one. So G.E. represents gigabit Ethernet. The one that you see here is the FBC, which is the flexible pig concentrator, also known as the line card. Slot number 0 represents your pick, which is your physical interface card or in simple words, interface, card, slot number. And the one here represents your port. No. So here I have the cross section of a Junos device. On this Junos device, we have to line card slots. The one at the bottom is called FBC 0 and the one at the top is called as FBC one on every line card.
We have to interface card slots. So two interface slots on FPP 0 and two interface slots on FBC one. The one on the left is Pigg 0 and the one on the right is pick one. And the same applies to FBC one. The one on the left is Pigg 0 and the one on the right is pick one. Every interface card has four ports and the port numbering starts from 0. So you have interface 0, one, two, three. And that applies to every interface card.
So the line card is called as FBC within your line card. You have the interface card that is called ASPEY icy physical interface card and within every interface card you have these ports. Now, depending on the platform, you could have four ports, eight ports, twelve ports, 24 ports and so on. This is a very simplified version of a Juniper press X device. OK. Let’s do an exercise together first. I’m going to remove all these labels and let’s see if we can find out where a specific interface is. So let’s see if we can find out where G.E. one one one is, the assumption here is that all of these interfaces are of type G.E.. So let’s find out where G.E. one one one is.
Take a moment, pause the video if needed, and try to find out where G.E. one one one is. OK, now I’m going to tell you the answer, G.E. one one, one is there. And if you’re wondering why is that so? The reason is the first number here is your FBC. So this is FBC 0. And this is FBC one. The next is your physical interface card. This line here represents Pigg 0. This one represents. Pick one. And within that, we are looking at interface number one. So that is G.E. one one, one. Let’s try one more example. Can you identify where G e0.0.0is past the video if needed? Take a moment and figure out where G e0.0.0is. All right, so I’m going to show you now where that port is, and it’s right over there. If you’re wondering how the reason is we are looking at FPP 0, which is this FBC here or this line card over here. We are looking for Pigs’ 0, which is this pic over here, and we’re looking for Port 0, which is ported over here. Now, let’s do one more example. The last one. Find G.E. one one three. FBC one, pick one, part three. So the answer is here. If you’re wondering how so? This is FBC one, this is pick one. And this is PT. three on the screen. Now I have another cross section of a Junos device, similar to what we saw earlier.
This is the cross section of a Amex 80 router. But the interface naming convention is the same. So here we can see we have two line cards. The one at the bottom is FBC 0 and the one at the top is FBC one and FBC one is divided into four interface slots. So you have picked 0. Pick one, pick two and pick three. And every interface card slot has these interfaces marked over here. An important thing to keep in mind is that some interfaces do not follow a naming convention. Examples include L.O. 0, which is the loopback interface. You have the interface, which is the aggregated Ethernet interface. You have A. S, which is aggregated Sonnett interface. And then you have V, which is the VLAN interface. So most Junos interfaces follow a naming convention. However, there are exceptions. Some interfaces may not follow an interface naming convention.
45. Interface Properties
Let’s now talk about Junos interface properties. Junos interfaces have two portions. So every interface that we can figure will have a physical portion. And it will also have a logical portion, which is referred to as a unit at both physical and logical levels. We can configure certain properties. So let’s talk about them. We’ll start with the physical properties. These are properties or settings that you will configure at the physical interface level. The first one is mode. So you can configure if the interface is going to operate in half duplex or full duplex mode. We can also configure the speed, which is basically the link speed. We can configure the empty you, which is the maximum transmission unit, which can be defined as the largest packet size or the largest frame size that you would like to send on the network. And this value range is between 256 and ninety one ninety two bytes.
We can also configure the clocking source. Do we want to use an internal or an external clocking source? Another thing that we can configure is frame check sequence, which is used for error detection and we can also configure encapsulation. This includes types like P.P., which is point to point protocol, frame relay PBB over Ethernet, etc.. Now let’s look at the logical properties. At the logical interface level, you can configure the protocol family. I know it is IPv4 high net six is IPv6. You then have other protocols like ISO, MPLX less and Ethernet switching. Next, we can configure the address, which is the IP address. Make a note that the IP address is a property of the logical interface, not the physical interface. We can also configure V and tagging and add firewall filters or routing policies on the logical interface. These are not the only physical and logical properties that we can configure. In fact, there’s a whole list of properties that we can configure. But we’ve looked at the most common properties that you’ll likely to configure before we jump onto the Junos device and take a look at this.
Let’s understand the interface configuration hierarchy. So at the top, you have the edit interfaces hierarchy under which you have the physical interface under the physical interface. You would configure the physical properties and under the physical interface, you can also enter the logical interface configuration mode using the keyword unit. So we can enter unit 0, unit one and so on. So under the unit or the logical interface is where you would configure the logical properties. Now let’s jump onto the device. All right, I’m here at a Junos terminal. I’m first going to enter the configuration mode or the operational mode with the CLI command and then enter the configuration mode with the added command. Let’s try to configure and interface. So let’s enter edit interfaces G 0 0 0. Right now I’m at the physical interface configuration mode. So if I do set space question mark here, we can see all the physical properties that we can configure. For example, we can disable this interface, we can apply a description, we can set the encapsulation, we can configure the link mode, we can configure the MAC address the maximum transmission unit. We can also configure the speed of the interface.
And notice here, we can use the unit keyword to get into the logical interface configuration mode. You see the VLAN tagging keyword that is only to enable support for v lan. Tagging and tagging is not a property of the physical interface. It’s a property of the logical interface. This keyword here only allows you to enable support for v lan tagging. Now let’s enter the logical interface, so I’ll do edit unit 0. And now we are under the physical interface and also under the logical interface. So if we do set space, question mark, we can see all the logical properties that we can configure, like the bandwidth. We can provide a description. We can disable the logical interface. We can set encapsulation here as well. We can set the protocol family. We can also set the VLAN I.D. and the VLAN tags. So the key takeaway here is to understand that properties of interfaces on Junos devices can be configured at two levels. You can configure it at the physical interface level or at the logical interface level.
46. Interface Address Configuration
Now let’s understand how to configure an IP address on the Junos interface. Let’s start with the Junos terminal. All right. So I’m here at the terminal and to configure and interface IP address, I’m first going to enter the interface configuration mode. So I’ll say edit interfaces Grzegorz 0 0. So right now I’m under the physical interface configuration mode, but we know that IP addresses are configured at the logical unit. So I’ll say edit unit 0 and now I’m under the logical interface configuration mode. When I do search based question mark, you will notice that right away. We do not have the option to configure the IP address and that’s because IP addresses are configured under a protocol family. So we first need to enter a specific protocol family. So let’s do that. Also edit space, family space, question mark. And here’s the options available for protocol families. I’m going to pick inet for IPv4 and now will be able to configure the IP address, set space, question mark and we can see that we have the option to configure and address. So let’s do that set address and I am going to provide an IP address here. Let’s do 10 one one one 24. Press enter. And if we do a show now, the address has been configured. Now, let’s say I wanted to change this address, I want to change it to 10 one, one, two, how would I do that? Let’s try with that space, question mark and let’s try set address again. Let’s provide a new address this time, 10 one one two twenty four. And if we do a show now, do you notice something? We now have two addresses under the same interface.
Let’s talk about this. So Junos devices can have more than one IP address on a single logical interface, just like we saw right now, when you issue a second set command. It does not override the previous IP address, but rather adds an additional address under the logical unit. So to change an existing address, we should use the renamed command or the delete command. Let’s give this a try. All right, I’m back over here, so let’s say we wanted to change 10 one one one two ten one one, two. Before we do that, I’m going to delete this address. Delete address 10 one one to 24, so now we only have one address remaining, let’s first start with the rename command. In fact, let’s start with a question mark and we have the option here to rename a statement. So rename Questionmark. We are trying to rename and address and the address we are trying to rename is ten one one one twenty four. The keyword is to. And the next keyword is address. And now we can provide the new address, which is 10 one one two twenty four. And now if we do a show command, we can see that the address has been changed. Let’s say we now want to change this to 10 one one three and we want to use the delete command. So we would say set address ten one one three twenty four.
So if we do a show now, we should see both the addresses and now we use the delete command to delete the first address. Ten one one two twenty four. And now if we do a show, we now have only one address remaining. Now let’s say we have two addresses under the same interface. So let’s say we have ten one one three and ten one one four twenty four. So if I do a show here, we now have two addresses under the same interface. So if I try to send traffic out this interface, which address is going to be used by the device? Is it going to use this one or is it going to use this one? Now, as an administrator, we have a way to influence this. So if I do set address ten one one three twenty four, question mark. Notice we have the option to specify this as a preferred address or as a primary address. Let’s talk about this back over here. Let’s start by talking about the preferred address. This is used when you have multiple IP addresses belonging to the same subnet on the same interface.
Using this option allows you to select which address will be used as the source address for packets sent to hosts on the directly connected subnet by default. This is going to be the numerically lowest address. So the preferred address option allows us to influence which address will be used as the source address for packets sent to hosts on the directly connected subnet. So this is how the configuration would look like this is a similar configuration that we were looking at, so underachieve 0 0 0. We have two addresses, 10 one one one and ten one one two. By default, the numerically lowest address will be taken as the preferred address, but we have the option to influence this by setting another address as the preferred address. Let’s now talk about the primary address. The primary address is the source address for broadcast and multicast packets. These packets are important from a routing configuration perspective. By default, Junos makes the numerically lowest address as the primary address. Again, we can influence this by setting the keyword primary under the interface configuration, so in this case, you can see we are configuring the Lookback interface because the Lubeck interface is very commonly used for routing configuration.
And here we have two addresses, one 90 to 160 at one point one and one 100 by default. Junos would use the first address because that’s the numerically lowest address. But let’s say we want to use this address for broadcast multicast so we can set that as primary. An interesting thing to note is that Junos supports multiple protocol families on the same interface so you can have an interface that looks like this under the same physical interface, under the same logical interface. You now have two families operating. The first one is IPv4 and the second one is IPv6. Let’s see how to configure this on the device. All right, so I’m back over here and let’s do a show first. So we are under a family in. Now we are going to go one level up and we are going to edit family unit six, which is the IPv6 protocol family, and we can do a set address. And will provide an IPv6 address press enter and let’s do a comment. And now we can see that. We have two protocol families operating under the same logical interface.
