[MUSIC] Welcome to the Interface Types and Configuration Module. By the end of this module, you should be able to describe interface types and basic interface configuration tasks. Interfaces are primarily used to connect the device to a network. However, some interfaces are used to provide a service or a specific function for the system on which it operates, on platforms running Junos OS, several types of interfaces exist. Management interfaces are used to connect the device running Junos OS to a management network. The actual designation for this interface is platform specific. Examples include FXP0 and ME0. Internal interfaces are used to connect the control and forwarding planes. The actual designation for this interface, is platform specific, examples include, FXP1 and EM0. Network interfaces are used to provide media specific network connectivity. Some media examples include ethernet, SONET, asynchronous transfer mode, or ATM, T1 and DS3. Loopback interfaces are used to provide a constant and dependable hardware independent interface. The Loopback interface uses the lo0 designation on all platforms running Junos OS. Use the lo0 interface in conjunction with routing protocols to facilitate routing in a redundant environment that is independent of the individual physical links within that environment. You can configure a single logical unit for the lo0 interface for each routing instance. Each logical unit associated with a given routing instance can, however, have multiple configured IP addresses. Services interfaces are used to provide one or more user configurable services such as encryption, tunneling and link services. Services interfaces can be provided through a physical services interface card or through software. Services interface is provided through a PIC, do not have ports or media associated with them, but have two letter interface type designations has shown in this table. Junos OS uses a standard naming convention. Most interfaces have names based on the interface media type, the system slot number in which the line card is installed. The line card slot number in which the interface card is installed and the port number for the interface card. The CLI almost always refers to line cards as flexible PIC concentrators, or FPCs. And interface cards as picks, even though the actual names of these physical components might vary between Juno's devices. For platform specific information, including details pertaining to the interface naming convention, please refer to the Juniper Tech Library website. You can access the website from the reference links document. In typical deployments, the slot and port numbering begin with 0 and increments based on the system hardware configuration. The example shows a sample interface name that illustrates the interface naming format. The highlighted interface name is for the fourth physical port. Number 3, on a gigabit ethernet interface card installed in the third slot, number 2 of a line card that resides on the first available line card slot, number 0 of a chassis. Other interface name designations exist that do not adhere to the naming convention. Interfaces with specific designations are created by Junos OS and are not directly associated with or dependent on physical interfaces. Some examples are, lo0, Loopback Interface. AE, Aggregated Ethernet interface. AS, Aggregated SONET interface, and vlan, VLAN interface. Junos OS also creates a number of internal interfaces. These internally generated interfaces are non-configurable. Some examples are GRE, MTUM, IPIP, and TAP. Note that interface support varies between the different Juno's devices. For support information always refer to the technical documentation for your specific product. Each physical interface descriptor can contain one or more logical interface descriptors. These descriptors enabled you to map one or more logical, sometimes called virtual interfaces to a single physical device. Creating multiple logical interfaces is useful in environments where multiple virtual circuits or data link layer connections are associated with a single physical interface, such as in ATM and frame relay networks. Some encapsulation such as the point to point protocol or PPP, and the Cisco high level data link control or Cisco HDLC protocol, support only a single logical interface and it's logical unit number must be zero. Other encapsulation such as frame relay, ATM and tagged ethernet support multiple logical interfaces so you can configure one or more logical unit numbers. The unit number and the circuit identifier, are different in meaning, the circuit identifier, identifies the logical tunnel or circuit, whereas the unit is used to identify a logical partition of the physical interface. Although not required, it is generally considered a best practice to keep the unit number and circuit identifier the same. This practice can greatly aid in troubleshooting when you have many logical circuits. Junos OS devices can have more than one address on a single logical interface. Issuing a second set command does not overwrite the previous address, but rather adds an additional address under the logical unit. The example displays the use of the CLIs rename command, which is an excellent way to correct addressing mistakes. Also, note that Junos OS forms Interior Gateway Protocol or IGP adjacencies over all subnets when the IGP is configured on a logical interface. This behavior is worth noting because some vendors products form an adjacency over the primary address of an interface only. Certain physical interface properties can be adjusted. You can change the data link layer protocol for a particular media type, for example, PPP2 Cisco HDLC, and you can turn keep a lives on or off. On ethernet interfaces, you can hard code the duplex setting to either half duplex or full duplex. You can specify the link speed on certain interface types. You can vary the MTU size from 256 to 9192 bites. Clocking refers to the interface clock source, either internal or external. Scrambling refers to payload scrambling, which can be on or off. You can modify the frame check sequence or FCS to 32 bit mode, the default is 16 bit mode. You can also enable local or remote loopbacks or set up a bit error rate or BERT test. Some logical interface properties include protocol family, which refers to the protocol family you want to use such as family inet, inet6, ios, mpls, or bridge. Addresses, which referred to the address associated with the particular family, for example, IP address using family inet. Virtual circuits, which refers to the virtual circuit identifier such as a data link connection identify or or DLCI. Virtual path identifier or VPI, virtual channel identifier, or VCI, or VLAN tag. Other configurable options include, inverse address resolution protocol, or InARP, traps, and accounting profiles. All interfaces have the same configuration hierarchy organization, Junos OS considers all properties defined directly under the interface name to be the physical properties of that interface. The unit number represents a particular logical interface or sub interface. Junos OS considers all properties defined directly under the unit number to be the logical properties of the corresponding sub-interface. This is a basic configuration example that includes multiple interfaces. Multiple protocol families configured under a single logical unit and multiple IP addresses configured for a single protocol family, while a single logical unit does support multiple protocol families, such as inet and inet6. You cannot configure a second protocol family in conjunction with the ethernet switching protocol family. This example illustrates this point, the example also highlights the use of the preferred and primary configuration options. The preferred option is used when you have multiple IP addresses belonging to the same subnets on the same interface. This option enables you to select which addresses used as the source address for packets sent by the local system to host on the directly connected subnets. By default, the numerically lowest local address is chosen, in the example, the default behavior has been overridden with the preferred option, making 172.19.102.2/24, the preferred address. The primary address on an interface is the address that is used by default as the local address for broadcast and multicast packets sourced locally and sent out the interface. The primary address flag also can be useful for selecting the local address used for packets sent out unnumbered interfaces, when multiple, non 127 addresses are configured on the Loopback interface, lo0 by default. The primary address on an interface is selected as the numerically lowest local address configured on the interface. In the example, 172.19.102.1/24, is the primary address for the ge0/0/2.0 interface. Because it is the numerically lowest address configured on that interface, 192.168.200.1/32, is the primary address for the lo0.0 interface, because it is assigned the primary option. Interface support varies between Junos OS devices. Refer to the technical publications for detailed information for your specific product. To quickly verify the state of an interface, you can issue the show interfaces terse command. To filter the displayed output to an individual interface, add the name of the interface, instead of a name, you could also use a wildcard, for example, ge*, to match all gigabit ethernet interfaces. In the sample output, you can find the admin and link status, the protocol family details and the address information for the specified interface.
