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Locating an IP Address

You may hear the term IP address as it relates to online activity. Learn how to locate your IP address or someone else’s IP address when necessary.

What Is an IP Address?

IP stands for “internet protocol.” An IP address identifies your computer or your device by an internet number in much the same way your house or apartment has a number that identifies it on your street. Your IP address enables you to have a connection to the internet by following the set protocols and specifications set up for these connections.

A common type of IP address is known as an IPv4 address. This IP address has four three-digit numbers separated by dots. Without your IP address, you can’t connect to the internet, send information or retrieve information. A newer type of IP address is called the IPv6 address. This IP address has eight separate clusters of four hexadecimal digits, separated by colons.

Why Find an IP Address?

If you know someone’s IP address, you can discover some information. An IP address won’t show someone’s name, phone number or exact physical location, but it should reveal the general geographic area. The geographic location revealed by an IP address look-up may be very close to the user’s location, or it might be hundreds of miles away. An IP address will show the internet service provider used as well. Law enforcement typically looks up IP addresses to find ISP information. An online retailer will often use an IP look-up tool to make sure that consumers placing orders are located in the general vicinity of the mailing address associated with a credit card. An IP address can also verify someone’s general vicinity if fraud is a possibility.

How to Locate an IP Address on a Website

You have a couple of options for finding an IP address associated with a website. On a Windows operating system, open the command prompt and enter “ping” and the web address of the website. Click “enter” and your computer will search for the IP address to display it. Once you have the IP address, use an IP look-up tool to get more information. Navigate to a website such as “” and enter the IP address in the search field to see information about the general vicinity of the IP address.

What’s My IP Address?

If you’re curious about your own IP address, you can use the IP look-up tool to learn your own number. Again, navigating to a website such as “” will get you the information you want. Once on the website, the tool will detect your IP address and display the number.

Get an IP Address From an Email

If you get an email and you want to know the IP address of the sender, you can check the header to find out. Most email browsers have an option to display email headers. With an email message open, look for a setting option called “headers” or “internet headers.” Once you find it and turn it on, identifying information for the email message will display, including the sender’s IP address. Some people will modify email header information, so it’s smart to verify an IP address by using the command prompt ping process.


assign ip address to juniper interface

Configure IP Address in JunOS

Are you new to Juniper Networks ? If yes then I am sure you are having hard times configuring IP address in Juniper device’s interface. Today I will show you how to configure IP address in JunOS or Juniper devices. Before showing you the commands in configuring IP address lets begin with some basics.

Well, there are different modes in  JunOS like Cisco IOS. The modes are Operational Mode and Configuration Mode. You can configure IP address in JunOS operating system in Configuration mode only. In JunOS everything you configure for interface is logical. Unlike Cisco IOS, when you configure IP address in a JunOS interface then you are actually creating logical interface and configure IP address in that logical interface. The logical entity is called unit and is given a number starting with zero “0”. Most of the times you will configure IP address in logical unit 0.

JunOS supports many protocols. IPv4 and IPv6 is the protocol ( family ) that you will be using most of the time. JunOS calls inet for IPv4 and inet6 for IPv6. So you have to mention the family inet or inet6 while configuring IP address in Juniper router’s interface.

Let’s see an example of how IP address is configured. We will configure IPv4 address on ge-0/0/0 interface.

Here, IP address is assigned on logical interface ge-0/0/ 0.0 interface of IPv4 family. You can view this information by typing the following command,

Now let’s see another example for configuring IPv6 address in ge-0/0/0 interface.

Here family inet6 is used to specify IPv6 address. To view the configuration you can use the show command.

This command will show you information about this interface in detail.

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Configure Private VLANs in Juniper Switch

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Interface Configuration Examples

A walkthrough of configuration examples, starting with basic examples and then getting into a few more complex configurations, will help to put this into perspective. The order of the walkthrough uses the following configuration examples:

Gigabit Ethernet interfaces

Gigabit Ethernet with VLAN tagging

T1 interface with Cisco HDLC

Serial interface with PPP

Serial interface with Frame Relay

Aggregated Ethernet interfaces

GRE Tunnel Interfaces

Initially, we will use a step-by-step approach to establish the configuration fundamentals. Then the walkthrough will move toward configuration results that build on the fundamentals and become advanced. Once you grasp the fundamentals, you should be able to follow the advanced configurations. At the end of this section, we will discuss the use of the Virtual Router Redundancy Protocol (VRRP).

Gigabit Ethernet Interface

First, let’s build an interface on router Lager that connects directly to router Ale over the ge-0/0/0 interface.

Check the status of the ge-0/0/0 interface by issuing a show interfaces ge-0/0/0 terse command. Junos interfaces are automatically “enabled” when the physical connection is wired:

If an interface needs to be administratively disabled, issue the set interfaces <interface name> disable command.

The interface appears to be physically up, so next, configure the interface to allow IP traffic to flow as well as add an IP address. Begin by entering configuration mode, dropping down to the hierarchy of the interface, and configuring the correct family and local IP address:

Since this is a non-VLAN-tagged Ethernet interface, unit 0 must be used when configuring the logical properties of family inet.

Also, note that Junos requires a mask for every IP address in the classless interdomain routing (CIDR) “slash” notation. An absence of the mask can lead to the less desirable result of configuring a /32 subnet on your interface. (Look for other Junos address issues in Interface Troubleshooting .)

Verify the configuration and activate the changes by issuing a commit and-quit command:

Verify the status of the interface. Note that the status now includes the logical portion as well as the physical portion of the interface:

Lastly, test connectivity by issuing a ping command toward the other end of the link of Ale :

Notice the Ctrl-C sequence used to break out of the ping command. Junos will send an endless number of pings unless a break is issued or a specific number of ping packets are specified with the count command.

Gigabit Ethernet with VLAN Tagging

Continuing with our example, let’s add VLAN tagging between Lager and Ale , which is already configured with a VLAN ID of 100. The first step is to enable VLAN tagging on the physical interface of Lager :

Next, add a VLAN ID of 100 on logical unit 0:

Juniper routers do not have a default VLAN, as every VLAN must be explicitly configured. Many switches use a default VLAN of 1, so make sure you explicitly configure a vlan-id of 1 on the router for connectivity.

Although this is a valid configuration on unit 0, the best practice is to always keep the same unit number as the VLAN tag, so let’s change the unit number with the rename command:

Lastly, activate the changes, verify the interface status, and test connectivity:

Notice the use of the command run to issue the operational mode command ping in configuration mode.

Also notice the use of the top command prior to the commit command. In some cases a commit can be issued only from the top. Using top will save time otherwise spent issuing multiple commit commands.

T1 Interface with Cisco HDLC Encapsulation

The T1 interface is the most popular basic physical layer protocol used by the Digital Signal level 1 (DS1) multiplexing method in North America. For point-to-point interfaces on Juniper Networks routers, the default Layer 2 encapsulation is PPP, which differs from many other vendors’ default behavior. To quickly interoperate with those vendors, change the encapsulation to the default setting, which is usually Cisco HDLC. Since we already showed the step-by-step configuration in the previous configuration, we show here only the result of adding the correct encapsulation:

An inquiring mind may wonder why the encapsulation has the word cisco in it. Is there a non-Cisco HDLC? As a matter of fact, there is! There is a standard HDLC protocol (ISO 13239), used in protocols such as X.25 and SDLC. The original specification did not have multiprotocol support, so Cisco decided to create its own version with this support with different header fields and definitions. Although this protocol is officially proprietary, the workings are open and have been implemented by many different router vendors.

Serial Interface with PPP

A serial interface can come in a variety of different physical forms, such as V.35, X.21, and EIA-530. The choice of physical media often depends on geographical location; V.35 is the most common choice in the United States and Europe, and X.21 is more common in Japan. Regardless of physical media, all serial interfaces have the same idea of defining a data circuit-terminating equipment (DCE) device and a data terminal equipment (DTE) device. The DTE device is the end unit that receives data encoding, clocking, and signal conversion from the DCE device. In modern communications, the DCE device often takes the form of a channel service unit/data service unit (CSU/DSU) or a modem; however, when connecting two routers in a back-to-back fashion, one of the routers takes the role of a DCE.

Router Ale and router Bock have a back-to-back serial connection using V.35 with the default encapsulation of PPP. Normally, a router will default to DTE mode, but in this case, Ale is automatically chosen as the DCE based on the detection of a DCE cable. You can observe this detection in the Local mode field of the show interfaces command:

Since one of the roles of the DCE is to provide clocking to the DTE, an internal clocking mode needs to be configured on Ale . This allows Ale to generate a clocking signal toward Bock using the internal clock with a default clock rate of 8 MHz:

Bock has no clocking mode configured and takes the default clock mode of loop-timed, which takes the transmitted clock from Ale . Bock could also have been configured for DCE mode, which would have the same result in this case. Here is the Bock configuration:

You can verify the local mode, clocking mode, and clock rate on Bock by using the show interfaces command:

Clocking can often be a confusing topic for many users. For back-to-back router connections, Juniper made it simple by allowing multiple different clocking modes to be configured and still “do the right thing.” The only combinations that will not work for back-to-back connections are the DCE in loop mode and the DTE in loop or DCE mode. However, when connecting to a CSU/DSU or a modem, proper care must be taken to configure the correct clock mode.

Serial Interface with Frame Relay

Frame Relay is a Layer 2 encapsulation that enables the connection of your LAN via a WAN connection to a Frame Relay node. Frame Relay creates a tunnel called a permanent virtual circuit (PVC) over a private or leased line to provide connectivity to other sites over the Internet service provider’s (ISP’s) infrastructure. With the emergence of DSL and IP-based networks, Frame Relay is not often seen anymore, except in rural areas as a cheaper, “always on” connection.

To establish a Frame Relay connection with the Frame Relay node, the proper encapsulation of frame-relay (RFC 1490 ) must be configured as well as the local circuit identifier for the PVC represented by the logical property of a dlci number:

The router can also support back-to-back router connections by configuring one router to operate in DCE mode or by turning off keepalives on each router. If keepalives are disabled, the router will not wait for any local management messages to enable that interface. Also, turning keepalives off can help in troubleshooting by allowing for loopback testing, which we’ll discuss later in this chapter.

ADSL Using PPPoE over ATM

DSL is one of the more popular connection media for both companies and consumers because the local service is provided via a normal phone line with a DSL modem. This connection terminates at the telco digital subscriber line access multiplexer (DSLAM), a device that concentrates multiple DSL connections together. Some J-series routers have support for ATM over asymmetrical digital subscriber line (ADSL)—Annex A for DSL over POTS or Annex B for DSL over ISDN—and symmetric high-speed digital subscriber line (SHDSL) configurations that allow them to act as the DSL modem at the customer site. The interfaces appear to be ATM connections but do not support native ATM, only the use of ATM over a DSL connection.

Router PBR has an ADSL Annex A PIM installed in slot 6 and will act as a client to the DSLAM. This connection is using Point-to-Point Protocol over Ethernet (PPPoE) over ATM for the DSL connection, which requires that two different interfaces be configured. The first interface that is configured is the physical ATM interface of at-6/0/0 . To configure the interface, the ATM virtual path and virtual channel identities must be the same values that are provisioned at the DSLAM. The rest of the parameters can be learned from the DSLAM by setting an operating mode of auto. Since PBR will be using PPPoE, the encapsulation must be configured at both the physical and the logical layers:

The next interface that must be configured is the PPPoE internal router interface. This interface maps the physical interface where PPPoE will be running, sets the access server’s name and underlying service to be requested, and sets an IP address. The IP address can be learned automatically from the access server by specifying the negotiate-address command, as seen in the configuration of PBR that follows, or by setting the IP address to be static:

You can verify the correct operation of the PPPoE negotiation by issuing the show pppoe interfaces command:

To incrementally increase the speed of individual PPP links without adding speed to the physical interfaces, the Multilink Point-to-Point Protocol (MLPPP) was created under RFC 1990 . This is essentially a “software” bond of multiple physical PPP interfaces to form one larger logical link, called a bundle . Junos allows for up to eight physical interfaces to be assigned to a bundle.

To support MLPPP on any Juniper Networks router, the router must support this special service. This support could be in the form of an additional hardware PIC on an M-series router, or it could inherit software support on other Juniper routers.

The first step is to configure the pseudolink service interface, which takes the form of lsq-0/0/0 on J-series, MX, and SRX routers, or an ml , lsq , or ls interface on an M-series router, depending on the PIC type. This interface will take all the same characteristics of a normal PPP interface, such as an IP address, but will have a logical encapsulation of multilink-ppp . This is configured at the logical layer of the interface to allow multiple bundles and types of bundles on the same router by configuring multiple unit numbers. As shown here, the bundle is assigned to logical unit 0:

Next, configure the physical interfaces to link the newly created link service interface. In the following example, interfaces se-1/0/0 and se-1/0/1 are linked to the logical bundle unit 0 on the ls-0/0/0 interface:

To verify the status, issue the show interfaces terse command. Notice that both the serial interfaces and the link service interfaces are tracked. The link service will be in the up state as long as one of the physical interfaces is also in the up state. You can modify this by configuring the minimum-links number command under the link service interface. This command sets the number of physical links that must be in the up state for the bundle to be labeled up:

Notice the use of an “or” statement in the match criteria. The use of quotes and the pipe symbol denotes an or statement for the match, looking for lines that contain either se or lsq- .

Aggregated Ethernet

The IEEE 802.3ad standard defines a means to bundle multiple Ethernet interfaces into an aggregate group. Traffic is passed over all members of the group in a load-balancing arrangement. The link aggregation control protocol (LACP) can be added to monitor the bundle, allowing interfaces to be added or subtracted from the bundle without loss of traffic.

The use of 802.3ad allows multiple connections between a router and a switch without the possibility of a broadcast storm. This improves performance and has a quicker recovery time than using a spanning tree protocol.

The configuration of 802.3ad has three parts: setting the chassis parameters, the aggregate interface, and the participating interfaces. The chassis parameters define the total number of aggregate interfaces that will be set on the router. In this example, we are installing only a single aggregate interface:

The aggregate interface uses an internal interface type of ae0. This interface carries the logical interface properties for the interface—in this case, the IP address for the bundle:

Finally the participating interfaces are added to the configuration. Up to 10 Ethernet interfaces can be added to an aggregate bundle. These interfaces can be in any location on the router:

Once the configuration is entered and committed, the ae0 interface is monitored as any other interface on the router. The show interfaces ae0 command shows the interface’s bandwidth and status. The show interface terse command shows the addresses of the aggregate interface and the bundle of the aggregated Ethernet interfaces:

Generic Routing Encapsulation (GRE) is a tunneling protocol that enables the transport of a variety of Layer 3 protocols. The tunnel created by GRE was designed to be “stateless” with no monitoring of the tunnel endpoint. GRE tunnels are used for a variety of applications, including providing backup links, transporting non-IP protocols over an IP network, and connecting “islands” of IP networks.

To create a GRE tunnel on a Juniper Networks router, the router must be equipped with Layer 2 service capabilities, which are native in the J-series, MX, and SRX routers and are available via a hardware PIC in an M-series router. When these services are enabled on a router, a pseudointerface called gr is created. The interface must be configured with the source IP address for the GRE packets, the destination of the tunnel, and the families of protocols that will be carried in the protocol. The GRE tunnel configured in the following case is carrying IP traffic and is using a source IP address of and a destination of An IP address for the gr-0/0/0 interface is not required but could be useful for management purposes:

It is important not to mistake the internal gre interface with the gr interface on the router. The gre interface is used by the router internally and should not be configured to create GRE tunnels.

The final piece is mapping actual traffic for use by the GRE tunnel. This is accomplished in a variety of methods depending on the type of traffic entering the GRE tunnel. Common mapping examples for IP include creating a static route with a next-up of the gr interface or even running a routing protocol such as Open Shortest Path First (OSPF) over the interface!

Anybody using a PC for Internet surfing, music downloads, or gaming uses IP as the network protocol. The PC will have an IP address assigned as well as a default gateway address to reach any destinations that are not on the local subnet. In the following code snippet, a PC is using an IP address of with a mask of and a default gateway of

This default gateway address is either statically defined by the user or learned via the Dynamic Host Configuration Protocol (DHCP) process. Regardless of the method, the default gateway will be used as the next hop address for the default route that will be created to reach remote destinations:

If the default gateway was a single device and that device failed, a PC would not be able to reach destinations outside the local subnet. In a fault-tolerant network, it would be ideal to have a backup gateway device, without having to modify the configuration on the PC, as well as being able to load-share with multiple PCs on the LAN.

VRRP was created to eliminate single points of behavior that are inherent to static default routed networks. VRRP creates a logical grouping of multiple physical routers to a “virtual” router that will be used as the default gateway for end hosts. This allows the PC to always maintain the same gateway address even if the physical gateway has changed (see Figure 4-16 ). The routers that are part of the same VRRP logical group will share this “virtual” IP address as well as a “virtual” media access control (MAC) address. Essentially VRRP describes an election protocol to maintain ownership of this virtual IP (VIP) address and MAC address. One router in the VRRP group will be the master router, which controls this VIP address unless a failure occurs that results in a release of that ownership. This failure causes another router to claim ownership of the VIP by issuing a VRRP message and a gratuitous Address Resolution Protocol (ARP) to claim the virtual MAC address. Once a router becomes the master, it will periodically advertise VRRP messages to indicate its overall health and reachability.

When configuring VRRP for the first time on a Juniper Networks router, it can seem like locating the configuration is similar to trying to find a needle in a haystack. The configuration will be within the logical property and will be configured after the family inet address. A VRRP group value (1–255) is assigned on every router that needs to be part of the virtual router. Also, a VIP address is assigned that the hosts will use as their gateway address. This could be an address owned by one of the routers in the group or an address taken out of the address block owned by the LAN. Lastly, a priority value can be configured to change the default value of 100, which is used to elect the master router of the VRRP group. The router with the highest priority value becomes the master for that group; if the priorities are equal, the tiebreaker goes to the highest local LAN IP address:

VRRP example

Figure 4-16. VRRP example

Verify the operation of VRRP with the show vrrp summary command. Router Lager is the master for group 1 because it has a higher priority:

Priority values range from 0–255; however, only values 1–254 are configurable. Priority 0 is reserved for the master router to issue an immediate release of mastership. A priority of 255 is used if the VIP is an actual interface IP that is owned by that router.

Another option that can be configured is the ability to track the interface priority settings. If an interface goes down, the advertised priority will be subtracted by a configured value. This could result in a new master router for the virtual router. This is very useful to ensure upstream reachability. In the example on Lager , a T1 interface is being tracked. If this interface goes down, 150 will be subtracted from the configured priority of 200:

You can force an interface failure by administratively disabling the T1 interface:

The result of this failure is a mastership change, as Lager is now the backup router:

Notice in the show vrrp track command that Lager has a configured ( cfg ) priority value of 200, but a priority of 50 is currently being used because we’ve subtracted the cost of 150 from the downed T1 interface:

The default behavior of VRRP is to use preemption , which causes a router with a higher priority to become the master at any time. When Lager ’s T1 interface is reenabled, it will again become the master for the virtual router:

Since preemption could cause a temporary disruption in the network, a no-preempt command can also be configured.

Lastly, according to RFC 3768 , “A VRRP router SHOULD not forward packets addressed to the VIP Address(es) it becomes Master for if it is not the owner.” That means if we have an IP address that is not owned by any router and is simply an address from the subnet that was used as the VIP, operational issues may appear. The most common issue is not being able to ping the virtual address. In the case just examined, was the VIP address chosen out of the 10.40.1/24 subnet, but it was not actually configured on either Lager or Ale . Juniper routers allow you to break this rule by configuring the accept-data command to allow the master router to respond to the VIP address. This will allow testing to occur toward the VIP; however, care must be taken to avoid unnecessary traffic on the LAN.

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assign ip address to juniper interface

Network Encyclopedia

Basic configuration of a juniper router.

Basic Configuration of a Juniper Router

JUNOS Operational Mode

The JUNOS operating system has another option that enables the user to enter only part of a command. With this feature, the incomplete command will be completed by JUNOS if the user is still in the operational mode, indicated by the > prompt. This means the user doesn’t have to remember the full command. JUNOS will fill in the expected text given the information obtained from the entered keystrokes.

In this case, the router is running the Model: m10i software . The Juniper system is based on the UNIX OS platform . It has a Free BSD UNIX-based kernel with different software systems handling different functions. For example, this listing shows that there is a JUNOS routing software suite, a packet forwarding engine, a crypto software suite, and other software. This individual software suite setup allows one feature to be updated (for example, router updates) without having to update the entire router box.

PIC Physical interface card.

Router Configuration Mode

Displaying the router interfaces, hostname configuration, assigning an ip address to an interface, recent posts.

Juniper – Assign IP Address on switch

Fxp0: management interface 

To configure a management  port by CLI commands.

   Use the command “family inet address” to configure a management IP address on the interface.

  set interfaces me0 unit 0 family inet address

   Configure a static route with the next hop to the management network default gateway

set routing-options static route next-hop

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12. Junos Primary and Preferred Address

Junos Interface Initial Configuration includes configuring both physical properties and logical properties. IP address configuration is part of  interface logical configuration.

When you configure multiple IP addresses in Juniper devices, opposite to cisco devices, they are not replaced but all addresses will be added to the device.

Now the question is which address will be used as the source address when packets are originated from that interface. Junos Primary and Preferred address is the answer to this question.

Junos Primary Vs Preferred IP Address

Junos Initial Configuration of Ethernet Interface

Junos Primary and Preferred address

Junos interface configuration.

In Juniper devices, physical properties such as speed and duplex are configured in a different context than logical configurations such as IP address.

Junos Primary and Preferred Address

In Cisco devices, when you configure multiple IP addresses in one interface, you only see the latest IP address since it replaces the other IP addresses, unless you use the keyword “secondary” at the end of non-primary IP addresses.

But in juniper devices, by default all IP addresses are added to the interface unless you delete the old IP address.

when multiple IP addresses are configured, you have the option to select one of the IP addresses as primary and also one IP address as preferred.

What is the difference between Junos Primary and Preferred address?

Preferred address is used as the source address for packets originated from the interface.

Primary address is used as the source address for broadcast and multicast packets originated from this interface.

Junos Primary and Preferred address configuration

As previously explained, configuring physical interface properties such as speed and duplex requires you to enter the physical context.

As an example we enter “interfaces ge-0/0/0” to configure speed and duplex.

We configure duplex with “link-mode” option and speed with “speed” option.

And to configure IP address, you have to enter the logical context which is called “unit” in juniper devices.

In this context, it is possible to configure both IPV4 and IPV6 address. For IPV4 address, we choose “unit 0 family inet” and for IPv6 address configuration, we choose the option “unit 0 family inet6”.

As an example, I will give three IP address to the interface Ge-0/0/0, “”, “” as preferred address and “” as primary address.

You can make sure that all three IP address are maintained in the configuration and they are not replaced.

Just to be able to test, which IP address is used as the source address, I have to configure security zone options in SRX to generate traffic. we have not yet learned these concepts and you can also ignore the concept at this step.

If your device is not SRX firewall and it is just a router, then you do not need to configure security zone options. Actually you do not have any security zone option in the configuration.

After configuring security zones and gateway address, now we can test a ping connectivity to local subnet and also external subnet from the device itself to see which of these address are used as the source address.

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Juniper – How to add ip address vlan interface

assign ip address to juniper interface

I’m new to Juniper and it’s my first switch (EX-4200). In this article we will learn about how to add ip address vlan interface on Juniper switch EX series.

Associate a Layer 3 interface with the VLAN. Configure Layer 3 interfaces on trunk ports to allow the interface to transfer traffic between multiple VLANs. Within a VLAN, traffic is bridged, while across VLANs, traffic is routed.

Here is how to add IP address vlan interface on Juniper EX 4200, firmware version 12.4R:

1. Create layer2  vlan name and vlan id:

# set vlans vlan-name vlan-id vlan-id
# set vlans vlan100 vlan-id 100

2. Then assign that vlan to an interface:

# set interfaces interface-name unit logical-unit-number family ethernet-switching vlan members vlan-name
# set interfaces ge-0/0/7 unit 0 family ethernet-switching vlan members vlan100

3. Then create a logical l3 interface and assign that interface to a vlan:

# set interfaces vlan unit logical-unit-number family inet address inet-address
# set interfaces vlan unit 100 family inet address

4. The link l3-interface to a vlan:

# set vlans vlan-name l3-interface vlan.logical-interface-number
# set vlans vlan100 l3-interface vlan.100

Here is the result:

# run show interfaces vlan Physical interface: vlan, Enabled, Physical link is Up Interface index: 129, SNMP ifIndex: 328 Type: VLAN, Link-level type: VLAN, MTU: 1518, Speed: 1000mbps Device flags : Present Running Link type : Full-Duplex Link flags : None Current address: 00:23:9c:12:5b:00, Hardware address: 00:23:9c:12:5b:00 Last flapped : Never Input packets : 1808099 Output packets: 22785 Logical interface vlan.100 (Index 118) (SNMP ifIndex 630) Flags: SNMP-Traps 0x0 Encapsulation: ENET2 Input packets : 959 Output packets: 19 Protocol inet Flags: None Addresses, Flags: Is-Preferred Is-Primary Destination: 10.10.10/24, Local:, Broadcast:

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2 Replies to “ Juniper – How to add ip address vlan interface ”

Thank you. then after this config, any ports configured with VLAN100 should receive an IP of the range, right?

If you mean all devices connected to the vlan100 can get IP address automatically (DHCP), then the answer is no. To do the DHCP things, you must configure a DHCP server on vlan100.

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Juniper ® JNCIA Exam Cram Notes : Describe How To Configure Basic Components Of A Junos Device

4. Junos Configuration Basics

1. Configuring Hostname of the device: The hostname of a device is its identification. A router or switch must have its identity established to be accessible on the network to other devices. That is perhaps the most important reason to have a hostname, but a hostname has other purposes: Junos OS uses the configured hostname as part of the command prompt, to prepend log files and other accounting information, as well as in other places where knowing the device identity is useful. We recommend that the hostname be descriptive and memorable. We can configure the hostname at the [edit system] hierarchy level.

The following example configures hostname of router R1 as "juniper1"

step1 : Enter into configuration mode

[email protected]> configure [edit]

step 2 : Enter into system hierarchy mode

[email protected]# edit system [edit system]

step 3 : set the hostname as "juniper1"

[email protected]# set host-name juniper1 [edit system]


In Junos devices, 'set' command is used whenever we need to enter new information into the configuration.

2. Configure name-server on our juniper device: The command 'set system name-server' configures DNS servers to resolve hostnames, we use the set system name-server command.

[email protected]> configure [edit]

step 2 : Enter into System hierarchy mode

[email protected]# edit system [edit system]

step 3 : set the name server address as

[email protected]# set name-server [edit system]

3. Configuring Hold-down Timer: Hold-time value is used to damp interface transitions. When an interface goes from up to down, it is not advertised to the rest of the system as being down until it has remained down for the hold-time period. Similarly, an interface is not advertised as being up until it has remained up for the hold-time period.

step 2 : Move to so-0/0/0 interface hierarchy mode

[email protected]# edit interfaces so-0/0/0 [edit interfaces so-0/0/0]

step 3 : Set the holdtime value of 200 milliseconds to use when an interface transitions from down to up and holdtime value of 200 milliseconds to use when an interface transitions from up to down .

[email protected]# set hold-time up 200 down 200 [edit interfaces so-0/0/0]

4. We use 'delete' command to delete the configuration from our juniper devices . This command is used in configuration mode either to delete a particular configuration statement or completely delete the entire configuration. We use delete command to remove the variables from the configuration.

For example : [email protected] # delete system radius-server

The delete and deactivate are two different command that performs separate tasks. 'Delete' command deletes each and every configuration present on our junos devices. 'Deactivate' command doesn't delete the configuration but keeps the configuration into an inactive state.

Example: To delete the static route destined for address with a next-hop address The command is

delete routing-options static route next-hop

5. The command "load override common" , compares the results of the load override command with the common file that we saved earlier.

6. To configure encrypt password on router: Configuring the root password on your Junos OS-enabled router helps prevent unauthorized users from making changes to your network. The root user (also referred to as superuser) has unrestricted access and full permissions within the system, so it is crucial to protect these functions by setting a strong password when setting up a new router. After a new router is initially powered on, you log in as the user root with no password. Junos OS requires configuration of the root password before it accepts a commit operation. On a new device, the root password must always be a part of the configuration submitted with your initial commit.

step 2 : Move to the root-authentication hierarchy

[email protected]# edit system root-authentication [edit system root-authentication]

step 3 : Set the encrypted password as 24adr3e

[email protected]# set encrypted-password 24adr3e [edit system root-authentication]

7. Configure the device interface to shutdown state: By default, an interface will be in upstate. We need to issue disable command to bring-down the interface. We can disable a physical interface, marking it as being down, without removing the interface configuration statements from the configuration. To do this, include the disable statement at the [edit interfaces interface-name] hierarchy level

step 3 : Bring the so-0/0/0 to no shutdown state(disable)

[email protected]# set disable [edit interfaces so-0/0/0]

8. To configure ppp enacapsulation: When we configure a point-to-point encapsulation (such as PPP or Cisco HDLC) on a physical interface, the physical interface can have only one logical interface (that is, only one unit statement) associated with it. When you configure a multipoint encapsulation (such as Frame Relay), the physical interface can have multiple logical units, and the units can be either point-to-point or multipoint.

step 3 : set the encapsulation as ppp

[email protected]# set encapsulation ppp [edit interfaces so-0/0/0]

9. The juniper devices are powered off using "request system power-off" command. We must write this command staying on operational mode hierarchy

10. The command used to copy the JUNOS software into the hardware is 'request system snapshot' . To successfully boot the router from the hard drive, you first need to copy the JUNOS software and other critical files to it with the request system snapshot command.

The command used in juniper devices to commit our configuration for 30 minutes is 'commit confirmed 30'. This command makes our configuration active for 30 minutes.

11 The command used to set the generated route is: The 'set routing-options generate route' command on the configuration mode hierarchy helps us in configuring the generated routes on our junos device. Unlike static route, it doesn't have the next hop option

12 To configure the description of the interface

The description to an interface is set by using set description command

Step 1 : 1. Enter into configuration mode of R3

step 2 : Enter into so-0/0/0 interface configuration mode

step 3 : Set the description of interface so-0/0/0 as "interface-so-0/0/0"

[email protected]# set description "interface-so-0/0/0" [edit interfaces so-0/0/0]

13. Command syntax to configure IP address of a particular interface's: The 'set interfaces <interface-name> unit 0 family inet address <address>' command configures IPv4 address to a particular interface. This command is executed in configuration mode of Junos CLI.

Example: set interfaces ge-0/0/0 unit 0 family inet address  configures the ge-0/0/0 interface with ip address as

14. To configure Keepalive intervals

Syntax: keepalives <interval seconds> <down-count number> <up-count number>

Sending of keepalives is enabled by default. The default keepalive interval is 10 seconds for PPP, Frame Relay, or Cisco HDLC. The default down-count is 3 and the default up-count is 1 for PPP or Cisco HDLC.

step 3: Set keepalive interval as 40 ,down count as 30 and up count as 20 of interface so-0/0/0

[email protected]# set keepalives 40 30 20 [edit interfaces so-0/0/0]

Additional Initial Configuration elements:

NTP: The Network Time Protocol (NTP) is used to synchronize the time of a computer client or server to another server or reference time source. We enable NTP client or server within the [edit system ntp] hierarchy.

By default, network time synchronization is unauthenticated. The system will synchronize to whatever system appears to have the most accurate time. To authenticate other time servers, include the trusted-key statement at the [edit system ntp] hierarchy level. Only time servers transmitting network time packets that contain one of the specified key numbers and whose key matches the value configured for that key number are eligible to be synchronized to. Other options are not appropriate.

SNMP: By default, SNMP is disabled on devices running Junos OS. We must enable SNMP on our device by including configuration statements at the [edit snmp] hierarchy level. SNMP is Simple Network Management Protocol. By default, SNMP is disabled in juniper devices. We must enable it and configure it in '[edit snmp]' hierarchy in operational mode

Syslog: Syslog is a standard for computer message logging. It permits separation of the software that generates messages from the system that stores them and the software that reports and analyzes them. In juniper we configure it in [edit system syslog] hierarchy. Syslog messages on juniper devices can be seen using 'show log messages' command in operational mode hierarchy.

Juniper Configuration Hierarchy:

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