Setting an IP Address for the Router
Problem
You want to assign an address to the router itself so that you can reach it at all times, even when a particular interface is not available and so that applications such as SNMP can always reach the router.
Solution
Use the following command to configure a permanent address for the router:
[edit] aviva@RouterA# set interfaces lo0 unit 0 family inet address 192.168.16.1/32
Discussion
Most of the IP addresses you configure on a router are for physical network interfaces, such as an Ethernet or T1 interface. While these interfaces are generally present and operating in the router, you don't want to use them to find out the status of the router, because someone might remove the PIC from the router or because the physical interface may not be up or may not be configured properly even though the router is up and running fine. The solution is to configure an IP address that uniquely identifies your router. You do this by configuring the lo0, or loopback, address.
In the JUNOS software, the loopback address is named lo0. This name doesn't follow the standard JUNOS interface naming conventions. It is just the same name as the Unix loopback interface. You don't need to specify a PIC, FPC, or slot number because the loopback address is not associated with hardware, but is just an internal address on the router. You configure the loopback address on logical unit 0, and the address is an IPv4 address (set with the keyword inet). In this recipe, we set the loopback address to 192.168.16.1/32.
The loopback address on a JUNOS router is used as the IP address of the router itself and is similar to the Unix localhost, which is the address of the local system. The JUNOS software uses this address when it needs to talk to itself using IP.
To see that the loopback address has been configured, you can look at its status:
aviva@RouterA> show interfaces lo0 Physical interface: lo0, Enabled, Physical link is Up Interface index: 6, SNMP ifIndex: 6 Type: Loopback, MTU: Unlimited Device flags : Present Running Loopback Interface flags: SNMP-Traps Link flags : None Last flapped : Never Input packets : 19 Output packets: 19 Logical interface lo0.0 (Index 69) (SNMP ifIndex 16) Flags: SNMP-Traps Encapsulation: Unspecified Input packets : 0 Output packets: 0 Protocol inet, MTU: Unlimited Flags: None Addresses, Flags: Is-Default Is-Primary Local: 192.168.16.1 Logical interface lo0.16385 (Index 64) (SNMP ifIndex 21) Flags: SNMP-Traps Encapsulation: Unspecified Input packets : 5 Output packets: 5 Protocol inet, MTU: Unlimited Flags: None Addresses, Flags: Is-Default Is-Primary Local: 10.0.0.1 Addresses Local: 10.0.0.16
You see the loopback interface address in the logical interface portion of the output. You can see that the lo0 interface is operational (from the Present and Running device flags) and that it is a loopback interface (from the Loopback device flag) with an unlimited MTU size. SNMP traps are enabled on the router, no link flags are set (these flags are only for network interfaces, which lo0 is not), and the interface has never gone down and come back up (flapped). The input and output fields show the number of packets that have passed through the interface. One interesting thing to notice is the existence of logical interface lo0.16385. This is a nonconfigurable interface created by the JUNOS software for routing platform control traffic. The two addresses shown for this logical interface are used internally.
Because the address is just an address for the router and is not used for a software loopback mechanism, it can be any /32 address. You are not limited to using the standard loopback address of 127.0.0.1. Some JUNOS applications, including NTP, RADIUS, TACACS+, and SSL for the JUNOScript API, require a loopback address of 127.0.0.1. You either can set this as your primary loopback address or can configure multiple loopback addresses:
[edit] aviva@RouterA# set interfaces lo0 unit 0 family inet address 192.168.16.1/32 aviva@RouterA# set interfaces lo0 unit 0 family inet address 127.0.0.1/32
You see that this address is configured, but is not the default or primary address:
aviva@RouterA# run show interfaces lo0.0 Logical interface lo0.0 (Index 69) (SNMP ifIndex 16) Flags: SNMP-Traps Encapsulation: Unspecified Input packets : 0 Output packets: 0 Protocol inet, MTU: Unlimited Flags: None Addresses Local: 127.0.0.1 Addresses, Flags: Is-Default Is-Primary Local: 192.168.42.1
See Also
Recipes 7.1 and 7.10
Router Configuration and File Management
- Introduction
- Configuring the Router for the First Time
- Configuring the Router from the CLI
- Getting Exclusive Access to Configure the Router
- Displaying the Commands to Recreate a Configuration
- Including Comments in the Configuration
- Checking the Syntax of the Configuration
- Activating the Router Configuration
- Debugging a Failed Commit
- Exiting Configuration Mode
- Keeping a Record of Configuration Changes
- Determining What Changes You Have Made to the Configuration
- Configuring the Router by Copying a File from a Server
- Configuring the Router by Copying Text from a Terminal Window
- Backing Up the Routers Configuration
- Scheduling the Activation of a Configuration
- Provisionally Activating a Configuration
- Loading a Previous Router Configuration
- Creating an Emergency Rescue Configuration
- Backing Up Filesystems on M-Series and T-Series Routers
- Backing Up Filesystems on J-Series Routers
- Restoring a Backed-Up Filesystem
- Installing a Different Software Release on M-Series and T-Series Routers
- Installing a Different Software Release on J-Series Routers
- Creating an Emergency Boot Disk
- Gathering Software Version Information
- Gathering Hardware Inventory Information
- Finding Out How Long the Router Has Been Up
- Gathering Information Before Contacting Support
- Managing Routers with Similar Configurations
- Managing Redundant Routing Engines
- Using the Second Routing Engine to Upgrade to a New Software Version
Basic Router Security and Access Control
- Basic Router Security and Access Control
- Introduction
- Allowing Access to the Router
- Controlling Root Authentication
- Logging In to the Routers Console
- Setting the Login Authentication Methods
- Setting Up Login Accounts on the Router
- Changing the Format of Plain-Text Passwords
- Changing the Plain-Text Password Encryption Method
- Creating a Login Account for Remote Authentication
- Creating a Group Login Account
- Customizing Account Privileges
- Creating a Privilege Class that Hides Encrypted Passwords
- Setting Up RADIUS User Authentication
- Setting Up TACACS+ User Authentication
- Restricting Inbound SSH and Telnet Access
- Setting the Source Address for Telnet Connections
- Creating a Login Banner
- Finding Out Who Is Logged In to the Router
- Logging Out of the Router
- Forcibly Logging a User Out
IPSec
- IPSec
- Introduction
- Configuring IPSec
- Configuring IPSec Dynamic SAs
- Creating IPSec Dynamic SAs on J-Series Routers or Routers with AS PICs
- Using Digital Certificates to Create Dynamic IPSec SAs
SNMP
- SNMP
- Introduction
- Configuring SNMP
- Setting Router Information for the MIB-II System Group
- Setting Up SNMP Traps
- Controlling SNMP Access to the Router
- Using a Firewall Filter to Protect SNMP Access
- Controlling Access to Router MIBs
- Extracting Software Inventory Information with SNMP
- Extracting Hardware Inventory Information with SNMP
- Collecting Router Operational Information with SNMP
- Logging SNMP Access to the Router
- Logging Enterprise-Specific Traps
- Using RMON Traps to Monitor the Routers Temperature
- Configuring SNMPv3
- Tracking Router Configuration Changes
- Setting Up SNMPv3 Traps
Logging
- Logging
- Introduction
- Turning On Logging
- Limiting the Messages Collected
- Including the Facility and Severity in Messages
- Changing the Size of a Logging File
- Clearing the Routers Logfiles
- Sending Log Messages to Your Screen
- Sending Logging Messages to a Log Server
- Saving Logging Messages to the Other Routing Engine
- Turning Off Logging
- Turning On Basic Tracing
- Monitoring Interface Traffic
NTP
- NTP
- Introduction
- Setting the Date and Time on the Router Manually
- Setting the Time Zone
- Synchronizing Time When the Router Boots
- Synchronizing Time Periodically
- Authenticating NTP
- Checking NTP Status
Router Interfaces
- Router Interfaces
- Introduction
- Viewing Interface Status
- Viewing Traffic Statistics on an Interface
- Setting an IP Address for the Router
- Setting the Routers Source Address
- Configuring an IPv4 Address on an Interface
- Configuring an IPv6 Address on an Interface
- Configuring an ISO Address on an Interface
- Creating an MPLS Protocol Family on a Logical Interface
- Configuring an Interface Description
- Choosing Primary and Preferred Interface Addresses
- Using the Management Interface
- Finding Out What IP Addresses Are Used on the Router
- Configuring Ethernet Interfaces
- Using VRRP on Ethernet Interfaces
- Connecting to an Ethernet Switch
- Configuring T1 Interfaces
- Performing a Loopback Test on a T1 Interface
- Setting Up a BERT Test on a T1 Interface
- Configuring Frame Relay on a T1 Interface
- Configuring a SONET Interface
- Using APS to Protect Against SONET Circuit Failures
- Configuring an ATM Interface
- Dealing with Nonconfigurable Interfaces
- Configuring Interfaces Before the PICs Are Installed
IP Routing
- IP Routing
- Introduction
- Viewing the Routes in the Routing Table
- Viewing Routes to a Particular Prefix
- Viewing Routes Learned from a Specific Protocol
- Displaying the Routes in the Forwarding Table
- Creating Static Routes
- Blackholing Routes
- Filtering Traffic Using Unicast Reverse-Path Forwarding
- Aggregating Routes
- Load-Balancing Traffic Flows
- Adding Martian Addresses
- Changing Route Preferences to Migrate to Another IGP
- Configuring Routing Protocols to Restart Without Losing Adjacencies
Routing Policy and Firewall Filters
- Routing Policy and Firewall Filters
- Introduction
- Creating a Simple Routing Policy
- Changing a Routes Routing Information
- Filtering Routes by IP Address
- Filtering Long Prefixes
- Filtering Unallocated Prefix Blocks
- Creating a Chain of Routing Policies
- Making Sure a Routing Policy Is Functioning Properly
- Creating a Simple Firewall Filter that Matches Packet Contents
- Creating a Firewall Filter that Negates a Match
- Reordering Firewall Terms
- Filtering Traffic Transiting the Router
- Using a Firewall Filter to Count Traffic on an Interface
- Logging the Traffic on an Interface
- Limiting Traffic on an Interface
- Protecting the Local Routing Engine
- Rate-Limiting Traffic Flow to the Routing Engine
- Using Counters to Determine Whether a Router Is Under Attack
RIP
- RIP
- Introduction
- Configuring RIP
- Having RIP Advertise Its Routes
- Configuring RIP for IPv6
- Enabling RIP Authentication
- Routing RIP Traffic over Faster Interfaces
- Sending Version 1 Update Messages
- Tracing RIP Protocol Traffic
IS-IS
- IS-IS
- Introduction
- Configuring IS-IS
- Viewing the IS-IS Link-State Database
- Viewing Routes Learned by IS-IS
- Configuring IS-IS for IPv6
- Configuring a Level 1Only Router
- Controlling DIS Election
- Enabling IS-IS Authentication
- Redistributing Static Routes into IS-IS
- Leaking IS-IS Level 2 Routes into Level 1
- Adjusting IS-IS Link Costs
- Improving IS-IS Convergence Times
- Moving IS-IS Traffic off a Router
- Disabling IS-IS on an Interface
- Tracing IS-IS Protocol Traffic
OSPF
- Introduction
- Configuring OSPF
- Viewing Routes Learned by OSPF
- Viewing the OSPF Link-State Database
- Configuring OSPF for IPv6
- Configuring a Multiarea OSPF Network
- Setting Up Stub Areas
- Creating a Not-So-Stubby Area
- Summarizing Routes in OSPF
- Enabling OSPF Authentication
- Redistributing Static Routes into OSPF
- Adjusting OSPF Link Costs
- Improving OSPF Convergence Times
- Moving OSPF Traffic off a Router
- Disabling OSPF on an Interface
- Tracing OSPF Protocol Traffic
BGP
- Introduction
- Configuring a BGP Session Between Routers in Two ASs
- Configuring BGP on Routers Within an AS
- Diagnosing TCP Session Problems
- Adjusting the Next-Hop Attribute
- Adjusting Local Preference Values
- Removing Private AS Numbers from the AS Path
- Prepending AS Numbers to the AS Path
- Filtering BGP Routes Based on AS Paths
- Restricting the Number of Routes Advertised to a BGP Peer
- Authenticating BGP Peers
- Setting Up Route Reflectors
- Mitigating Route Instabilities with Route Flap Damping
- Adding a BGP Community to Routes
- Load-Balancing BGP Traffic
- Tracing BGP Protocol Traffic
MPLS
- Introduction
- Configuring LSPs Using LDP as the Signaling Protocol
- Viewing Information and LDP-Signaled LSPs in the Routing Tables
- Verifying that an LDP-Signaled LSP Is Carrying Traffic
- Enabling LDP Authentication
- Tracing LDP Operations
- Setting Up RSVP-Signaled LSPs
- Viewing Information About RSVP-Signaled LSPs in the Routing Tables
- Verifying Packet Labels
- Verifying that the RSVP-Signaled LSP Is Carrying Traffic
- Configuring RSVP Authentication
- Protecting an LSPs Path
- Using Fast Reroute to Reduce Packet Loss Following a Link Failure
- Automatically Allocating Bandwidth
- Prioritizing LSPs
- Allowing IGP Traffic to Use an LSP
- Installing LSPs into the Unicast Routing Table
- Tracing RSVP Operations
VPNs
- Introduction
- Setting Up a Simple Layer 3 VPN
- Viewing the VPN Routing Tables
- Adding a VPN for a Second Customer
IP Multicast
- Introduction
- Configuring PIM-SM
- Manually Establishing a PIM-SM RP
- Using Auto-RP to Dynamically Map RPs
- Setting Up a PIM-SM Bootstrap Router
- Filtering PIM-SM Bootstrap Messages
- Configuring Multiple RPs in a PIM-SM Domain with Anycast RP
- Configuring Multiple RPs in a PIM-SM Domain Anycast PIM
- Limiting the Group Ranges an RP Services
- Viewing Multicast Routes
- Checking the Groups for Which a PIM-SM Router Maintains Join State
- Manually Configuring IGMP
- Using SSM
- Connecting PIM-SM Domains Using MSDP and MBGP
- Configuring PIM-DM
- Tracing PIM Packets
EAN: 2147483647
Pages: 290
