Routing Instance

Routing instances in Juniper routers provide powerful network segmentation capabilities, enabling administrators to create isolated routing and forwarding domains within a single physical router. This separation is crucial for maintaining security, preventing unauthorized resource usage, and organizing different types of network traffic.

Components of Routing Instances

Instance Types

Juniper supports four main types of routing instances, each designed for specific use cases:

1. Virtual Router

   • Maintains completely separate routing and forwarding tables

   • Provides full isolation between different routing domains

   • Ideal for multi-tenant environments

   • Configuration example:

   set routing-instances vr-customer instance-type virtual-router
   set routing-instances vr-customer interface ge-0/0/0.100
   set routing-instances vr-customer routing-options static route 192.168.1.0/24 next-hop 10.1.1.1

2. VRF (Virtual Routing and Forwarding)

   • Specifically designed for MPLS L3VPN services

   • Supports route distinguishers and route targets

   • Enables complex VPN topologies

   • Configuration example:

   set routing-instances vrf-customer instance-type vrf
   set routing-instances vrf-customer route-distinguisher 65000:1
   set routing-instances vrf-customer vrf-target target:65000:1
   set routing-instances vrf-customer interface ge-0/0/1.0

3. Forwarding

   • Shares a common routing table

   • Maintains separate forwarding tables

   • Useful for filter-based forwarding scenarios

   • Configuration example:

   set routing-instances fwd-instance instance-type forwarding
   set routing-instances fwd-instance routing-options instance-import fwd-import
   set routing-instances fwd-instance interface ge-0/0/2.0

4. Virtual Switch

   • Handles Layer 2 switching functionality

   • Supports VLAN-based segmentation

   • Ideal for campus or data center environments

   • Configuration example:

   set routing-instances vs-example instance-type virtual-switch
   set routing-instances vs-example bridge-domains bd-1 vlan-id 100
   set routing-instances vs-example interface ge-0/0/3.0

Route Import Configuration

Route import between instances requires careful policy configuration to maintain security and prevent unwanted route leaks:

1. Basic Import Policy

   set routing-options instance-import vr-sample-import
   
   set policy-options policy-statement vr-sample-import {
       term customer-routes {
           from {
               instance vr-customer;
               prefix-list customer-prefixes;
               route-filter 192.168.0.0/16 orlonger;
           }
           then {
               preference 150;
               tag 65000;
               accept;
           }
       }
       term deny-all {
           then reject;
       }
   }

2. RIB Groups for Route Sharing

   set routing-options rib-groups customer-to-master import-rib vr-customer.inet.0
   set routing-options rib-groups customer-to-master import-rib inet.0
   set routing-instances vr-customer routing-options interface-routes rib-group customer-to-master

3. Route Leaking Controls

   set routing-instances vr-customer routing-options autonomous-system 65000
   set routing-instances vr-customer protocols bgp group external-peers export leak-policy

Interface Assignment

Proper interface assignment is crucial for routing instance isolation:

1. Physical Interfaces

   set routing-instances vr-customer interface ge-0/0/0.100
   set routing-instances vr-customer interface ge-0/0/1.100

2. Logical Interfaces

   set routing-instances vr-customer interface lo0.1
   set routing-instances vr-customer interface irb.100

3. Aggregated Interfaces

   set routing-instances vr-customer interface ae0.0
   set routing-instances vr-customer interface ae1.0

Best Practices

Security Considerations

1. Policy Control

   • Always implement explicit deny statements

   • Use prefix-lists for route filtering

   • Implement proper route leaking controls

   • Example:

   set policy-options prefix-list customer-prefixes 192.168.0.0/16
   set policy-options prefix-list customer-prefixes 172.16.0.0/12

2. Interface Isolation

   • Maintain clear interface documentation

   • Use separate VLANs for different customers

   • Implement proper QoS policies

   • Example:

   set class-of-service interfaces ge-0/0/0 unit 100 forwarding-class assured-forwarding

Resource Management

1. Route Table Monitoring

   • Set appropriate route limits

   • Monitor table growth

   • Implement alerts for threshold violations

   • Example:

   set routing-instances vr-customer routing-options maximum-routes 10000 log-only

2. Memory Allocation

   • Monitor memory usage per instance

   • Set appropriate scaling parameters

   • Plan for growth

   • Example:

   set system memory-enhanced-mode

Verification Commands

1. Instance Status

   show route instance vr-customer detail
   show route instance vr-customer extensive

2. Route Tables

   show route table vr-customer.inet.0
   show route table vr-customer.inet.0 extensive

3. Interface Status

   show interfaces terse | match vr-customer
   show interfaces detail ge-0/0/0.100

4. Policy Verification

   show policy vr-sample-import detail
   show policy vr-sample-import extensive

5. Debug Commands

   show log messages | match vr-customer
   show system processes extensive | match routing