- play_arrow Configuring Firewall Filters
- play_arrow Understanding How Firewall Filters Protect Your Network
- Firewall Filters Overview
- Router Data Flow Overview
- Stateless Firewall Filter Overview
- Understanding How to Use Standard Firewall Filters
- Understanding How Firewall Filters Control Packet Flows
- Stateless Firewall Filter Components
- Stateless Firewall Filter Application Points
- How Standard Firewall Filters Evaluate Packets
- Understanding Firewall Filter Fast Lookup Filter
- Understanding Egress Firewall Filters with PVLANs
- Selective Class-based Filtering on PTX Routers
- Guidelines for Configuring Firewall Filters
- Guidelines for Applying Standard Firewall Filters
- Supported Standards for Filtering
- Monitoring Firewall Filter Traffic
- Troubleshooting Firewall Filters
- play_arrow Firewall Filter Match Conditions and Actions
- Overview of Firewall Filters (OCX Series)
- Overview of Firewall Filter Profiles on ACX Series Routers (Junos OS Evolved)
- Understanding Firewall Filter Match Conditions
- Understanding Firewall Filter Planning
- Understanding How Firewall Filters Are Evaluated
- Understanding Firewall Filter Match Conditions
- Firewall Filter Flexible Match Conditions
- Firewall Filter Nonterminating Actions
- Firewall Filter Terminating Actions
- Firewall Filter Match Conditions and Actions (ACX Series Routers)
- Firewall Filter Match Conditions and Actions in ACX Series Routers (Junos OS Evolved)
- Firewall Filter Match Conditions for Protocol-Independent Traffic
- Firewall Filter Match Conditions for IPv4 Traffic
- Firewall Filter Match Conditions for IPv6 Traffic
- Firewall Filter Match Conditions Based on Numbers or Text Aliases
- Firewall Filter Match Conditions Based on Bit-Field Values
- Firewall Filter Match Conditions Based on Address Fields
- Firewall Filter Match Conditions Based on Address Classes
- Understanding IP-Based Filtering and Selective Port Mirroring of MPLS Traffic
- Firewall Filter Match Conditions for MPLS Traffic
- Firewall Filter Match Conditions for MPLS-Tagged IPv4 or IPv6 Traffic
- Firewall Filter Match Conditions for VPLS Traffic
- Firewall Filter Match Conditions for Layer 2 CCC Traffic
- Firewall Filter Match Conditions for Layer 2 Bridging Traffic
- Firewall Filter Support on Loopback Interface
- play_arrow Applying Firewall Filters to Routing Engine Traffic
- Configuring Logical Units on the Loopback Interface for Routing Instances in Layer 3 VPNs
- Example: Configuring a Filter to Limit TCP Access to a Port Based On a Prefix List
- Example: Configuring a Stateless Firewall Filter to Accept Traffic from Trusted Sources
- Example: Configure a Filter to Block Telnet and SSH Access
- Example: Configuring a Filter to Block TFTP Access
- Example: Configuring a Filter to Accept Packets Based on IPv6 TCP Flags
- Example: Configuring a Filter to Block TCP Access to a Port Except from Specified BGP Peers
- Example: Configuring a Stateless Firewall Filter to Protect Against TCP and ICMP Floods
- Example: Protecting the Routing Engine with a Packets-Per-Second Rate Limiting Filter
- Example: Configuring a Filter to Exclude DHCPv6 and ICMPv6 Control Traffic for LAC Subscriber
- Port Number Requirements for DHCP Firewall Filters
- Example: Configuring a DHCP Firewall Filter to Protect the Routing Engine
- play_arrow Applying Firewall Filters to Transit Traffic
- Example: Configuring a Filter for Use as an Ingress Queuing Filter
- Example: Configuring a Filter to Match on IPv6 Flags
- Example: Configuring a Filter to Match on Port and Protocol Fields
- Example: Configuring a Filter to Count Accepted and Rejected Packets
- Example: Configuring a Filter to Count and Discard IP Options Packets
- Example: Configuring a Filter to Count IP Options Packets
- Example: Configuring a Filter to Count and Sample Accepted Packets
- Example: Configuring a Filter to Set the DSCP Bit to Zero
- Example: Configuring a Filter to Set the DSCP Bit to Zero
- Example: Configuring a Filter to Match on Two Unrelated Criteria
- Example: Configuring a Filter to Accept DHCP Packets Based on Address
- Example: Configuring a Filter to Accept OSPF Packets from a Prefix
- Example: Configuring a Stateless Firewall Filter to Handle Fragments
- Configuring a Firewall Filter to Prevent or Allow IPv4 Packet Fragmentation
- Configuring a Firewall Filter to Discard Ingress IPv6 Packets with a Mobility Extension Header
- Example: Configuring an Egress Filter Based on IPv6 Source or Destination IP Addresses
- Example: Configuring a Rate-Limiting Filter Based on Destination Class
- play_arrow Configuring Firewall Filters in Logical Systems
- Firewall Filters in Logical Systems Overview
- Guidelines for Configuring and Applying Firewall Filters in Logical Systems
- References from a Firewall Filter in a Logical System to Subordinate Objects
- References from a Firewall Filter in a Logical System to Nonfirewall Objects
- References from a Nonfirewall Object in a Logical System to a Firewall Filter
- Example: Configuring Filter-Based Forwarding
- Example: Configuring Filter-Based Forwarding on Logical Systems
- Example: Configuring a Stateless Firewall Filter to Protect a Logical System Against ICMP Floods
- Example: Configuring a Stateless Firewall Filter to Protect a Logical System Against ICMP Floods
- Unsupported Firewall Filter Statements for Logical Systems
- Unsupported Actions for Firewall Filters in Logical Systems
- Filter-Based Forwarding for Routing Instances
- Forwarding Table Filters for Routing Instances on ACX Series Routers
- Configuring Forwarding Table Filters
- play_arrow Configuring Firewall Filter Accounting and Logging
- play_arrow Attaching Multiple Firewall Filters to a Single Interface
- Applying Firewall Filters to Interfaces
- Configuring Firewall Filters
- Multifield Classifier Example: Configuring Multifield Classification
- Multifield Classifier for Ingress Queuing on MX Series Routers with MPC
- Assigning Multifield Classifiers in Firewall Filters to Specify Packet-Forwarding Behavior (CLI Procedure)
- Understanding Multiple Firewall Filters in a Nested Configuration
- Guidelines for Nesting References to Multiple Firewall Filters
- Understanding Multiple Firewall Filters Applied as a List
- Guidelines for Applying Multiple Firewall Filters as a List
- Example: Applying Lists of Multiple Firewall Filters
- Example: Nesting References to Multiple Firewall Filters
- Example: Filtering Packets Received on an Interface Set
- play_arrow Attaching a Single Firewall Filter to Multiple Interfaces
- Interface-Specific Firewall Filter Instances Overview
- Interface-Specific Firewall Filter Instances Overview
- Filtering Packets Received on a Set of Interface Groups Overview
- Filtering Packets Received on an Interface Set Overview
- Example: Configuring Interface-Specific Firewall Filter Counters
- Example: Configuring a Stateless Firewall Filter on an Interface Group
- play_arrow Configuring Filter-Based Tunneling Across IP Networks
- Understanding Filter-Based Tunneling Across IPv4 Networks
- Firewall Filter-Based L2TP Tunneling in IPv4 Networks Overview
- Interfaces That Support Filter-Based Tunneling Across IPv4 Networks
- Components of Filter-Based Tunneling Across IPv4 Networks
- Example: Transporting IPv6 Traffic Across IPv4 Using Filter-Based Tunneling
- play_arrow Configuring Service Filters
- Service Filter Overview
- How Service Filters Evaluate Packets
- Guidelines for Configuring Service Filters
- Guidelines for Applying Service Filters
- Example: Configuring and Applying Service Filters
- Service Filter Match Conditions for IPv4 or IPv6 Traffic
- Service Filter Nonterminating Actions
- Service Filter Terminating Actions
- play_arrow Configuring Simple Filters
- play_arrow Configuring Layer 2 Firewall Filters
- Understanding Firewall Filters Used to Control Traffic Within Bridge Domains and VPLS Instances
- Example: Configuring Filtering of Frames by MAC Address
- Example: Configuring Filtering of Frames by IEEE 802.1p Bits
- Example: Configuring Filtering of Frames by Packet Loss Priority
- Example: Configuring Policing and Marking of Traffic Entering a VPLS Core
- Understanding Firewall Filters on OVSDB-Managed Interfaces
- Example: Applying a Firewall Filter to OVSDB-Managed Interfaces
- play_arrow Configuring Firewall Filters for Forwarding, Fragments, and Policing
- Filter-Based Forwarding Overview
- Firewall Filters That Handle Fragmented Packets Overview
- Stateless Firewall Filters That Reference Policers Overview
- Example: Configuring Filter-Based Forwarding on the Source Address
- Example: Configuring Filter-Based Forwarding to a Specific Outgoing Interface or Destination IP Address
- play_arrow Configuring Firewall Filters (EX Series Switches)
- Firewall Filters for EX Series Switches Overview
- Understanding Planning of Firewall Filters
- Understanding Firewall Filter Match Conditions
- Understanding How Firewall Filters Control Packet Flows
- Understanding How Firewall Filters Are Evaluated
- Understanding Firewall Filter Processing Points for Bridged and Routed Packets on EX Series Switches
- Firewall Filter Match Conditions, Actions, and Action Modifiers for EX Series Switches
- Platform Support for Firewall Filter Match Conditions, Actions, and Action Modifiers on EX Series Switches
- Support for Match Conditions and Actions for Loopback Firewall Filters on Switches
- Configuring Firewall Filters (CLI Procedure)
- Understanding How Firewall Filters Test a Packet's Protocol
- Understanding Filter-Based Forwarding for EX Series Switches
- Example: Configuring Firewall Filters for Port, VLAN, and Router Traffic on EX Series Switches
- Example: Configuring a Firewall Filter on a Management Interface on an EX Series Switch
- Example: Using Filter-Based Forwarding to Route Application Traffic to a Security Device
- Example: Applying Firewall Filters to Multiple Supplicants on Interfaces Enabled for 802.1X or MAC RADIUS Authentication
- Verifying That Policers Are Operational
- Troubleshooting Firewall Filters
- play_arrow Configuring Firewall Filters (QFX Series Switches, EX4600 Switches, PTX Series Routers)
- Overview of Firewall Filters (QFX Series)
- Understanding Firewall Filter Planning
- Planning the Number of Firewall Filters to Create
- Firewall Filter Match Conditions and Actions (QFX and EX Series Switches)
- Firewall Filter Match Conditions and Actions (QFX10000 Switches)
- Firewall Filter Match Conditions and Actions (PTX Series Routers)
- Firewall and Policing Differences Between PTX Series Packet Transport Routers and T Series Matrix Routers
- Configuring Firewall Filters
- Applying Firewall Filters to Interfaces
- Overview of MPLS Firewall Filters on Loopback Interface
- Configuring MPLS Firewall Filters and Policers on Switches
- Configuring MPLS Firewall Filters and Policers on Routers
- Configuring MPLS Firewall Filters and Policers
- Understanding How a Firewall Filter Tests a Protocol
- Understanding Firewall Filter Processing Points for Bridged and Routed Packets
- Understanding Filter-Based Forwarding
- Example: Using Filter-Based Forwarding to Route Application Traffic to a Security Device
- Configuring a Firewall Filter to De-Encapsulate GRE or IPIP Traffic
- Verifying That Firewall Filters Are Operational
- Monitoring Firewall Filter Traffic
- Troubleshooting Firewall Filter Configuration
- play_arrow Configuring Firewall Filter Accounting and Logging (EX9200 Switches)
-
- play_arrow Configuring Traffic Policers
- play_arrow Understanding Traffic Policers
- Policer Implementation Overview
- ARP Policer Overview
- Example: Configuring ARP Policer
- Understanding the Benefits of Policers and Token Bucket Algorithms
- Determining Proper Burst Size for Traffic Policers
- Controlling Network Access Using Traffic Policing Overview
- Traffic Policer Types
- Order of Policer and Firewall Filter Operations
- Understanding the Frame Length for Policing Packets
- Supported Standards for Policing
- Hierarchical Policer Configuration Overview
- Understanding Enhanced Hierarchical Policers
- Packets-Per-Second (pps)-Based Policer Overview
- Guidelines for Applying Traffic Policers
- Policer Support for Aggregated Ethernet Interfaces Overview
- Example: Configuring a Physical Interface Policer for Aggregate Traffic at a Physical Interface
- Firewall and Policing Differences Between PTX Series Packet Transport Routers and T Series Matrix Routers
- Hierarchical Policers on ACX Series Routers Overview
- Guidelines for Configuring Hierarchical Policers on ACX Series Routers
- Hierarchical Policer Modes on ACX Series Routers
- Processing of Hierarchical Policers on ACX Series Routers
- Actions Performed for Hierarchical Policers on ACX Series Routers
- Configuring Aggregate Parent and Child Policers on ACX Series Routers
- play_arrow Configuring Policer Rate Limits and Actions
- play_arrow Configuring Layer 2 Policers
- Hierarchical Policers
- Configuring a Policer Overhead
- Two-Color and Three-Color Policers at Layer 2
- Layer 2 Traffic Policing at the Pseudowire Overview
- Configuring a Two-Color Layer 2 Policer for the Pseudowire
- Configuring a Three-Color Layer 2 Policer for the Pseudowire
- Applying the Policers to Dynamic Profile Interfaces
- Attaching Dynamic Profiles to Routing Instances
- Using Variables for Layer 2 Traffic Policing at the Pseudowire Overview
- Configuring a Policer for the Complex Configuration
- Creating a Dynamic Profile for the Complex Configuration
- Attaching Dynamic Profiles to Routing Instances for the Complex Configuration
- Verifying Layer 2 Traffic Policers on VPLS Connections
- Understanding Policers on OVSDB-Managed Interfaces
- Example: Applying a Policer to OVSDB-Managed Interfaces
- play_arrow Configuring Two-Color and Three-Color Traffic Policers at Layer 3
- Two-Color Policer Configuration Overview
- Basic Single-Rate Two-Color Policers
- Bandwidth Policers
- Prefix-Specific Counting and Policing Actions
- Policer Overhead to Account for Rate Shaping in the Traffic Manager
- Three-Color Policer Configuration Overview
- Applying Policers
- Three-Color Policer Configuration Guidelines
- Basic Single-Rate Three-Color Policers
- Basic Two-Rate Three-Color Policers
- Example: Configuring a Two-Rate Three-Color Policer
- play_arrow Configuring Logical and Physical Interface Traffic Policers at Layer 3
- play_arrow Configuring Policers on Switches
- Overview of Policers
- Traffic Policer Types
- Understanding the Use of Policers in Firewall Filters
- Understanding Tricolor Marking Architecture
- Configuring Policers to Control Traffic Rates (CLI Procedure)
- Configuring Tricolor Marking Policers
- Understanding Policers with Link Aggregation Groups
- Understanding Color-Blind Mode for Single-Rate Tricolor Marking
- Understanding Color-Aware Mode for Single-Rate Tricolor Marking
- Understanding Color-Blind Mode for Two-Rate Tricolor Marking
- Understanding Color-Aware Mode for Two-Rate Tricolor Marking
- Example: Using Two-Color Policers and Prefix Lists
- Example: Using Policers to Manage Oversubscription
- Assigning Forwarding Classes and Loss Priority
- Configuring Color-Blind Egress Policers for Medium-Low PLP
- Configuring Two-Color and Three-Color Policers to Control Traffic Rates
- Verifying That Two-Color Policers Are Operational
- Verifying That Three-Color Policers Are Operational
- Troubleshooting Policer Configuration
- Troubleshooting Policer Configuration
-
- play_arrow Configuration Statements and Operational Commands
- play_arrow Troubleshooting
- play_arrow Knowledge Base
-
ON THIS PAGE
Example: Configuring a Routing Policy to Advertise the Best External Route to Internal Peers
The BGP protocol specification, as defined in RFC 1771, specifies that a BGP peer shall advertise to its internal peers the higher preference external path, even if this path is not the overall best (in other words, even if the best path is an internal path). In practice, deployed BGP implementations do not follow this rule. The reasons for deviating from the specification are as follows:
Minimizing the amount of advertised information. BGP scales according to the number of available paths.
Avoiding routing and forwarding loops.
There are, however, several scenarios in which the behavior, specified in RFC 1771, of advertising the best external route might be beneficial. Limiting path information is not always desirable as path diversity might help reduce restoration times. Advertising the best external path can also address internal BGP (IBGP) route oscillation issues as described in RFC 3345, Border Gateway Protocol (BGP) Persistent Route Oscillation Condition.
The advertise-external statement modifies the behavior
of a BGP speaker to advertise the best external path to IBGP peers,
even when the best overall path is an internal path.
The advertise-external statement is supported
at both the group and neighbor level. If you configure the statement
at the neighbor level, you must configure it for all neighbors in
a group. Otherwise, the group is automatically split into different
groups.
The conditional option limits the behavior of the advertise-external setting, such that the external route is
advertised only if the route selection process reaches the point where
the multiple exit discriminator (MED) metric is evaluated. Thus, an
external route is not advertised if it has, for instance, an AS path
that is worse (longer) than that of the active path. The conditional option restricts external path advertisement to when the best external
path and the active path are equal until the MED step of the route
selection process. Note that the criteria used for selecting the best
external path is the same whether or not the conditional option is configured.
Junos OS also provides support for configuring a BGP export policy that matches the state of an advertised route. You can match either active or inactive routes, as follows:
policy-options {
policy-statement name{
from state (active|inactive);
}
}
This qualifier only matches when used in the context of an export
policy. When a route is being advertised by a protocol that can advertise
inactive routes (such as BGP), state inactive matches routes
advertised as a result of the advertise-inactive and advertise-external statements.
For example, the following configuration can be used
as a BGP export policy toward internal peers to mark routes advertised
due to the advertise-external setting with a user-defined
community. That community can be later used by the receiving routers
to filter out such routes from the forwarding table. Such a mechanism
can be used to address concerns that advertising paths not used for
forwarding by the sender might lead to forwarding loops.
user@host# show policy-options
policy-statement mark-inactive {
term inactive {
from state inactive;
then {
community set comm-inactive;
}
}
term default {
from protocol bgp;
then accept;
}
then reject;
}
community comm-inactive members 65536:65284;
Overview
This example shows three routing devices. Device R2 has an external BGP (EBGP) connection to Device R1. Device R2 has an IBGP connection to Device R3.
Device R1 advertises 172.16.6.0/24. Device R2 does not set the local preference in an import policy for Device R1’s routes, and thus 172.16.6.0/24 has the default local preference of 100.
Device R3 advertises 172.16.6.0/24 with a local preference of 200.
When the advertise-external statement is not configured
on Device R2, 172.16.6.0/24 is not advertised by Device R2 toward
Device R3.
When the advertise-external statement is configured
on Device R2 on the session toward Device R3, 172.16.6.0/24 is advertised
by Device R2 toward Device R3.
When advertise-external conditional is configured
on Device R2 on the session toward Device R3, 172.16.6.0/24 is not
advertised by Device R2 toward Device R3. If you remove the then
local-preference 200 setting on Device R3 and add the path-selection
as-path-ignore setting on Device R2 (thus making the path selection
criteria equal until the MED step of the route selection process),
172.16.6.0/24 is advertised by Device R2 toward Device R3.
To configure the advertise-external statement
on a route reflector, you must disable intracluster reflection with
the no-client-reflect statement, and the client cluster must be fully meshed to
prevent the sending of redundant route advertisements.
When a routing device is configured as a route reflector for a cluster, a route advertised by the route reflector is considered internal if it is received from an internal peer with the same cluster identifier or if both peers have no cluster identifier configured. A route received from an internal peer that belongs to another cluster, that is, with a different cluster identifier, is considered external.
Topology
Figure 1 shows the sample network.
CLI Quick Configuration shows the configuration for all of the devices in Figure 1.
The section #configuration148__policy-advertise-external-st describes the steps on Device R2.
Configuration
CLI Quick Configuration
To quickly
configure this example, copy the following commands, paste them into
a text file, remove any line breaks, change any details necessary
to match your network configuration, and then copy and paste the commands
into the CLI at the [edit] hierarchy level.
Device R1
set interfaces fe-1/2/0 unit 0 description to-R2 set interfaces fe-1/2/0 unit 0 family inet address 10.0.0.1/30 set interfaces lo0 unit 0 family inet address 192.168.0.1/32 set protocols bgp group ext type external set protocols bgp group ext export send-static set protocols bgp group ext peer-as 200 set protocols bgp group ext neighbor 10.0.0.2 set policy-options policy-statement send-static term 1 from protocol static set policy-options policy-statement send-static term 1 from route-filter 172.16.6.0/24 exact set policy-options policy-statement send-static term 1 then accept set policy-options policy-statement send-static term 2 then reject set routing-options static route 172.16.6.0/24 reject set routing-options router-id 192.168.0.1 set routing-options autonomous-system 100
Device R2
set interfaces fe-1/2/0 unit 0 description to-R1 set interfaces fe-1/2/0 unit 0 family inet address 10.0.0.2/30 set interfaces fe-1/2/1 unit 0 description to-R3 set interfaces fe-1/2/1 unit 0 family inet address 10.0.0.5/30 set interfaces lo0 unit 0 family inet address 192.168.0.2/32 set protocols bgp group ext type external set protocols bgp group ext peer-as 100 set protocols bgp group ext neighbor 10.0.0.1 set protocols bgp group int type internal set protocols bgp group int local-address 192.168.0.2 set protocols bgp group int advertise-external set protocols bgp group int neighbor 192.168.0.3 set protocols ospf area 0.0.0.0 interface fe-1/2/1.0 set protocols ospf area 0.0.0.0 interface lo0.0 passive set routing-options router-id 192.168.0.2 set routing-options autonomous-system 200
Device R3
set interfaces fe-1/2/0 unit 6 family inet address 10.0.0.6/30 set interfaces lo0 unit 0 family inet address 192.168.0.3/32 set protocols bgp group int type internal set protocols bgp group int local-address 192.168.0.3 set protocols bgp group int export send-static set protocols bgp group int neighbor 192.168.0.2 set protocols ospf area 0.0.0.0 interface fe-1/2/0.6 set protocols ospf area 0.0.0.0 interface lo0.0 passive set policy-options policy-statement send-static term 1 from protocol static set policy-options policy-statement send-static term 1 then local-preference 200 set policy-options policy-statement send-static term 1 then accept set routing-options static route 172.16.6.0/24 reject set routing-options static route 0.0.0.0/0 next-hop 10.0.0.5 set routing-options autonomous-system 200
Procedure
Step-by-Step Procedure
The following example requires that you navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the Junos OS CLI User Guide.
To configure Device R2:
Configure the device interfaces.
content_copy zoom_out_map[edit interfaces] user@R2# set fe-1/2/0 unit 0 description to-R1 user@R2# set fe-1/2/0 unit 0 family inet address 10.0.0.2/30 user@R2# set fe-1/2/1 unit 0 description to-R3 user@R2# set fe-1/2/1 unit 0 family inet address 10.0.0.5/30 user@R2# set lo0 unit 0 family inet address 192.168.0.2/32
Configure OSPF or another interior gateway protocol (IGP).
content_copy zoom_out_map[edit protocols ospf area 0.0.0.0] user@R2# set interface fe-1/2/1.0 user@R2# set interface lo0.0 passive
Configure the EBGP connection to Device R1.
content_copy zoom_out_map[edit protocols bgp group ext] user@R2# set type external user@R2# set peer-as 100 user@R2# set neighbor 10.0.0.1
Configure the IBGP connection to Device R3.
content_copy zoom_out_map[edit protocols bgp group int] user@R2# set type internal user@R2# set local-address 192.168.0.2 user@R2# set neighbor 192.168.0.3
Add the
advertise-externalstatement to the IBGP group peering session.content_copy zoom_out_map[edit protocols bgp group int] user@R2# set advertise-external
Configure the autonomous system (AS) number and the router ID.
content_copy zoom_out_map[edit routing-options ] user@R2# set router-id 192.168.0.2 user@R2# set autonomous-system 200
Results
From configuration mode, confirm your configuration
by entering the show interfaces, show protocols, show policy-options, and show routing-options commands. If the output does not display the intended configuration,
repeat the instructions in this example to correct the configuration.
user@R2# show interfaces
fe-1/2/0 {
unit 0{
description to-R1;
family inet {
address 10.0.0.2/30;
}
}
}
fe-1/2/1 {
unit 0 {
description to-R3;
family inet {
address 10.0.0.5/30;
}
}
}
lo0 {
unit 0 {
family inet {
address 192.168.0.2/32;
}
}
}
user@R2# show protocols
bgp {
group ext {
type external;
peer-as 100;
neighbor 10.0.0.1;
}
group int {
type internal;
local-address 192.168.0.2;
advertise-external;
neighbor 192.168.0.3;
}
}
ospf {
area 0.0.0.0 {
interface fe-1/2/1.0;
interface lo0.0 {
passive;
}
}
}
user@R2# show routing-options router-id 192.168.0.2; autonomous-system 200;
If you are done configuring the device, enter commit from configuration mode.
Verification
Confirm that the configuration is working properly.
- Verifying the BGP Active Path
- Verifying the External Route Advertisement
- Verifying the Route on Device R3
- Experimenting with the conditional Option
Verifying the BGP Active Path
Purpose
On Device R2, make sure that the 172.16.6.0/24 prefix is in the routing table and has the expected active path.
Action
user@R2> show route 172.16.6
inet.0: 8 destinations, 9 routes (8 active, 1 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.16.6.0/24 *[BGP/170] 00:00:07, localpref 200, from 192.168.0.3
AS path: I, validation-state: unverified
> to 10.0.0.6 via fe-1/2/1.0
[BGP/170] 03:23:03, localpref 100
AS path: 100 I, validation-state: unverified
> to 10.0.0.1 via fe-1/2/0.0
Meaning
Device R2 receives the 172.16.6.0/24 route from both Device R1 and Device R3. The route from Device R3 is the active path, as designated by the asterisk (*). The active path has the highest local preference. Even if the local preferences of the two routes were equal, the route from Device R3 would remain active because it has the shortest AS path.
Verifying the External Route Advertisement
Purpose
On Device R2, make sure that the 172.16.6.0/24 route is advertised toward Device R3.
Action
user@R2> show route advertising-protocol bgp 192.168.0.3 inet.0: 8 destinations, 9 routes (8 active, 1 holddown, 0 hidden) Prefix Nexthop MED Lclpref AS path 172.16.6.0/24 10.0.0.1 100 100 I
Meaning
Device R2 is advertising the 172.16.6.0/24 route toward Device R3.
Verifying the Route on Device R3
Purpose
Make sure that the 172.16.6.0/24 prefix is in Device R3’s routing table.
Action
user@R3> show route 172.16.6.0/24
inet.0: 7 destinations, 8 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.16.6.0/24 *[Static/5] 03:34:14
Reject
[BGP/170] 06:34:43, localpref 100, from 192.168.0.2
AS path: 100 I, validation-state: unverified
> to 10.0.0.5 via fe-1/2/0.6Meaning
Device R3 has the static route and the BGP route for 172.16.6.0/24.
Note that the BGP route is hidden on Device R3 if the route
is not reachable or if the next hop cannot be resolved. To fulfill
this requirement, this example includes a static default route on
Device R3 (static route 0.0.0.0/0 next-hop 10.0.0.5).
Experimenting with the conditional Option
Purpose
See how the conditional option works in
the context of the BGP path selection algorithm.
Action
On Device R2, add the
conditionaloption.content_copy zoom_out_map[edit protocols bgp group int] user@R2# set advertise-external conditional user@R2# commit
On Device R2, check to see if the 172.16.6.0/24 route is advertised toward Device R3.
content_copy zoom_out_mapuser@R2> show route advertising-protocol bgp 192.168.0.3
As expected, the route is no longer advertised. You might need to wait a few seconds to see this result.
On Device R3, deactivate the
then local-preferencepolicy action.content_copy zoom_out_map[edit policy-options policy-statement send-static term 1] user@R3# deactivate logical-systems R3 then local-preference user@R3# commit
On Device R2, ensure that the local preferences of the two paths are equal.
content_copy zoom_out_mapuser@R2> show route 172.16.6.0/24 inet.0: 8 destinations, 9 routes (8 active, 0 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both 172.16.6.0/24 *[BGP/170] 08:02:59, localpref 100 AS path: 100 I, validation-state: unverified > to 10.0.0.1 via fe-1/2/0.0 [BGP/170] 00:07:51, localpref 100, from 192.168.0.3 AS path: I, validation-state: unverified > to 10.0.0.6 via fe-1/2/1.0On Device R2, add the
as-path-ignorestatement.content_copy zoom_out_map[edit protocols bgp] user@R2# set path-selection as-path-ignore user@R2# commit
On Device R2, check to see if the 172.16.6.0/24 route is advertised toward Device R3.
content_copy zoom_out_mapuser@R2> show route advertising-protocol bgp 192.168.0.3 inet.0: 8 destinations, 9 routes (8 active, 0 holddown, 0 hidden) Prefix Nexthop MED Lclpref AS path * 172.16.6.0/24 10.0.0.1 100 100 I
As expected, the route is now advertised because the AS path length is ignored and because the local preferences are equal.
