Cisco Systems OL-14356-01 Configuring the MED Metric for BGP

Implementing BGP on Cisco IOS XR Software

How to Implement BGP on CiscoIOS XR Software

RC-53

Cisco IOS XR Routing Configuration Guide

OL-14356-01

Configuring the MED Metric for BGP

Perform this task to set the multi exit discriminator (MED) to advertise to peers for routes that do not

already have a metric set (routes that were received with no MED attribute).

SUMMARY STEPS

1. configure

2. router bgp as-number

3. default-metric value

4. end

or

commit

DETAILED STEPS

Command or Action Purpose

Step1 configure

Example:

RP/0/RP0/CPU0:router# configure

Enters global configuration mode.

Step2 router bgp as-number

Example:

RP/0/RP0/CPU0:router(config)# router bgp 120

Enters BGP configuration mode, allowing you to configure

the BGP routing process.

Contents

Main Cisco IOS XR Routing Configuration Guide Page CONTENTS Page Page Page Page Page Page Page Page Page Preface Changes to This Document Obtaining Documentation and Submitting a Service Request Page Implementing BGP on Cisco IOS XR Software Prerequisites for Implementing BGP on Cisco IOS XR Software Information About Implementing BGP on Cisco IOS XR Software BGP Functional Overview BGP Router Identifier BGP Default Limits BGP Next Hop Tracking Scoped IPv4/VPNv4 Table Walk Reordered Address Family Processing New Thread for Next-Hop Processing show, clear, and debug Commands Autonomous System Number Formats in BGP BGP Configuration Configuration Modes Router Configuration Mode Router Address Family Configuration Mode Neighbor Configuration Mode Neighbor Address Family Configuration Mode VRF Configuration Mode Neighbor Submode Configuration Templates Template Inheritance Rules RC-12 The following output from the show bgp neighbors command shows that the advertisement interval RC-13 The following output from the show bgp neighbors command shows that the advertisement interval RC-14 The following output from the show bgp neighbors command shows that the advertisement interval 4. Otherwise, the default value is used. In the example that follows, neighbor 10.0.101.5 has the Template Inheritance show bgp neighbors show bgp af-group show bgp session-group show bgp neighbor-group No Default Address Family Routing Policy Enforcement RC-21 Table Policy Update Groups BGP Update Generation and Update Groups BGP Update Group BGP Cost Community How BGP Cost Community Influences the Best Path Selection Process Cost Community Support for Aggregate Routes and Multipaths Influencing Route Preference in a Multiexit IGP Network BGP Cost Community Support for EIGRP MPLS VPN PE-CE with Back-door Links Page Adding Routes to the Routing Information Base BGP Best Path Algorithm Comparing Pairs of Paths Page Order of Comparisons Best Path Change Suppression Administrative Distance Page Multiprotocol BGP Route Dampening Minimizing Flapping BGP Routing Domain Confederation BGP Route Reflectors RC-35 Figure6 Three Fully Meshed iBGP Speakers Router A Router C Router B Figure7 Simple BGP Model with a Route Reflector Page Default Address Family for show Commands Distributed BGP MPLS VPN Carrier Supporting Carrier BGP Keychains IPv6/IPv6 VPN Provider Edge Transport over MPLS IPv6 Provider Edge Multipath VPNv4/VPNv6 over the IP Core Using L2TPv3 Tunnels BGP Multicast VPN IP L3VPN w/L2TPv3 How to Implement BGP on Cisco IOS XR Software Service Provider Page Enabling BGP Routing Page Page Configuring a Routing Domain Confederation for BGP Page Resetting an eBGP Session Immediately Upon Link Failure Logging Neighbor Changes Adjusting BGP Timers Changing the BGP Default Local Preference Value Page Configuring the MED Metric for BGP Configuring BGP Weights Page Tuning the BGP Best-Path Calculation Page Indicating BGP Back-door Routes Page Configuring Aggregate Addresses Redistributing iBGP Routes into IGP Page Redistributing Prefixes into Multiprotocol BGP Page Page Configuring BGP Route Dampening Page Page RC-69 Step8 Clears BGP flap statistics for all routes. Displays BGP flap statistics for the specified route policy. Step9 RC-70 Step12 Clears BGP flap statistics for all paths that match the specified regular expression. Step13 Clears BGP flap statistics for the specified route policy. Applying Policy When Updating the Routing Table Page Setting BGP Administrative Distance Configuring a BGP Neighbor Group and Neighbors Page Page Configuring a Route Reflector for BGP Page Configuring BGP Route Filtering by Route Policy Page Configuring BGP Next-hop Trigger Delay Page Disabling Next-hop Processing on BGP Updates Configuring BGP Community and Extended-Community Advertisements Page Configuring the BGP Cost Community Page Page Page RC-90 Configuring Software to Store Updates from a Neighbor Page Configuring Distributed BGP Page Page Configuring a VPN Routing and Forwarding Instance in BGP Defining the Virtual Routing and Forwarding Tables in Provider Edge Routers Page Configuring the Route Distinguisher Page Configuring PE-PE or PE-RR Interior BGP sessions Page Page Configuring Route Reflector to Hold Routes That Have a Defined Set of RT Communities Page Configuring BGP as a PE-CE Protocol Page Page Page BGP Load Balancing Page Redistribution of IGPs to BGP Page Page Configuring Keychains for BGP Configuring an MDT Address Family Session in BGP Page Page Disabling a BGP Neighbor Page Resetting Neighbors Using BGP Inbound Soft Reset Resetting Neighbors Using BGP Outbound Soft Reset Resetting Neighbors Using BGP Hard Reset Clearing Caches, Tables, and Databases Displaying System and Network Statistics Page Displaying BGP Process Information Monitoring BGP Update Groups Configuration Examples for Implementing BGP on Cisco IOS XR Enabling BGP: Example RC-128 RC-129 Displaying BGP Update Groups: Example The following is sample output from the show bgp update-group command run in EXEC mode: BGP Neighbor Configuration: Example BGP Confederation: Example RC-131 BGP Route Reflector: Example RC-132 BGP MDT Address Family Configuration: Example The following example shows how to configure an MDT address family in BGP: For detailed information about BGP commands, see Cisco IOS XR Routing Command Reference document. Page Page Implementing EIGRP on Cisco IOS XR Software Prerequisites for Implementing EIGRP on Cisco IOS XR Software Restrictions for Implementing EIGRP on Cisco IOS XR Software Information About Implementing EIGRP on Cisco IOS XR EIGRP Functional Overview EIGRP Features EIGRP Components EIGRP Configuration Grouping EIGRP Configuration Modes EIGRP Interfaces Redistribution for an EIGRP Process Metric Weights for EIGRP Routing Mismatched K Values The Goodbye Message Percentage of Link Bandwidth Used for EIGRP Packets Floating Summary Routes for an EIGRP Process . . . . . . . . Split Horizon for an EIGRP Process . . . . Adjustment of Hello Interval and Hold Time for an EIGRP Process Stub Routing for an EIGRP Process Route Policy Options for an EIGRP Process EIGRP Layer 3 VPN PE-CE Site-of-Origin Router Interoperation with the Site-of-Origin Extended Community IPv6 and IPv6 VPN Provider Edge Support over MPLS and IP How to Implement EIGRP on Cisco IOS XR Software Enabling EIGRP Routing Page Configuring Route Summarization for an EIGRP Process Page Redistributing Routes for EIGRP Page Creating a Route Policy and Attaching It to an EIGRP Process Page Page Configuring Stub Routing for an EIGRP Process Configuring EIGRP as a PE-CE Protocol Page Redistributing BGP Routes into EIGRP Page Monitoring EIGRP Routing Page Page Configuration Examples for Implementing EIGRP on Cisco IOS XR Software Configuring a Basic EIGRP Configuration: Example RC-167 Configuring an EIGRP Stub Operation: Example Configuring an EIGRP PE-CE Configuration with Prefix-Limits: Example Page Page Page Implementing OSPF on Cisco IOS XR Software Prerequisites for Implementing OSPF on Cisco IOS XR Software Information About Implementing OSPF on Cisco IOS XR OSPF Functional Overview Page Key Features Supported in the Cisco IOS XR OSPF Implementation Comparison of Cisco IOS XR OSPFv3 and OSPFv2 OSPF Hierarchical CLI and CLI Inheritance OSPF Routing Components Autonomous Systems Areas Backbone Area Stub Area Not-so-Stubby Area Routers Area Border Routers Autonomous System Boundary Routers (ASBR) Interior Routers OSPF Process and Router ID Supported OSPF Network Types Route Authentication Methods for OSPF Plain Text Authentication MD5 Authentication Authentication Strategies Key Rollover Neighbors and Adjacency for OSPF Designated Router (DR) for OSPF Default Route for OSPF Link-State Advertisement Types for OSPF Version 2 Link-State Advertisement Types for OSPFv3 Virtual Link and Transit Area for OSPF OSPFv2 Shamlink Support for MPLS VPN Page Route Redistribution for OSPF OSPF Shortest Path First Throttling Nonstop Forwarding for OSPF Version 2 Graceful Restart for OSPFv3 Modes of Graceful Restart Operation Restart Mode Helper Mode Graceful Restart Requirements and Restrictions Warm Standby and Nonstop Routing for OSPF Version 2 Multicast-Intact Support for OSPF Load Balancing in OSPF Version 2 and OSPFv3 Multi-Area Adjacency for OSPF Version 2 Label Distribution Protocol IGP Auto-configuration for OSPF OSPF Authentication Message Digest Management GTSM TTL Security Mechanism for OSPF Path Computation Element for OSPFv2 How to Implement OSPF on Cisco IOS XR Software Enabling OSPF Page Page Configuring Stub and Not-So-Stubby Area Types Page Configuring Neighbors for Nonbroadcast Networks Page Page Page Page Configuring Authentication at Different Hierarchical Levels for OSPF Version 2 Page Page Controlling the Frequency That the Same LSA Is Originated or Accepted for OSPF Page Creating a Virtual Link with MD5 Authentication to Area 0 for OSPF Page Page Page Summarizing Subnetwork LSAs on an OSPF ABR Page Redistributing Routes from One IGP into OSPF Page Page Page Configuring OSPF Shortest Path First Throttling Page Page Page Page Configuring Nonstop Forwarding Specific to Cisco for OSPF Version 2 Page Configuring OSPF Version 2 for MPLS Traffic Engineering Page Page RC-229 This section provides the following output examples: Sample Output for the show ospf Command Before Configuring MPLS TE Sample Output for the show ospf mpls traffic-eng Command Configuring OSPFv3 Graceful Restart DETAILED STEP Displaying Information About Graceful Restart Configuring an OSPFv2 Sham Link Page Page Enabling Nonstop Routing for OSPFv2 Enabling Multicast-intact for OSPFv2 Associating Interfaces to a VRF Page Configuring OSPF as a Provider Edge to Customer Edge (PE-CE) Protocol Page Page Creating Multiple OSPF Instances (OSPF Process and a VRF) Configuring Multi-area Adjacency Page Configuring Label Distribution Protocol IGP Auto-configuration for OSPF Configuring Authentication Message Digest Management for OSPF Page Page RC-250 The following example shows output for configured keys that are active: Configuring Generalized TTL Security Mechanism (GTSM) for OSPF Page Page Verifying OSPF Configuration and Operation Configuration Examples for Implementing OSPF on Cisco IOS XR Cisco IOS XR for OSPF Version 2 Configuration: Example RC-256 CLI Inheritance and Precedence for OSPF Version 2: Example RC-258 MPLS TE for OSPF Version 2: Example ABR with Summarization for OSPFv3: Example The following example shows the prefix range 2300::/16 summarized from area 1 into the backbone: ABR Stub Area for OSPFv3: Example The following example shows that area 1 is configured as a stub area: Route Redistribution for OSPFv3: Example Virtual Link Configured Through Area 1 for OSPFv3: Example ABR 1 Configuration ABR 2 Configuration RC-260 Virtual Link Configured with MD5 Authentication for OSPF Version 2: Example In this example, only area 1 interfaces on router ABR3 use MD5 authentication: VPN Backbone and Sham Link Configured for OSPF Version 2: Example RC-261 Page Page Page Implementing IS-IS on Cisco IOS XR Software Prerequisites for Implementing IS-IS on Cisco IOS XR Software Restrictions for Implementing IS-IS on Cisco IOS XR Software Information About Implementing IS-IS on Cisco IOS XR Software IS-IS Functional Overview Key Features Supported in the Cisco IOS XR IS-IS Implementation IS-IS Configuration Grouping IS-IS Configuration Modes Router Configuration Mode Router Address Family Configuration Mode Interface Configuration Mode IS-IS Interfaces Multitopology Configuration IPv6 Routing and Configuring IPv6 Addressing Limit LSP Flooding Flood Blocking on Specific Interfaces Maximum LSP Lifetime and Refresh Interval Overload Bit Configuration During Multitopology Operation Single-Topology IPv6 Support Multitopology IPv6 Support IS-IS Authentication Nonstop Forwarding Multi-Instance IS-IS Multiprotocol Label Switching Traffic Engineering Overload Bit on Router Default Routes Attached Bit on an IS-IS Instance IS-IS Support for Route Tags Multicast-Intact Feature Multicast Topology Support Using IS-IS MPLS Label Distribution Protocol IGP Synchronization MPLS LDP-IGP Synchronization Compatibility with LDP Graceful Restart MPLS LDP-IGP Synchronization Compatibility with IGP Nonstop Forwarding Label Distribution Protocol IGP Auto-configuration MPLS TE Forwarding Adjacency MPLS TE Interarea Tunnels IP Fast Reroute How to Implement IS-IS on Cisco IOS XR Software Enabling IS-IS and Configuring Level 1 or Level 2 Routing Page Page Configuring Single Topology for IS-IS Page Page Page Configuring Multitopology for IS-IS Controlling LSP Flooding for IS-IS Page Page Page Configuring Nonstop Forwarding for IS-IS Page Configuring Authentication for IS-IS Page Configuring Keychains for IS-IS Page Configuring MPLS Traffic Engineering for IS-IS Prerequisite Page Page Tuning Adjacencies for IS-IS Page Page Setting SPF Interval for a Single-Topology IPv4 and IPv6 Configuration Page Customizing Routes for IS-IS Page Page Configuring MPLS LDP IS-IS Synchronization Page Enabling Multicast-Intact Tagging IS-IS Interface Routes Page Setting the Priority for Adding Prefixes to the RIB Page Configuring IP Fast Reroute Loop-free Alternate Configuration Examples for Implementing IS-IS on Cisco IOS XR Configuring Single-Topology IS-IS for IPv6: Example Configuring Multitopology IS-IS for IPv6: Example Redistributing IS-IS Routes Between Multiple Instances: Example RC-316 Tagging Routes: Example The following example show how to tag routes. Page Page Implementing and Monitoring RIB on Cisco IOS XR Software Prerequisites for Implementing RIB on Cisco IOS XR Software Information About RIB Configuration Overview of RIB RIB Data Structures in BGP and Other Protocols RIB Administrative Distance RIB Support for IPv4 and IPv6 RIB Statistics IPv6 and IPv6 VPN Provider Edge Transport over MPLS IP Fast Reroute RIB Quarantining How to Deploy and Monitor RIB Verifying RIB Configuration Using the Routing Table Verifying Networking and Routing Problems Page Disabling RIB Next-hop Dampening Configuration Examples for RIB Monitoring RC-328 Output of show route Command: Example The following is sample output from the show route command when entered without an address: Output of show route backup Command: Example The following is sample output from the show route backup command: Output of show route best-local Command: Example Output of show route connected Command: Example The following is sample output from the show route connected command: Output of show route local Command: Example The following is sample output from the show route local command: Output of show route longer-prefixes Command: Example Page Page Page Implementing RIP on Cisco IOS XR Software Information About Implementing RIP on Cisco IOS XR Software Prerequisites for Implementing RIP on Cisco IOS XR Software RIP Functional Overview Split Horizon for RIP Route Timers for RIP Route Redistribution for RIP Default Administrative Distances for RIP Routing Policy Options for RIP How to Implement RIP on Cisco IOS XR Software Enabling RIP Customize RIP Page Page Control Routing Information Page Creating a Route Policy for RIP Page Page Configuration Examples for Implementing RIP on Cisco IOS XR Configuring a Basic RIP Configuration: Example Configuring RIP on the Provider Edge: Example Adjusting RIP Timers for each VRF Instance: Example Configuring Redistribution for RIP: Example Configuring Route Policies for RIP: Example RC-350 Configuring Passive Interfaces and Explicit Neighbors for RIP: Example The following sections provide references related to implementing RIP on CiscoIOS XR software. Controlling RIP Routes: Example Page Page Implementing Routing Policy on Cisco IOS XR Software Prerequisites for Implementing Routing Policy on Cisco IOS XR Information About Implementing Routing Policy on Cisco IOS XR Routing Policy Language Routing Policy Language Overview Routing Policy Language Structure Names Sets as-path-set community-set extcommunity-set prefix-set rd-set Routing Policy Language Components Routing Policy Language Usage Page Routing Policy Configuration Basics Policy Definitions Parameterization Parameterization at Attach Points Global Parameterization Semantics of Policy Application Boolean Operator Precedence Multiple Modifications of the Same Attribute When Attributes Are Modified Default Drop Disposition Control Flow Policy Verification Range Checking Incomplete Policy and Set References Attached Policy Modification Verification of Attribute Comparisons and Actions Policy Statements Remark Disposition Page Action If Boolean Conditions apply Attach Points BGP Policy Attach Points Aggregation Dampening Default Originate Neighbor Export Neighbor Import Network Show BGP Table Policy Import Export Retain Route-Target Allocate-Label Neighbor-ORF Next-hop Clear-Policy Debug BGP Attributes and Operators Page Page Page Page Page Page Page Page Page OSPF Policy Attach Points Area-in Area-out OSPF Attributes and Operators OSPFv3 Policy Attach Points OSPFv3 Attributes and Operators IS-IS Policy Attach Points Inter-area-propagate IS-IS Attributes and Operators EIGRP Policy Attach Points Default-Accept-In Default-Accept-Out Policy-In Policy-Out If-Policy-In If-Policy-Out EIGRP Attributes and Operators RIP Policy Attach Points Global-Inbound Global-Outbound Interface-Inbound Interface-Outbound RIP Attributes and Operators Attached Policy Modification Nonattached Policy Modification Editing Routing Policy Configuration Elements Editing Routing Policy Configuration Elements Using the Nano Editor Editing Routing Policy Configuration Elements Using the Emacs Editor Editing Routing Policy Configuration Elements Using the Vim Editor Editing Routing Policy Configuration Elements Using the CLI How to Implement Routing Policy on Cisco IOS XR Software Defining a Route Policy Attaching a Routing Policy to a BGP Neighbor Page Modifying a Routing Policy Using a Text Editor Configuration Examples for Implementing Routing Policy on Cisco IOS XR Software Routing Policy Definition: Example Simple Inbound Policy: Example Modular Inbound Policy: Example Translating Cisco IOS Route Maps to Cisco IOS XR Routing Policy Language: Example Page Page Implementing Static Routes on Cisco IOS XR Software Prerequisites for Implementing Static Routes on Cisco IOS XR Information About Implementing Static Routes on Cisco IOS XR Static Route Functional Overview Default Administrative Distance Directly Connected Routes Recursive Static Routes Fully Specified Static Routes Floating Static Routes Default VRF IPv4 and IPv6 Static VRF Routes IPv6/IPv6 VPN Provider Edge Transport over MPLS How to Implement Static Routes on Cisco IOS XR Software Configuring a Static Route Configuring a Floating Static Route Page Configuring Static Routes Between PE-CE Routers Page Changing the Maximum Number of Allowable Static Routes Associating a VRF with a Static Route Page Configuration Examples Configuring Traffic Discard: Example Configuring a Fixed Default Route: Example Configuring a Floating Static Route: Example Configuring a Static Route Between PE-CE Routers: Example Page Page INDEX A B Page C D E F G H I K L M N O Page P R Page Page Page S T U V W