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MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

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MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

Table Of Contents

MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

Contents

Prerequisites for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Restrictions for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Information About MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Feature Design of MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Benefits of MPLS—VPN Explicit Null Label Support BGP IPv4 Label Session

How to Configure MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Configuring CSC with BGP

Verifying Explicit Null Configuration

Configuration Examples for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Configuring CSC-CE with BGP: Example

Verifying Explicit Null Configuration: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

debug ip bgp

neighbor send-label explicit-null

show ip bgp neighbors

show ip bgp vpnv4

show mpls forwarding-table

Feature Information for MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

Glossary


MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session


First Published: January 20, 2004
Last Updated: June 29, 2007

The MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session feature provides a method to advertise explicit null in a Border Gateway Protocol (BGP) label session for a carrier supporting carrier (CSC) customer edge (CE) router.

Finding Feature Information in This Module

Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session" section.

Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

Prerequisites for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Restrictions for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Information About MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

How to Configure MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Configuration Examples for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Additional References

Command Reference

Feature Information for MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

Glossary

Prerequisites for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

You must configure your network for MPLS VPN.

You must configure BGP to distribute labels between the CSC-CE and CSC-provider edge (PE) routers.

Restrictions for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Configure an explicit null label only in a CSC-CE topology.

Configure an explicit null label only on a per-neighbor basis.

Information About MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

To configure MPLS—VPN Explicit Null Label Support BGP IPv4 Label Session, you need to understand the following concepts:

Feature Design of MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

Benefits of MPLS—VPN Explicit Null Label Support BGP IPv4 Label Session

Feature Design of MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

On a CSC-CE with BGP IPv4 label distribution, BGP advertises an implicit null label for directly connected routes. This causes the previous hop (penultimate) router to do penultimate hop popping (PHP).

The MPLS—VPN Explicit Null Label Support BGP IPv4 Label Session feature makes the penultimate router swap the incoming label for (or impose) the explicit null label. This action forces the egress router to process the explicit null label by popping it and inspecting the packet that remains.

Benefits of MPLS—VPN Explicit Null Label Support BGP IPv4 Label Session

Improved Quality of Service

The explicit null label helps to preserve quality of service (QoS) bits from one service level agreement (SLA) to another until the packets reach their CSC-CE destination.

How to Configure MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

This section contains the following procedures:

Configuring CSC with BGP (required)

Verifying Explicit Null Configuration (optional)

Configuring CSC with BGP

Perform this task to configure CSC with BGP.

SUMMARY STEPS

1. enable

2. configure terminal

3. router bgp autonomous system-number

4. address-family ipv4 [unicast]

5. neighbor ip-address send-label explicit-null

6. neighbor {ip-address | peer-group-name | ipv6-address} activate

7. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

router bgp autonomous system-number

Example:

Router(config)# router bgp 100

Enters router configuration mode and configures the router to run a BGP process.

Step 4 

address-family ipv4 [unicast]

Example:

Router(config-router)# address-family ipv4

Enters address family configuration mode for the IPv4 address family from which you can configure routing sessions that use standard IPv4 address prefixes.

Step 5 

neighbor ip-address send-label explicit-null

Example:

Router(config-router-af)# neighbor 10.0.0.2 send-label explicit-null

Send-label advertises the capability of a router to send MPLS labels with BGP routes.

The explicit-null keyword allows a CSC-CE router to send labels with a value of 0 to its neighbor.

Step 6 

neighbor {ip-address | peer-group-name | ipv6-address} activate

Example:

Router(config-router-af)# neighbor 192.168.99.70 activate

Enables the neighbor to exchange prefixes for the IPv4 address family with the local router.

Step 7 

exit

Example:

Router(config-router-af)# exit

Exits address family configuration mode and returns the router to router configuration mode.

Repeat this step to exit router configuration mode and return the router to global configuration mode.

Verifying Explicit Null Configuration

Perform this task to verify that the explicit null option is configured.

SUMMARY STEPS

1. enable

2. show ip bgp neighbors [ip-address [advertised-routes | dampened-routes | flap-statistics |
paths [regexp] | received prefix-filter | received-routes | routes]]

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

show ip bgp neighbors [ip-address [advertised-routes | dampened-routes | flap-statistics | paths [regexp] | received prefix-filter | received-routes | routes]]


Example:

Router# show ip bgp neighbors

Displays information about the TCP and BGP connections to neighbors including explicit null.

The optional ip-address argument displays the IP address of the neighbor whose routes you have learned If you omit this argument, all neighbors are displayed.

The optional advertised-routes keyword displays all the routes the router has advertised to the neighbor.

The optional dampened-routes keyword displays the dampened routes to the neighbor at the IP address specified.

The optional flap statistics keyword displays the flap statistics of the routes learned from the specified neighbor (eBGP peers only)

The optional path regexp keyword argument combination displays autonomous system paths learned from the specified neighbor. An optional regular expression can be used to filter the output.

The optional received prefix-filter keyword displays the configured prefix list filter for the specified IP address.

The optional received-routes keyword displays all received routes (both accepted and rejected) from the specified neighbor.

The optional routes keyword displays all routes that are received and accepted. This is a subset of the output from the received-routes keyword.

Configuration Examples for MPLS—VPN Explicit Null Label Support with BGP IPv4 Label Session

This section provides the following configuration examples:

Configuring CSC-CE with BGP: Example

Verifying Explicit Null Configuration: Example

Configuring CSC-CE with BGP: Example

In the following CSC-CE example, CSC is configured with BGP to distribute labels and to advertise explicit null for all its connected routes:

Router(config-router-af)# neighbor 10.0.0.0 send-label explicit-null

router bgp 100
 bgp log-neighbor-changes
 neighbor 10.0.0.0 remote-as 200
 !
address-family ipv4
 neighbor 10.0.0.0 activate
 neighbor 10.0.0.0 send-label explicit-null
 no auto-summary
 no synchronization
 exit-address-family 

Verifying Explicit Null Configuration: Example

This section provides sample output for the show ip bgp neighbors command.

Sample Output for the show ip bgp neighbors Command

Sample Output for the show ip bgp neighbors Command

In this example, the show ip bgp neighbors command displays information about connected BGP neighbors, including IP addresses, version numbers, neighbor capabilities, message statistics, and address family statistics that show if explicit null is configured.

Router# show ip bgp neighbors 

BGP neighbor is 10.0.0.2,  remote AS 300, external link
  BGP version 4, remote router ID 10.0.0.20
  BGP state = Established, up for 00:45:16
  Last read 00:00:16, hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
    Route refresh: advertised and received(new)
    Address family IPv4 Unicast: advertised and received
    ipv4 MPLS Label capability: advertised and received
  Message statistics:
    InQ depth is 0
    OutQ depth is 0
                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                1          2
    Keepalives:            47         47
    Route Refresh:          0          0
    Total:                 49         50
  Default minimum time between advertisement runs is 30 seconds

 For address family: IPv4 Unicast
  BGP table version 9, neighbor version 9/0
  Output queue sizes : 0 self, 0 replicated
  Index 1, Offset 0, Mask 0x2
  Member of update-group 1
  My AS number is allowed for 3 number of times
  AF-dependant capabilities:
    Outbound Route Filter (ORF) type (128) Prefix-list:
  Sending Prefix & Label(advertise explicit-null set)       !Explicit null is configured
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               3          3 (Consumes 144 bytes)
    Prefixes Total:                 3          6
    Implicit Withdraw:              0          3
    Explicit Withdraw:              0          0
    .........	
    .........

Additional References

The following sections provide references related to the MPLS—VPN Explicit Null Label with BGP IPv4 Label Session feature.

Related Documents


Standards

Standards
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.


MIBs

MIBs
MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs


RFCs

RFCs
Title

RFC 1163

A Border Gateway Protocol

RFC 1164

Application of the Border Gateway Protocol in the Internet

RFC 2283

Multiprotocol Extensions for BGP-4

RFC 2547

BGP/MPLS VPNs

RFC 3107

Carrying Label Information in BGP-4


Technical Assistance

Description
Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport


Command Reference

This section documents only commands that are new or modified.

debug ip bgp

neighbor send-label explicit-null

show ip bgp neighbors

show ip bgp vpnv4

show mpls forwarding-table

debug ip bgp

To display information related to processing of the Border Gateway Protocol (BGP), use the debug ip bgp command in privileged EXEC mode. To disable debugging output, use the no form of this command.

debug ip bgp [A.B.C.D. | dampening | events | in | keepalives | out | updates | vpnv4 | mpls]

no debug ip bgp [A.B.C.D. | dampening | events | in | keepalives | out | updates | vpnv4 | mpls]

Cisco 10000 Series Router

debug ip bgp [A.B.C.D. | dampening | events | in | keepalives | out | updates | vpnv4 | mpls | all | groups | import | ipv4 | ipv6]

no debug ip bgp [A.B.C.D. | dampening | events | in | keepalives | out | updates | vpnv4 | mpls | all | groups | import | ipv4 | ipv6]

Syntax Description

A.B.C.D.

(Optional) Displays the BGP neighbor IP address.

dampening

(Optional) Displays BGP dampening.

events

(Optional) Displays BGP events.

in

(Optional) Displays BGP inbound information.

keepalives

(Optional) Displays BGP keepalives.

out

(Optional) Displays BGP outbound information.

updates

(Optional) Displays BGP updates.

vpnv4

(Optional) Displays Virtual Private Network version 4 (VPNv4) Network Layer Reachability Information (NLRI).

mpls

(Optional) Displays the Multiprotocol Label Switching (MPLS) information.

all

(Optional) Displays all address family information.

groups

(Optional) Displays BGP configuration and update groups information.

import

(Optional) Displays BGP import routes to a VPN routing and forwarding (VRF) instance across address family information.

ipv4

(Optional) Displays BGP IPv4 address family information.

ipv6

(Optional) Displays BGP IPv6 address family information.


Command Modes

Privileged EXEC (#)

Command History

Release
Modification

12.0(5)T

This command was introduced.

12.0(21)ST

This command was integrated into Cisco IOS Release 12.0(21)ST. The mpls keyword was added.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.

12.0(23)S

This command was integrated into Cisco IOS Release 12.0(23)S.

12.2(11)S

This feature was integrated into Cisco IOS Release 12.2(11)S.

12.2(13)T

The mpls keyword was added.

12.0(24)S

This command was integrated into Cisco IOS Release 12.0(24)S.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.2(17b)SXA

This command was integrated into Cisco IOS Release 12.2(17b)SXA.

12.0(27)S

The command output was modified to show explicit-null label information.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(31)SB

This command was integrated into Cisco IOS Release 12.2(31)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.


Usage Guidelines

Use this command with the updates and mpls keywords to display explicit-null label information.

Examples

The following is sample output from the debug ip bgp command:

Router# debug ip bgp vpnv4 

03:47:14:vpn:bgp_vpnv4_bnetinit:100:2:10.0.0.0/8
03:47:14:vpn:bnettable add:100:2:10.0.0.0/8
03:47:14:vpn:bestpath_hook route_tag_change for vpn2:10.0.0.0/255.0.0.0(ok)
03:47:14:vpn:bgp_vpnv4_bnetinit:100:2:10.0.0.0/8
03:47:14:vpn:bnettable add:100:2:10.0.0.0/8
03:47:14:vpn:bestpath_hook route_tag_change for vpn2:10.0.0.0/255.0.0.0(ok)
03:47:14:vpn:bgp_vpnv4_bnetinit:100:2:10.0.0.0/8
03:47:14:vpn:bnettable add:100:2:10.0.0.0/8
03:47:14:vpn:bestpath_hook route_tag_chacle ip bgp *nge for vpn2:10.0.0.0/255.0.0.0(ok)

The following example shows sample output, including the explicit-null label, from the debug ip bgp updates and the debug ip bgp mpls commands:

Router# debug ip bgp updates 

BGP updates debugging is on

Router# debug ip bgp mpls

BGP MPLS labels debugging is on
Router#
01:33:53: BGP(0): route 10.10.10.10/32 up
01:33:53: BGP(0): nettable_walker 10.10.10.10/32 route sourced locally
01:33:53: BGP: adding MPLS label to 10.10.10.10/32
01:33:53: BGP: check on 10.10.10.10/8 in LDP - ok
01:33:53: BGP: label imp-null allocated via LDP
01:33:53: BGP-IPv4: send exp-null label for 10.10.10.10/32
01:33:53: BGP-IPv4: Send prefix 10.10.10.10/32, label exp-null    !explicit-null label 
being sent
01:33:53: BGP(0): 10.10.10.11 send UPDATE (format) 10.10.10.10/32, next 10.10.10.12, 
metric 0, path , mpls label 0 !label value is 0
01:33:53: BGP(0): updgrp 1 - 10.10.10.12 enqueued 1 updates, average/maximum size (bytes) 
61/61

neighbor send-label explicit-null

To enable a Border Gateway Protocol (BGP) router to send Multiprotocol Label Switching (MPLS) labels with explicit-null information for a CSC-CE router and BGP routes to a neighboring CSC-PE router, use the neighbor send-label explicit-null command in address family configuration mode or router configuration mode. To disable a BGP router from sending MPLS labels with explicit-null information, use the no form of this command.

neighbor ip-address send-label explicit-null

no neighbor ip-address send-label explicit-null

Syntax Description

ip-address

IP address of the neighboring router.


Command Default

None

Command Modes

Address family configuration (config-router-af)
Router configuration (config-router)

Command History

Release
Modification

12.0(27)S

This command was introduced.

12.4

This command was integrated into Cisco IOS Release 12.4

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.


Usage Guidelines

This command enables a CSC-CE router to use BGP to distribute MPLS labels with a value of zero for explicit-null instead of implicit-null along with IPv4 routes to a CSC-PE peer router.

You must issue this command only on the local CSC-CE router.

You can use this command only with IPv4 addresses.

Examples

In the following CSC-CE example, CSC is configured with BGP to distribute labels and to advertise explicit null for all its connected routes:

Router# configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)# router bgp 100

Router(config-router)# neighbor 10.0.0.2 remote-as 300

Router(config-router)# address-family ipv4

Router(config-router-af)# neighbor 10.0.0.2 send-label explicit-null

In the following CSC-PE example, CSC is configured with BGP to distribute labels:

Router# configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)# router bgp 300

Router(config-router)# neighbor 10.0.0.1 remote-as 100

Router(config-router)# address-family ipv4 vrf v1

Router(config-router-af)# neighbor 10.0.0.1 send-label

Note Explicit null is not applicable on a CSC-PE router.


Related Commands

Command
Description

neighbor activate

Enables the exchange of information with a neighboring router.

neighbor send-label

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.


show ip bgp neighbors

To display information about Border Gateway Protocol (BGP) and TCP connections to neighbors, use the show ip bgp neighbors command in user or privileged EXEC mode.

show ip bgp neighbors [ip-address [advertised-routes | dampened-routes | flap-statistics |
paths [reg-exp] | received prefix-filter | received-routes | routes | policy [detail]]]

Syntax Description

ip-address

(Optional) IP address of a neighbor. If this argument is omitted, all neighbors are displayed.

advertised-routes

(Optional) Displays all routes that have been advertised to neighbors.

dampened-routes

(Optional) Displays the dampened routes received from the specified neighbor.

flap-statistics

(Optional) Displays the flap statistics of the routes learned from the specified neighbor (external BGP peers only).

paths reg-exp

(Optional) Displays autonomous system paths learned from the specified neighbor. An optional regular expression can be used to filter the output.

received prefix-filter

(Optional) Displays the prefix-list (outbound route filter [ORF]) sent from the specified neighbor.

received-routes

(Optional) Displays all received routes (both accepted and rejected) from the specified neighbor.

routes

(Optional) Displays all routes that are received and accepted. The output displayed when this keyword is entered is a subset of the output displayed by the received-routes keyword.

policy

(Optional) Displays the policies applied to this neighbor per address family.

detail

(Optional) Displays detailed policy information such as route maps, prefix lists, community lists, access control lists (ACLs) and AS-path filter lists.


Command Default

The output of this command displays information for all neighbors.

Command Modes

User EXEC (>)
Privileged EXEC (#)

Command History

Release
Modification

10.0

This command was introduced.

11.2

The received-routes keyword was added.

12.0(18)S

The output was modified to display the no-prepend configuration option and this command was integrated into Cisco IOS Release 12.0(18)S.

12.2(4)T

The received and prefix-filter keywords were added, and this command was integrated into Cisco IOS Release 12.2(4)T.

12.0(21)ST

The output was modified to display Multiprotocol Label Switching (MPLS) label information.

12.0(22)S

Support for the BGP graceful restart capability was integrated into the output. Support for the Cisco 12000 series routers (Engine 0 and Engine 2) was also added.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.2(15)T

Support for the BGP graceful restart capability was integrated into the output.

12.0(25)S

The policy and detail keywords were added.

12.2(17b)SXA

This command was integrated into Cisco IOS Release 12.2(17b)SXA.

12.0(27)S

The command output was modified to support the BGP TTL Security Check feature and to display explicit-null label information.

12.3(7)T

The command output was modified to support the BGP TTL Security Check feature and to display explicit-null label information.

12.0(31)S

Support for the Bidirectional Forwarding Detection (BFD) feature was integrated into the output.

12.2(18)SXE

Support for the Bidirectional Forwarding Detection (BFD) feature was integrated into the output.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.4(4)T

Support for the Bidirectional Forwarding Detection (BFD) feature was integrated into the output.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA, and the output was modified to support BGP TCP path MTU discovery.

12.4(11)T

Support for the policy and detail keywords was integrated into Cisco IOS Release 12.4(11)T.

12.2(33)SRB

Support for the policy and detail keywords was integrated into Cisco IOS Release 12.2(33)SRB.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.


Usage Guidelines

Use the show ip bgp neighbors command to display BGP and TCP connection information for neighbor sessions. For BGP, this includes detailed neighbor attribute, capability, path, and prefix information. For TCP, this includes statistics related to BGP neighbor session establishment and maintenance.

Prefix activity is displayed based on the number of prefixes that are advertised and withdrawn. Policy denials display the number of routes that were advertised but then ignored based the function or attribute that is displayed in the output.

Cisco IOS Release 12.0(25)S, 12.4(11)T, 12.2(33)SRB, and Later Releases

When BGP neighbors use multiple levels of peer templates it can be difficult to determine which policies are applied to the neighbor.

In Cisco IOS Release 12.0(25)S, 12.4(11)T, 12.2(33)SRB and later releases, the policy and detail keywords were added to display the inherited policies and the policies configured directly on the specified neighbor. Inherited policies are policies that the neighbor inherits from a peer-group or a peer-policy template.

Examples

Example output is different for the various keywords available for the show ip bgp neighbors command. To view the appropriate output, choose one of the following sections:

show ip bgp neighbors: Example

show ip bgp neighbors advertised-routes: Example

show ip bgp neighbors paths: Example

show ip bgp neighbors received prefix-filter: Example

show ip bgp neighbors policy: Example

Cisco IOS Release 12.0(31)S and 12.4(4)T: Example

Cisco IOS Release 12.2(33)SRA: Example

show ip bgp neighbors: Example

The following example shows output for the BGP neighbor at 10.108.50.2. This neighbor is an internal BGP (iBGP) peer. This neighbor supports the route refresh and graceful restart capabilities.

Router# show ip bgp neighbors 10.108.50.2 

BGP neighbor is 10.108.50.2,  remote AS 1, internal link
  BGP version 4, remote router ID 192.168.252.252 
  BGP state = Established, up for 00:24:25
  Last read 00:00:24, last write 00:00:24, hold time is 180, keepalive interval is 
   60 seconds 
  Neighbor capabilities:
    Route refresh: advertised and received(old & new)
    MPLS Label capability: advertised and received 
    Graceful Restart Capability:advertised and received 
    Address family IPv4 Unicast: advertised and received
  Message statistics:
    InQ depth is 0
    OutQ depth is 0
                         Sent       Rcvd
    Opens:                  3          3
    Notifications:          0          0
    Updates:                0          0
    Keepalives:           113        112
    Route Refresh:          0          0
    Total:                116        115
  Default minimum time between advertisement runs is 5 seconds

 For address family: IPv4 Unicast
  BGP table version 1, neighbor version 1/0
 Output queue size : 0
  Index 1, Offset 0, Mask 0x2
  1 update-group member
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               0          0
    Prefixes Total:                 0          0
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          0
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Total:                                0          0
  Number of NLRIs in the update sent: max 0, min 0

  Connections established 3; dropped 2
  Last reset 00:24:26, due to Peer closed the session 
External BGP neighbor may be up to 2 hops away.
Connection state is ESTAB, I/O status: 1, unread input bytes: 0        
Connection is ECN Disabled 
Local host: 10.108.50.1, Local port: 179 
Foreign host: 10.108.50.2, Foreign port: 42698 

Enqueued packets for retransmit: 0, input: 0  mis-ordered: 0 (0 bytes) 

Event Timers (current time is 0x68B944): 
Timer          Starts    Wakeups            Next
Retrans            27          0             0x0
TimeWait            0          0             0x0
AckHold            27         18             0x0
SendWnd             0          0             0x0
KeepAlive           0          0             0x0
GiveUp              0          0             0x0
PmtuAger            0          0             0x0
DeadWait            0          0             0x0

iss: 3915509457  snduna: 3915510016  sndnxt: 3915510016     sndwnd:  15826
irs:  233567076  rcvnxt:  233567616  rcvwnd:      15845  delrcvwnd:    539

SRTT: 292 ms, RTTO: 359 ms, RTV: 67 ms, KRTT: 0 ms
minRTT: 12 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs
IP Precedence value : 6

Datagrams (max data segment is 1460 bytes):
Rcvd: 38 (out of order: 0), with data: 27, total data bytes: 539
Sent: 45 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 08

Table 1 describes the significant fields shown in the display. Fields that are preceded by the asterisk character are displayed only when the counter has a nonzero value.

Table 1 show ip bgp neighbors Field Descriptions 

Field
Description

BGP neighbor

IP address of the BGP neighbor and its autonomous system number.

remote AS

Autonomous-system number of the neighbor.

local AS 300 no-prepend (not shown in display)

Verifies that the local autonomous system number is not prepended to received external routes. This output supports the hiding of the local autonomous systems when migrating autonomous systems.

internal link

"internal link" is displayed for iBGP neighbors. "external link" is displayed for external BGP (eBGP) neighbors.

BGP version

BGP version being used to communicate with the remote router.

remote router ID

IP address of the neighbor.

BGP state

Finite state machine (FSM) stage of session negotiation.

up for

Time, in hhmmss, that the underlying TCP connection has been in existence.

Last read

Time, in hhmmss, since BGP last received a message from this neighbor.

last write

Time, in hhmmss, since BGP last sent a message to this neighbor.

hold time

Time, in seconds, that BGP will maintain the session with this neighbor without receiving a messages.

keepalive interval

Time, interval in seconds, that keepalive messages are transmitted to this neighbor.

Neighbor capabilities

BGP capabilities advertised and received from this neighbor. "advertised and received" is displayed when a capability is successfully exchanged between two routers.

Route Refresh

Status of the route refresh capability.

MPLS Label Capability

Indicates that MPLS labels are both sent and received by the eBGP peer.

Graceful Restart Capability

Status of the graceful restart capability.

Address family IPv4 Unicast

IP Version 4 unicast-specific properties of this neighbor.

Message statistics

Statistics organized by message type.

InQ depth is

Number of messages in the input queue.

OutQ depth is

Number of messages in the output queue.

Sent

Total number of transmitted messages.

Received

Total number of received messages.

Opens

Number of open messages sent and received.

notifications

Number of notification (error) messages sent and received.

Updates

Number of update messages sent and received.

Keepalives

Number of keepalive messages sent and received.

Route Refresh

Number of route refresh request messages sent and received.

Total

Total number of messages sent and received.

Default minimum time between...

Time, in seconds, between advertisement transmissions.

For address family:

Address family for which the following fields refer.

BGP table version

Internal version number of the table. This is the primary routing table with which the neighbor has been updated. The number increments when the table changes.

neighbor version

Number used by the software to track prefixes that have been sent and those that need to be sent.

...update-group

Number of update-group member for this address family.

Prefix activity

Prefix statistics for this address family.

Prefixes current

Number of prefixes accepted for this address family.

Prefixes total

Total number of received prefixes.

Implicit Withdraw

Number of times that a prefix has been withdrawn and readvertised.

Explicit Withdraw

Number of times that prefix is withdrawn because it is no longer feasible.

Used as bestpath

Number of received prefixes installed as a best paths.

Used as multipath

Number of received prefixes installed as multipaths.

* Saved (soft-reconfig)

Number of soft resets performed with a neighbor that supports soft reconfiguration. This field is displayed only if the counter has a nonzero value.

* History paths

This field is displayed only if the counter has a nonzero value.

* Invalid paths

Number of invalid paths. This field is displayed only if the counter has a nonzero value.

Local Policy Denied Prefixes

Prefixes denied due to local policy configuration. Counters are updated for inbound and outbound policy denials. The fields under this heading are displayed only if the counter has a nonzero value.

* route-map

Displays inbound and outbound route-map policy denials.

* filter-list

Displays inbound and outbound filter-list policy denials.

* prefix-list

Displays inbound and outbound prefix-list policy denials.

* Ext Community

Displays only outbound extended community policy denials.

* AS_PATH too long

Displays outbound AS-path length policy denials.

* AS_PATH loop

Displays outbound AS-path loop policy denials.

* AS_PATH confed info

Displays outbound confederation policy denials.

* AS_PATH contains AS 0

Displays outbound denials of AS 0.

* NEXT_HOP Martian

Displays outbound martian denials.

* NEXT_HOP non-local

Displays outbound non-local next-hop denials.

* NEXT_HOP is us

Displays outbound next-hop-self denials.

* CLUSTER_LIST loop

Displays outbound cluster-list loop denials.

* ORIGINATOR loop

Displays outbound denials of local originated routes.

* unsuppress-map

Displays inbound denials due to an unsuppress-map.

* advertise-map

Displays inbound denials due to an advertise-map.

* VPN Imported prefix

Displays inbound denials of VPN prefixes.

* Well-known Community

Displays inbound denials of well-known communities.

* SOO loop

Displays inbound denials due to site-of-origin.

* Bestpath from this peer

Displays inbound denials because the bestpath came from the local router.

* Suppressed due to dampening

Displays inbound denials because the neighbor or link is in a dampening state.

* Bestpath from iBGP peer

Deploys inbound denials because the bestpath came from an iBGP neighbor.

* Incorrect RIB for CE

Deploys inbound denials due to RIB errors for a CE router.

* BGP distribute-list

Displays inbound denials due to a distribute list.

Number of NLRIs...

Number of network layer reachability attributes in updates.

Connections established

Number of times a TCP and BGP connection have been successfully established.

dropped

Number of times that a valid session has failed or been taken down.

Last reset

Time since this peering session was last reset. The reason for the reset is displayed on this line.

External BGP neighbor may be... (not shown in the display)

Indicates that the BGP TTL security check is enabled. The maximum number hops that can separate the local and remote peer is displayed on this line.

Connection state

Connection status of the BGP peer.

Connection is ECN Disabled

Explicit congestion notification status (enabled or disabled).

Local host: 10.108.50.1, Local port: 179

IP address of the local BGP speaker. BGP port number 179.

Foreign host: 10.108.50.2, Foreign port: 42698

Neighbor address and BGP destination port number.

Enqueued packets for retransmit:

Packets queued for retransmission by TCP.

Event Timers

TCP event timers. Counters are provided for starts and wakeups (expired timers).

Retrans

Number of times a packet has been retransmitted.

TimeWait

Time waiting for the retransmission timers to expire.

AckHold

Acknowledgement hold timer.

SendWnd

Transmission (send) window.

KeepAlive

Number of keep alive packets.

GiveUp

Number times a packet is dropped due to no acknowledgement.

PmtuAger

Path MTU discovery timer.

DeadWait

Expiration timer for dead segments.

iss:

Initial packet transmission sequence number.

snduna:

Last transmission sequence number that has not been acknowledged.

sndnxt:

Next packet sequence number to be transmitted.

sndwnd:

TCP window size of the remote neighbor.

irs:

Initial packet receive sequence number.

rcvnxt:

Last receive sequence number that has been locally acknowledged.

rcvwnd:

TCP window size of the local host.

delrcvwnd:

Delayed receive window—data the local host has read from the connection, but has not yet subtracted from the receive window the host has advertised to the remote host. The value in this field gradually increases until it is larger than a full-sized packet, at which point it is applied to the rcvwnd field.

SRTT:

A calculated smoothed round-trip timeout.

RTTO:

Round-trip timeout.

RTV:

Variance of the round-trip time.

KRTT:

New round-trip timeout (using the Karn algorithm). This field separately tracks the round-trip time of packets that have been re-sent.

minRTT:

Smallest recorded round-trip timeout (hard-wire value used for calculation).

maxRTT:

Largest recorded round-trip timeout.

ACK hold:

Time the local host will delay an acknowledgment to carry (piggyback) additional data.

IP Precedence value:

IP precedence of the BGP packets.

Datagrams

Number of update packets received from a neighbor.

Rcvd:

Number of received packets.

with data

Number of update packets sent with data.

total data bytes

Total received in bytes.

Sent

Number of update packets sent.

Second Congestion

Number of update packets with data sent.

Datagrams: Rcvd

Number of update packets received from a neighbor.

out of order:

Number of packets received out of sequence.

with data

Number of update packets received with data.

Last reset

Elapsed time since this peering session was last reset.

unread input bytes

Number of bytes of packets still to be processed.

retransmit

Number of packets retransmitted.

fastretransmit

A duplicate acknowledgement is retransmitted for an out of order segment before the retransmission timer expires.

partialack

Number of retransmissions for partial acknowledgements (transmissions before or without subsequent acknowledgements).

Second Congestion

Second retransmission due to congestion.


show ip bgp neighbors advertised-routes: Example

The following example displays routes advertised for only the 172.16.232.178 neighbor:

Router# show ip bgp neighbors 172.16.232.178 advertised-routes 

BGP table version is 27, local router ID is 172.16.232.181
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network          Next Hop          Metric LocPrf Weight Path
*>i10.0.0.0      172.16.232.179         0    100      0 ?
*> 10.20.2.0     10.0.0.0                0         32768 i

Table 2 describes the significant fields shown in the display.

Table 2 show ip bgp neighbors advertised-routes Field Descriptions 

Field
Description

BGP table version

Internal version number of the table. This is the primary routing table with which the neighbor has been updated. The number increments when the table changes.

local router ID

IP address of the local BGP speaker.

Status codes

Status of the table entry. The status is displayed at the beginning of each line in the table. It can be one of the following values:

s—The table entry is suppressed.

d—The table entry is dampened and will not be advertised to BGP neighbors.

h—The table entry does not contain the best path based on historical information.

*—The table entry is valid.

>—The table entry is the best entry to use for that network.

i—The table entry was learned via an internal BGP (iBGP) session.

Origin codes

Origin of the entry. The origin code is placed at the end of each line in the table. It can be one of the following values:

i—Entry originated from Interior Gateway Protocol (IGP) and was advertised with a network router configuration command.

e—Entry originated from Exterior Gateway Protocol (EGP).

?—Origin of the path is not clear. Usually, this is a router that is redistributed into BGP from an IGP.

Network

IP address of a network entity.

Next Hop

IP address of the next system used to forward a packet to the destination network. An entry of 0.0.0.0 indicates that there are non-BGP routes in the path to the destination network.

Metric

If shown, this is the value of the inter-autonomous system metric. This field is not used frequently.

LocPrf

Local preference value as set with the set local-preference route-map configuration command. The default value is 100.

Weight

Weight of the route as set via autonomous system filters.

Path

Autonomous system paths to the destination network. There can be one entry in this field for each autonomous system in the path.


show ip bgp neighbors paths: Example

The following is example output from the show ip bgp neighbors command entered with the paths keyword:

Router# show ip bgp neighbors 172.29.232.178 paths ^10 

Address    Refcount Metric Path
0x60E577B0        2     40 10 ?

Table 3 describes the significant fields shown in the display.

Table 3 show ip bgp neighbors paths Field Descriptions

Field
Description

Address

Internal address where the path is stored.

Refcount

Number of routes using that path.

Metric

Multi Exit Discriminator (MED) metric for the path. (The name of this metric for BGP versions 2 and 3 is INTER_AS.)

Path

Autonomous system path for that route, followed by the origin code for that route.


show ip bgp neighbors received prefix-filter: Example

The following example shows that a prefix-list the filters all routes in the 10.0.0.0 network has be received from the 192.168.20.72 neighbor:

Router# show ip bgp neighbors 192.168.20.72 received prefix-filter

Address family:IPv4 Unicast
ip prefix-list 192.168.20.72:1 entries
   seq 5 deny 10.0.0.0/8 le 32

Table 4 describes the significant fields shown in the display.

Table 4 show ip bgp neighbors received prefix-filter Field Descriptions

Field
Description

Address family

Address family mode in which the prefix filter is received.

ip prefix-list

Prefix list sent from the specified neighbor.


show ip bgp neighbors policy: Example

The following sample output shows the policies applied to the neighbor at 192.168.1.2. The output displays both inherited policies and policies configured on the neighbor device. Inherited polices are policies that the neighbor inherits from a peer-group or a peer-policy template.

Router# show ip bgp neighbors 192.168.1.2 policy

Neighbor: 192.168.1.2, Address-Family: IPv4 Unicast
Locally configured policies:
 route-map ROUTE in
Inherited polices:
 prefix-list NO-MARKETING in
 route-map ROUTE in
 weight 300
 maximum-prefix 10000

Cisco IOS Release 12.0(31)S and 12.4(4)T: Example

The following is sample output from the show ip bgp neighbors command that verifies that BFD is being used to detect fast fallover for the BGP neighbor that is a BFD peer.

Router# show ip bgp neighbors

BGP neighbor is 172.16.10.2,  remote AS 45000, external link
.
.
.
 Using BFD to detect fast fallover

Cisco IOS Release 12.2(33)SRA: Example

The following is sample output from the show ip bgp neighbors command that verifies that BGP TCP path MTU discovery is enabled for the BGP neighbor at 172.16.1.2.

Router# show ip bgp neighbors 172.16.1.2

BGP neighbor is 172.16.1.2,  remote AS 45000, internal link
  BGP version 4, remote router ID 172.16.1.99
.
.
.
 For address family: IPv4 Unicast
  BGP table version 5, neighbor version 5/0
.
.
.
  Address tracking is enabled, the RIB does have a route to 172.16.1.2
  Address tracking requires at least a /24 route to the peer
  Connections established 3; dropped 2
  Last reset 00:00:35, due to Router ID changed
  Transport(tcp) path-mtu-discovery is enabled
.
.
.
SRTT: 146 ms, RTTO: 1283 ms, RTV: 1137 ms, KRTT: 0 ms
minRTT: 8 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: higher precedence, retransmission timeout, nagle, path mtu capable

Related Commands

Command
Description

neighbor send-label

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.

neighbor send-label explicit-null

Enables a BGP router to send MPLS labels with explicit-null information for a CSC-CE router and BGP routes to a neighboring CSC-PE router.


show ip bgp vpnv4

To display Virtual Private Network Version 4 (VPNv4) address information from the Border Gateway Protocol (BGP) table, use the show ip bgp vpnv4 command in user EXEC or privileged EXEC mode.

show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} [rib-failure] [ip-prefix/length [longer-prefixes]] [network-address [mask] [longer-prefixes]] [cidr-only] [community] [community-list] [dampened-paths] [filter-list] [flap-statistics] [inconsistent-as] [neighbors] [paths [line]] [peer-group] [quote-regexp] [regexp] [summary] [labels]

Syntax Description

all

Displays the complete VPNv4 database.

rd route-distinguisher

Displays Network Layer Reachability Information (NLRI) prefixes that match the named route distinguisher.

vrf vrf-name

Displays NLRI prefixes associated with the named VPN routing and forwarding (VRF) instance.

rib-failure

(Optional) Displays BGP routes that failed to install in the VRF table.

ip-prefix/length

(Optional) The IP prefix address (in dotted decimal format) and the length of the mask (0 to 32). The slash mark must be included.

longer-prefixes

(Optional) Displays the entry, if any, that exactly matches the specified prefix parameter and all entries that match the prefix in a "longest-match" sense. That is, prefixes for which the specified prefix is an initial substring.

network-address

(Optional) The IP address of a network in the BGP routing table.

mask

(Optional) The mask of the network address, in dotted decimal format.

cidr-only

(Optional) Displays only routes that have nonclassful net masks.

community

(Optional) Displays routes that match this community.

community-list

(Optional) Displays routes that match this community list.

dampened-paths

(Optional) Displays paths suppressed because of dampening (BGP route from peer is up and down).

filter-list

(Optional) Displays routes that conform to the filter list.

flap-statistics

(Optional) Displays flap statistics of routes.

inconsistent-as

(Optional) Displays only routes that have inconsistent autonomous systems of origin.

neighbors

(Optional) Displays details about TCP and BGP neighbor connections.

paths

(Optional) Displays path information.

line

(Optional) A regular expression to match the BGP autonomous system paths.

peer-group

(Optional) Displays information about peer groups.

quote-regexp

(Optional) Displays routes that match the autonomous system path regular expression.

regexp

(Optional) Displays routes that match the autonomous system path regular expression.

summary

(Optional) Displays BGP neighbor status.

labels

(Optional) Displays incoming and outgoing BGP labels for each NLRI prefix.


Command Modes

User EXEC (>)
Privileged EXEC (#)

Command History

Release
Modification

12.0(5)T

This command was introduced.

12.2(2)T

The output of the show ip bgp vpnv4 all ip-prefix command was enhanced to display attributes including multipaths and a best path to the specified network.

12.0(21)ST

The tags keyword was replaced by the labels keyword to conform to the MPLS guidelines. This command was integrated into Cisco IOS Release 12.0(21)ST.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.

12.2(13)T

This command was integrated into Cisco IOS Release 12.2(13)T.

12.0(27)S

The output of the show ip bgp vpnv4 all labels command was enhanced to display explicit-null label information.

12.3

The rib-failure keyword was added for VRFs.

12.2(22)S

The output of the show ip bgp vpnv4 vrf vrf-name labels command was modified so that directly connected VRF networks no longer display as aggregate; no label appears instead.

12.2(25)S

This command was updated to display MPLS VPN nonstop forwarding information.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB and implemented on the Cisco 10000 series router. The display output was modified to indicate whether BGP Nonstop Routing (NSR) with stateful switchover (SSO) is enabled and the reason the last BGP lost SSO capability.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA, and the output was modified to support per-VRF assignment of the BGP router ID.

12.2(31)SB2

The output was modified to support per-VRF assignment of the BGP router ID.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.


Usage Guidelines

Use this command to display VPNv4 information from the BGP database. The show ip bgp vpnv4 all command displays all available VPNv4 information. The show ip bgp vpnv4 summary command displays BGP neighbor status. The show ip bgp vpnv4 all labels command displays explicit-null label information.

Examples

The following example shows output for all available VPNv4 information in a BGP routing table:

Router# show ip bgp vpnv4 all

BGP table version is 18, local router ID is 10.14.14.14
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP,? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 1:101 (default for vrf vpn1)
*>i10.6.6.6/32       10.0.0.21              11    100      0 ?
*> 10.7.7.7/32       10.150.0.2             11         32768 ?
*>i10.69.0.0/30      10.0.0.21               0    100      0 ?
*> 10.150.0.0/24     10.0.0.0                 0         32768 ?

Table 5 describes the significant fields shown in the display.

Table 5 show ip bgp vpnv4 all Field Descriptions 

Field
Description

Network

Displays the network address from the BGP table.

Next Hop

Displays the address of the BGP next hop.

Metric

Displays the BGP metric.

LocPrf

Displays the local preference.

Weight

Displays the BGP weight.

Path

Displays the BGP path per route.


The following example shows how to display a table of labels for NLRI prefixes that have a route distinguisher value of 100:1.

Router# show ip bgp vpnv4 rd 100:1 labels

Network            Next Hop       In label/Out label
Route Distinguisher: 100:1 (vrf1)
   10.0.0.0         10.20.0.60      34/nolabel
   10.0.0.0         10.20.0.60      35/nolabel
   10.0.0.0         10.20.0.60      26/nolabel
                    10.20.0.60      26/nolabel
   10.0.0.0         10.15.0.15      nolabel/26

Table 6 describes the significant fields shown in the display.

Table 6 show ip bgp vpnv4 rd labels Field Descriptions 

Field
Description

Network

Displays the network address from the BGP table.

Next Hop

Specifies the BGP next hop address.

In label

Displays the label (if any) assigned by this router.

Out label

Displays the label assigned by the BGP next hop router.


The following example shows VPNv4 routing entries for the VRF named vpn1:

Router# show ip bgp vpnv4 vrf vpn1

BGP table version is 18, local router ID is 10.14.14.14
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP,? - incomplete
 
Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 1:101 (default for vrf vpn1)
*>i10.6.6.6/32       10.0.0.21              11    100      0 ?
*> 10.7.7.7/32       10.150.0.2             11         32768 ?
*>i10.69.0.0/30      10.0.0.21               0    100      0 ?
*> 10.150.0.0/24      10.0.0.0                0         32768 ?
*> 10.0.0.1/32       10.150.0.2             11         32768 ?
*>i10.0.0.3/32       10.0.0.21              11    100      0 ?

Table 7 describes the significant fields shown in the display.

Table 7 show ip bgp vpnv4 vrf Field Descriptions 

Field
Description

Network

Displays the network address from the BGP table.

Next Hop

Displays the address of the BGP next hop.

Metric

Displays the BGP metric.

LocPrf

Displays the local preference.

Weight

Displays the BGP weight.

Path

Displays the BGP path per route.


The following example shows attributes for network 10.22.22.0 that include multipaths and a best path:

Router# show ip bgp vpnv4 all 10.22.22.0

BGP routing table entry for 10:1:10.22.22.0/24, version 50
Paths:(6 available, best #1)
Multipath:iBGP
  Advertised to non peer-group peers:
  10.1.12.12 
  22
    10.22.7.8 (metric 11) from 10.11.3.4 (10.0.0.8)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath, best
      Extended Community:RT:100:1
      Originator:10.0.0.8, Cluster list:10.1.1.44
  22
    10.22.1.9 (metric 11) from 10.11.1.2 (10.0.0.9)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath
      Extended Community:RT:100:1
      Originator:10.0.0.9, Cluster list:10.1.1.22

Table 8 describes the significant fields shown in the display.

Table 8 show ip bgp vpnv4 all network-address Field Descriptions 

Field
Description

BGP routing table entry for ... version

Internal version number of the table. This number is incremented whenever the table changes.

Paths

Number of autonomous system paths to the specified network. If multiple paths exist, one of the multipaths is designated the best path.

Multipath

Indicates the maximum paths configured (iBGP or eBGP).

Advertised to non peer-group peers

IP address of the BGP peers to which the specified route is advertised.

10.22.7.8 (metric 11) from 10.11.3.4 (10.0.0.8)

Indicates the next hop address and the address of the gateway that sent the update.

Origin

Indicates the origin of the entry. It can be one of the following values:

IGP—Entry originated from Interior Gateway Protocol (IGP) and was advertised with a network router configuration command.

incomplete—Entry originated from other than an IGP or Exterior Gateway Protocol (EGP) and was advertised with the redistribute router configuration command.

EGP—Entry originated from an EGP.

metric

If shown, the value of the interautonomous system metric.

localpref

Local preference value as set with the set local-preference route-map configuration command. The default value is 100.

valid

Indicates that the route is usable and has a valid set of attributes.

internal/external

The field is internal if the path is learned via iBGP. The field is external if the path is learned via eBGP.

multipath

One of multiple paths to the specified network.

best

If multiple paths exist, one of the multipaths is designated the best path and this path is advertised to neighbors.

Extended Community

Route Target value associated with the specified route.

Originator

The router ID of the router from which the route originated when route reflector is used.

Cluster list

The router ID of all the route reflectors that the specified route has passed through.


The following example shows routes that BGP could not install in the VRF table:

Router# show ip bgp vpnv4 vrf xyz rib-failure

Network            Next Hop                      RIB-failure   RIB-NH Matches
Route Distinguisher: 2:2 (default for vrf bar)
10.1.1.2/32        10.100.100.100      Higher admin distance               No
10.111.111.112/32  10.9.9.9            Higher admin distance              Yes

Table 9 describes the significant fields shown in the display.

Table 9 show ip bgp vpnv4 vrf rib-failure Field Descriptions 

Field
Description

Network

IP address of a network entity.

Next Hop

IP address of the next system that is used when forwarding a packet to the destination network. An entry of 0.0.0.0 indicates that the router has some non-BGP routes to this network.

RIB-failure

Cause of the Routing Information Base (RIB) failure. Higher admin distance means that a route with a better (lower) administrative distance, such as a static route, already exists in the IP routing table.

RIB-NH Matches

Route status that applies only when Higher admin distance appears in the RIB-failure column and the bgp suppress-inactive command is configured for the address family being used. There are three choices:

Yes—Means that the route in the RIB has the same next hop as the BGP route or that the next hop recurses down to the same adjacency as the BGP next hop.

No—Means that the next hop in the RIB recurses down differently from the next hop of the BGP route.

n/a—Means that the bgp suppress-inactive command is not configured for the address family being used.


The following example shows the information displayed on the active and standby Route Processors when they are configured for MPLS VPN nonstop forwarding.

Active Route Processor

Router# show ip bgp vpnv4 all labels

Network         Next Hop   In label/Out label
Route Distinguisher: 100:1 (vpn1)
10.12.12.12/32  10.0.0.0    16/aggregate(vpn1)
10.0.0.0/8      10.0.0.0    17/aggregate(vpn1)
Route Distinguisher: 609:1 (vpn0)
10.13.13.13/32  10.0.0.0    18/aggregate(vpn0)

Router# show ip bgp vpnv4 vrf vpn1 labels

Network          Next Hop   In label/Out label
Route Distinguisher: 100:1 (vpn1)
10.12.12.12/32   10.0.0.0    16/aggregate(vpn1)
10.0.0.0/8       10.0.0.0    17/aggregate(vpn1)

Standby Route Processor

Router# show ip bgp vpnv4 all labels

Network       Masklen   In label 
Route Distinguisher: 100:1
10.12.12.12   /32       16
10.0.0.0      /8        17
Route Distinguisher: 609:1
10.13.13.13   /32       18

Router# show ip bgp vpnv4 vrf vpn1 labels

Network        Masklen   In label 
Route Distinguisher: 100:1
10.12.12.12    /32       16
10.0.0.0       /8        17 

Table 10 describes the significant fields shown in the display.

Table 10 show ip bgp vpn4 labels Field Descriptions 

Field
Description

Network

The network address from the BGP table.

Next Hop

The BGP next hop address.

In label

The label (if any) assigned by this router.

Out label

The label assigned by the BGP next hop router.

Masklen

The mask length of the network address.


The following example displays output, including the explicit-null label, from the show ip bgp vpnv4 all labels command on a CSC-PE router:

Router# show ip bgp vpnv4 all labels

   Network          Next Hop      In label/Out label
Route Distinguisher: 100:1 (v1)
   10.0.0.0/24       10.0.0.0        19/aggregate(v1)
   10.0.0.1/32       10.0.0.0        20/nolabel
   10.1.1.1/32       10.0.0.0        21/aggregate(v1)
   10.10.10.10/32    10.0.0.1        25/exp-null 
   10.168.100.100/32
                     10.0.0.1        23/exp-null
   10.168.101.101/32
                     10.0.0.1        22/exp-null

Table 11 describes the significant fields shown in the display.

Table 11 show ip bgp vpnv4 all labels Field Descriptions 

Field
Description

Network

Displays the network address from the BGP table.

Next Hop

Displays the address of the BGP next hop.

In label

Displays the label (if any) assigned by this router.

Out label

Displays the label assigned by the BGP next hop router.

Route Distinguisher

Displays an 8-byte value added to an IPv4 prefix to create a VPN IPv4 prefix.


The following example displays separate router IDs for each VRF in the output from an image in Cisco IOS Release 12.2(33)SRA, 12.2(31)SB2 and later releases with the Per-VRF Assignment of BGP Router ID feature configured. The router ID is shown next to the VRF name.

Router# show ip bgp vpnv4 all

BGP table version is 5, local router ID is 172.17.1.99
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 1:1 (default for vrf vrf_trans) VRF Router ID 10.99.1.2
*> 192.168.4.0      10.0.0.0                  0         32768 ?
Route Distinguisher: 42:1 (default for vrf vrf_user) VRF Router ID 10.99.1.1
*> 192.168.5.0      10.0.0.0                  0         32768 ?

Table 12 describes the significant fields shown in the display.

Table 12 show ip bgp vpnv4 all (VRF Router ID) Field Descriptions 

Field
Description

Route Distinguisher

Displays an 8-byte value added to an IPv4 prefix to create a VPN IPv4 prefix.

vrf

Name of the VRF.

VRF Router ID

Router ID for the VRF.


Related Commands

Command
Description

show ip vrf

Displays the set of defined VRFs and associated interfaces.


show mpls forwarding-table

To display the contents of the Multiprotocol Label Switching (MPLS) Label Forwarding Information Base (LFIB), use the show mpls forwarding-table command in privileged EXEC mode.

show mpls forwarding-table [network {mask | length} | labels label [- label] | interface interface | next-hop address | lsp-tunnel [tunnel-id]] [vrf vrf-name] [detail]

Syntax Description

network

(Optional) Destination network number.

mask

IP address of the destination mask whose entry is to be shown.

length

Number of bits in the mask of the destination.

labels label - label

(Optional) Displays only entries with the specified local labels.

interface interface

(Optional) Displays only entries with the specified outgoing interface.

next-hop address

(Optional) Displays only entries with the specified neighbor as the next hop.

lsp-tunnel

(Optional) Displays only entries with the specified label switched path (LSP) tunnel, or with all LSP tunnel entries.

tunnel-id

(Optional) Specifies the LSP tunnel for which to display entries.

vrf vrf-name

(Optional) Displays only entries with the specified VPN routing and forwarding (VRF) instance.

detail

(Optional) Displays information in long form (includes length of encapsulation, length of MAC string, maximum transmission unit (MTU), and all labels).


Command Modes

Privileged EXEC (#)

Command History

Release
Modification

11.1CT

This command was introduced.

12.1(3)T

This command was updated with MPLS terminology and command syntax.

12.2(8)T

The command was modified to accommodate use of the MPLS experimental (EXP) level as a selection criterion for packet forwarding. The output display was modified to include a bundle adjacency field and exp (vcd) values when the optional detail keyword is specified.

12.0(22)S

IPv6 MPLS aggregate label and prefix information was added to the display.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.0(27)S

The command output was modified to include explicit-null label information.

12.2(25)S

The output was changed in the following ways:

The term "tag" was replaced with the term "label."

The term "untagged" was replaced with the term "no label."

12.0(29)S

This command was integrated into Cisco IOS Release 12.0(29)S.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB and implemented on the Cisco 10000 series routers.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.


Examples

The following is sample output from the show mpls forwarding-table command:

Router# show mpls forwarding-table

Local Outgoing      Prefix            Bytes label Outgoing       Next Hop       
Label Label or VC   or Tunnel Id      switched  interface                     
26    No Label      10.253.0.0/16     0         Et4/0/0       10.27.32.4    
28    1/33          10.15.0.0/16      0         AT0/0.1       point2point    
29    Pop Label     10.91.0.0/16      0         Hs5/0         point2point    
      1/36          10.91.0.0/16      0         AT0/0.1       point2point    
30    32            10.250.0.97/32    0         Et4/0/2       10.92.0.7      
      32            10.250.0.97/32    0         Hs5/0         point2point    
34    26            10.77.0.0/24      0         Et4/0/2       10.92.0.7      
      26            10.77.0.0/24      0         Hs5/0         point2point    
35    No Label[T]   10.100.100.101/32 0         Tu301         point2point    
36    Pop Label     10.1.0.0/16      0         Hs5/0         point2point    
      1/37          10.1.0.0/16      0         AT0/0.1       point2point    

[T]     Forwarding through a TSP tunnel.
        View additional labeling info with the 'detail' option

The following is sample output from the show mpls forwarding-table command when the IPv6 Provider Edge Router over MPLS feature is configured to allow IPv6 traffic to be transported across an IPv4 MPLS backbone. The labels are aggregated because there are several prefixes for one local label, and the prefix column contains "IPv6" instead of a target prefix.

Router# show mpls forwarding-table

Local Outgoing      Prefix            Bytes label Outgoing       Next Hop       
Label Label or VC   or Tunnel Id      switched  interface                     
16    Aggregate     IPv6              0             
17    Aggregate     IPv6              0                 
18    Aggregate     IPv6              0                 
19    Pop Label     192.168.99.64/30  0         Se0/0         point2point    
20    Pop Label     192.168.99.70/32  0         Se0/0         point2point      
21    Pop Label     192.168.99.200/32 0         Se0/0         point2point    
22    Aggregate     IPv6              5424    
23    Aggregate     IPv6              3576 
24    Aggregate     IPv6              2600

The following is sample output from the show mpls forwarding-table command when you specify the detail keyword. If the MPLS EXP level is used as a selection criterion for packet forwarding, a bundle adjacency exp (vcd) field is included in the display. This field includes the EXP value and the corresponding virtual circuit descriptor (VCD) in parentheses. The line in the output that reads "No output feature configured" indicates that the MPLS egress NetFlow accounting feature is not enabled on the outgoing interface for this prefix.

Router# show mpls forwarding-table detail

Local Outgoing      Prefix            Bytes label Outgoing       Next Hop       
label   label or VC     or Tunnel Id      switched  interface                     
16    Pop label       10.0.0.6/32        0         AT1/0.1       point2point 
  Bundle adjacency exp(vcd)
  0(1) 1(1) 2(1) 3(1) 4(1) 5(1) 6(1) 7(1)
  MAC/Encaps=12/12, MTU=4474, label Stack{}
      00010000AAAA030000008847
  No output feature configured
17    18            10.0.0.9/32        0         AT1/0.1       point2point    
  Bundle adjacency exp(vcd)
  0(1) 1(1) 2(1) 3(1) 4(1) 5(1) 6(1) 7(1)
  MAC/Encaps=12/16, MTU=4470, label Stack{18}
      00010000AAAA030000008847 00012000
  No output feature configured
18    19            10.0.0.10/32        0        AT1/0.1       point2point    
  Bundle adjacency exp(vcd)
  0(1) 1(1) 2(1) 3(1) 4(1) 5(1) 6(1) 7(1)
  MAC/Encaps=12/16, MTU=4470, label Stack{19}
      00010000AAAA030000008847 00013000
  No output feature configured
19    17            10.0.0.0/8         0        AT1/0.1       point2point    
  Bundle adjacency exp(vcd)
  0(1) 1(1) 2(1) 3(1) 4(1) 5(1) 6(1) 7(1)
  MAC/Encaps=12/16, MTU=4470, label Stack{17}
      00010000AAAA030000008847 00011000
  No output feature configured
20    20            10.0.0.0/8         0        AT1/0.1       point2point    
  Bundle adjacency exp(vcd)
  0(1) 1(1) 2(1) 3(1) 4(1) 5(1) 6(1) 7(1)
  MAC/Encaps=12/16, MTU=4470, label Stack{20}
      00010000AAAA030000008847 00014000
  No output feature configured
21    Pop label       10.0.0.0/24        0        AT1/0.1       point2point 
  Bundle adjacency exp(vcd)
  0(1) 1(1) 2(1) 3(1) 4(1) 5(1) 6(1) 7(1)
  MAC/Encaps=12/12, MTU=4474, label Stack{}
      00010000AAAA030000008847
  No output feature configured
22    Pop label       10.0.0.4/32         0        Et2/3         10.0.0.4 
  MAC/Encaps=14/14, MTU=1504, label Stack{}
      000427AD10430005DDFE043B8847
  No output feature configured

The following is sample output from the show mpls forwarding-table command when you use the detail keyword. In this example, the MPLS egress NetFlow accounting feature is enabled on the first three prefixes, as indicated by the line in the output that reads "Feature Quick flag set."

Router# show mpls forwarding-table detail

Local  Outgoing    Prefix            Bytes label  Outgoing   Next Hop
label    label or VC   or Tunnel Id      switched   interface
16     Aggregate   10.0.0.0/8[V]     0
        MAC/Encaps=0/0, MTU=0, label Stack{}
        VPN route: vpn1
        Feature Quick flag set
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 
17     No label    10.0.0.0/8[V]      0          Et0/0/2    10.0.0.1
        MAC/Encaps=0/0, MTU=1500, label Stack{}
        VPN route: vpn1
        Feature Quick flag set
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
18     No label    10.42.42.42/32[V] 4185       Et0/0/2    10.0.0.1
        MAC/Encaps=0/0, MTU=1500, label Stack{}
        VPN route: vpn1
        Feature Quick flag set
Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
19     2/33        10.41.41.41/32    0          AT1/0/0.1  point2point
        MAC/Encaps=4/8, MTU=4470, label Stack{2/33(vcd=2)}
        00028847 00002000
        No output feature configured

Cisco 10000 Series Examples

The following is sample output from the show mpls forwarding-table command:

Router# show mpls forwarding-table

Local   Outgoing      Prefix            Bytes Label   Outgoing   Next Hop
Label   Label or VC   or Tunnel Id      Switched      interface
16      Pop Label     10.0.0.0/8        0             Fa1/0/0    10.0.0.2
        Pop Label     10.0.0.0/8        0             Fa1/1/0    10.0.0.2
17      Aggregate     10.0.0.0/8[V]     570           vpn2
21      Pop Label     10.11.11.11/32    0             Fa1/0/0    10.0.0.2
22      Pop Label     10.12.12.12/32    0             Fa1/1/0    10.0.0.2
23      No Label      10.3.0.0/16[V]     0             Fa4/1/0   10.0.0.2

The following is Cisco 10000 series sample output from the show mpls forwarding-table command when you specify the detail keyword:

Router# show mpls forwarding-table detail

Local   Outgoing      Prefix            Bytes Label   Outgoing   Next Hop
Label   Label or VC   or Tunnel Id      Switched      interface
16      Pop Label     10.0.0.0/8        0             Fa1/0/0    10.0.0.2
        MAC/Encaps=14/14, MRU=1500, Label Stack{}
        000B45C93889000B45C930218847
        No output feature configured
        Pop Label     10.0.0.0/8        0             Fa1/1/0     10.0.0.2
        MAC/Encaps=14/14, MRU=1500, Label Stack{}
        000B45C92881000B45C930288847
        No output feature configured
17      Aggregate    10.0.0.0/8[V]      570           vpn2
        MAC/Encaps=0/0, MRU=0, Label Stack{}
        VPN route: vpn2
        No output feature configured
21      Pop Label     10.11.11.11/32     0            Fa1/0/0     10.0.0.2
        MAC/Encaps=14/14, MRU=1500, Label Stack{}
       000B45C93889000B45C930218847
       No output feature configured

Table 13 describes the significant fields shown in the displays.

Table 13 show mpls forwarding-table Field Descriptions 

Field
Description

Local label

Label assigned by this router.

Outgoing Label or VC

Note VC is not applicable to the Cisco 10000 series routers.

Label assigned by the next hop or virtual path identifier (VPI)/virtual channel identifier (VCI) used to get to next hop. The entries in this column include the following:

Note VPI and VCI are not applicable to the Cisco 10000 series routers.

[T]—Means forwarding through an LSP tunnel.

No Label—Means that there is no label for the destination from the next hop or that label switching is not enabled on the outgoing interface.

Pop Label—Means that the next hop advertised an implicit NULL label for the destination and that the router popped the top label.

Aggregate—Means there are several prefixes for one local label. This entry is used when IPv6 is configured on edge routers to transport IPv6 traffic over an IPv4 MPLS network.

Note IPv6 traffic is not applicable to the Cisco 10000 series routers.

Prefix or Tunnel Id

Address or tunnel to which packets with this label are sent.

Note If IPv6 is configured on edge routers to transport IPv6 traffic over an IPv4 MPLS network, "IPv6" is displayed here.

Bytes Label Switched

Number of bytes switched with this incoming label.

Outgoing interface

Interface through which packets with this label are sent.

Next Hop

IP address of the neighbor that assigned the outgoing label.

Bundle adjacency exp(vcd)

Bundle adjacency information. Includes the MPLS EXP value and the corresponding VCD.

MAC/Encaps

Length in bytes of the Layer 2 header and length in bytes of the packet encapsulation, including the Layer 2 header and label header.

MTU

MTU of the labeled packet.

Label Stack

All the outgoing labels. If the outgoing interface is transmission convergence (TC)-ATM, the VCD is also shown.

Note TC-ATM is not applicable to the Cisco 10000 series routers.

00010000AAAA030000008847 00013000

The actual encapsulation in hexadecimal form. A space is shown between Layer 2 and the label header.


Explicit-Null Label Example

The following example shows output, including the explicit-null label = 0 (commented in bold), from the show mpls forwarding-table command on a CSC-PE router:

Router# show mpls forwarding-table 

Local  Outgoing      Prefix            Bytes label  Outgoing   Next Hop    
label  label or VC   or Tunnel Id      switched     interface              
17     Pop label     10.10.0.0/32      0            Et2/0      10.10.0.1      
18     Pop label     10.10.10.0/24     0            Et2/0      10.10.0.1      
19     Aggregate     10.10.20.0/24[V]  0                                  
20     Pop label     10.10.200.1/32[V] 0            Et2/1      10.10.10.1      
21     Aggregate     10.10.1.1/32[V]   0                                  
22     0             192.168.101.101/32[V]   \
                                       0            Et2/1      192.168.101.101      
23     0             192.168.101.100/32[V]   \
                                       0            Et2/1      192.168.101.100      
25     0             192.168.102.125/32[V] 0        Et2/1      192.168.102.125 !outlabel 
value 0

Table 14 describes the significant fields shown in the display.

Table 14 show mpls forwarding-table Field Descriptions 

Field
Description

Local label

Label assigned by this router.

Outgoing label or VC

Label assigned by the next hop or VPI/VCI used to get to next hop. The entries this column include the following:

[T]—Means forwarding through an LSP tunnel.

No label—Means that there is no label for the destination from the next hop or that label switching is not enabled on the outgoing interface.

Pop label—Means that the next hop advertised an implicit NULL label for the destination and that this router popped the top label.

Aggregate—Means there are several prefixes for one local label. Used when IPv6 is configured on edge routers to transport IPv6 traffic over an IPv4 MPLS network.

0—Means the explicit null label value = 0.

Prefix or Tunnel Id

Address or tunnel to which packets with this label are going.

Note If IPv6 is configured on edge routers to transport IPv6 traffic over an IPv4 MPLS network, IPv6 is displayed here.

Bytes label switched

Number of bytes switched with this incoming label.

Outgoing interface

Interface through which packets with this label are sent.

Next Hop

IP address of the neighbor that assigned the outgoing label.


Related Commands

Command
Description

neighbor send-label

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.

neighbor send-label explicit-null

Enables a BGP router to send MPLS labels with explicit-null information for a CSC-CE router and BGP routes to a neighboring CSC-PE router.


Feature Information for MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

Table 15 lists the release history for this feature.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform. Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.


Note Table 15 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.


Table 15 Feature Information for MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

Feature Name
Releases
Feature Information

MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session

12.0(27)S
12.0(27)S1
12.2(28)SB
12.2(33)SRA
12.2(33)SXH

The MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session feature provides a method to advertise explicit null in a BGP label session for a carrier supporting carrier (CSC) customer edge (CE) router.

In 12.0(27)S, this feature was introduced.

In 12.0(27)S1, support was added for the Cisco 12000 series Internet routers.

In 12.2(28)SB, support was added for the Cisco 10000 series router.

This feature was integrated into Cisco IOS Release 12.2(33)SRA.

This feature was integrated into Cisco IOS Release 12.2(33)SXH.


Glossary

BGP—Border Gateway Protocol. The exterior Border Gateway Protocol used to exchange routing information between routers in separate autonomous systems. BGP uses Transmission Control Protocol (TCP). Because TCP is a reliable protocol, BGP does not experience problems with dropped or fragmented data packets.

CE router—customer edge router. A router on the border between a VPN provider and a VPN customer that belongs to the customer.

BGP—external Border Gateway Protocol. A BGP session between routers in different autonomous systems. When a pair of routers in different autonomous systems are more than one IP hop away from each other, an external BGP session between those two routers is called multihop external BGP.

label—A short, fixed-length data identifier that tells switching nodes how to forward data (packets or cells).

label distribution—The techniques and processes used to cause routed traffic to travel through the network on a path other than the one that would have been chosen if standard routing methods had been used.

LDP—Label Distribution Protocol. The protocol that supports MPLS hop-by-hop forwarding by distributing bindings between labels and network prefixes. The Cisco proprietary version of this protocol is the Tag Distribution Protocol (TDP).

LSP—label-switched path. A configured connection between two routers, in which MPLS is used to carry packets. A path created by the concatenation of one or more label switched hops, allowing a packet to be forwarded by swapping labels from an MPLS node to another MPLS node.

MPLS—Multiprotocol Label Switching. A method for directing packets primarily through Layer 2 switching rather than Layer 3 routing. In MPLS, packets are assigned short, fixed-length labels at the ingress to an MPLS cloud by using the concept of forwarding equivalence classes. Within the MPLS domain, the labels are used to make forwarding decisions mostly without recourse to the original packet headers; formerly known as tag switching.

NLRI—Network Layer Reachability Information. BGP sends routing update messages containing NLRI, which describes the route. In this context, an NLRI is a prefix. A BGP update message carries one or more NLRI prefixes and the attributes of a route for the NLRI prefixes. The route attributes include a BGP next hop gateway address, community values, and other information.

PE router—provider edge router. A router on the border between a VPN provider and a VPN customer that belongs to the provider.

QoS—quality of service. A measure of performance for a transmission system that reflects its transmission quality and service availability.

router—A network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information.

VPN—Virtual Private Network. A secure IP-based network that shares resources on one or more physical networks. A VPN contains geographically dispersed sites that can communicate securely over a shared backbone.