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
Glossary
MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session
The MPLS VPN—Explicit Null Label Support with Border Gateway Protocol (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.
History for MPLS VPN—Explicit Null Label Support with BGP IPv4 Label Session Feature
|
Release
|
Modification
|
12.0(27)S |
This feature was introduced. |
12.2(27)SBA |
This feature was integrated into Cisco IOS Release 12.2(27)SBA. |
Note 
Software images for Cisco 12000 series Internet routers have been deferred to Cisco IOS Release 12.0(27)S1.
Finding Support Information for Platforms and Cisco IOS Software Images
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.
Contents
•Prerequisites 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
•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 (QoS)
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
5. neighbor ip-address send-label explicit-null
6. neighbor {ip-address | peer-group-name} 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 automous-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
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 3.0.0.2 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} 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 [neighbor-address] [received-routes | routes | advertised-routes | {paths regexp} | dampened-routes | received prefix-filter]]
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 [neighbor-address] [received-routes | routes | advertised-routes | {paths regexp} | dampened-routes | received prefix-filter]]
Example:
Router# show ip bgp neighbors |
Displays information about the TCP and BGP connections to neighbors including explicit null. •The optional neighbor-address argument displays the address of the neighbor whose routes you have learned If you omit this argument, all neighbors are displayed. •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. •The optional advertised-routes keyword displays all the routes the router has advertised to the neighbor. •The optional paths regexp keyword argument combination is a regular expression that is used to match the paths received. •The optional dampened-routes keyword displays the dampened routes to the neighbor at the IP address specified. •The optional received prefix-filter keyword displays the configured prefix list filter for the specified IP address. |
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 3.0.0.2 send-label explicit-null
neighbor 3.0.0.2 remote-as 200
neighbor 3.0.0.2 activate
neighbor 3.0.0.2 send-label explicit-null
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, automous number, 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 1.0.0.2, remote AS 300, external link
BGP version 4, remote router ID 72.72.72.72
BGP state = Established, up for 00:45:16
Last read 00:00:16, hold time is 180, keepalive interval is 60 seconds
Route refresh: advertised and received(new)
Address family IPv4 Unicast: advertised and received
ipv4 MPLS Label capability: advertised and received
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
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
Prefix activity: ---- ----
Prefixes Current: 3 3 (Consumes 144 bytes)
Additional References
The following sections provide references related to MPLS—VPN Explicit Null Label with BGP IPv4 Label Session.
Related Documents
|
Related Topic
|
Document Title
|
BGP configuration tasks |
Network Protocols Command Reference, Part 1 |
IPv4 BGP label distribution |
MPLS VPN—InterAS—IPv4 BGP Label Distribution
MPLS VPN—Carrier Supporting Carrier—IPv4 BGP Label Distribution |
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 Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content. |
http://www.cisco.com/techsupport |
Command Reference
This section documents new or modified commands only.
New Commands
•neighbor send-label explicit-null
Modified Commands
•debug ip bgp
•show ip bgp neighborsdebug ip bgp
•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]
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. |
Defaults
No default behavior or values
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, and the mpls keyword was added. |
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 command output was modified to show explicit-null label information. |
12.2(27)SBA |
This command was integrated into Cisco IOS Release 12.2(27)SBA. |
Usage Guidelines
Use this command with the updates and mpls keywords to display explicit-null label information.
Examples
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
01:33:53: BGP(0): route 36.36.36.36/32 up
01:33:53: BGP(0): nettable_walker 36.36.36.36/32 route sourced locally
01:33:53: BGP: adding MPLS label to 36.36.36.36/32
01:33:53: BGP: check on 36.36.36.36/32 in LDP - ok
01:33:53: BGP: label imp-null allocated via LDP
01:33:53: BGP-IPv4: send exp-null label for 36.36.36.36/32
01:33:53: BGP-IPv4: Send prefix 36.36.36.36/32, label exp-null !explicit-null label
being sent
01:33:53: BGP(0): 1.0.0.2 send UPDATE (format) 36.36.36.36/32, next 1.0.0.1, metric 0,
path , mpls label 0 !label value is 0
01:33:53: BGP(0): updgrp 1 - 1.0.0.2 enqueued 1 updates, average/maximum size (bytes)
61/61
Related Commands
|
Command
|
Description
|
show debug |
Displays active debug output. |
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. |
Defaults
This command is not enabled by default.
Command Modes
Address family configuration
Router configuration
Command History
|
Release
|
Modification
|
12.0(27)S |
This command was introduced. |
12.2(27)SBA |
This command was integrated into Cisco IOS Release 12.2(27)SBA. |
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 1.0.0.2 remote-as 300
Router(config-router)# address-family ipv4
Router(config-router-af)# neighbor 1.0.0.2 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 1.0.0.1 remote-as 100
Router(config-router)# address-family ipv4 vrf v1
Router(config-router-af)# neighbor 1.0.0.1 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 the Transmission Control Protocol (TCP) and Border Gateway Protocol (BGP) connections to neighbors, use the show ip bgp neighbors command in EXEC mode.
show ip bgp neighbors [neighbor-address] [received-routes | routes | advertised-routes | {paths regexp} | dampened-routes | received prefix-filter]]
Syntax Description
neighbor-address |
(Optional) Address of the neighbor from whose routes you have learned. If you omit this argument, all neighbors are displayed. |
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. This is a subset of the output from the received-routes keyword. |
advertised-routes |
(Optional) Displays all the routes the router has advertised to the neighbor. |
paths regexp |
(Optional) Regular expression that is used to match the paths received. |
dampened-routes |
(Optional) Displays the dampened routes to the neighbor at the IP address specified. |
received prefix-filter |
(Optional) Displays the configured prefix list filter for the specified IP address. |
Defaults
No default behavior or values
Command Modes
EXEC
Command History
|
Release
|
Modification
|
10.0 |
This command was introduced. |
11.2 |
The received-routes keyword was added |
12.2(4)T |
The received prefix-filter keyword was added. |
12.2(8)T |
The no-prepend configuration option was added to the display output. |
12.0(21)ST |
This command was updated to display MPLS label information. |
12.0(22)S |
This command was integrated into Cisco IOS Release 12.0(22)S. Support for the Cisco 12000 series routers (Engine 0 and Engine 2) was added. The received prefix-filter keyword was added. The command output was modified to show BGP graceful restart capability. |
12.2(15)T |
The command output was modified to show BGP graceful restart capability. |
12.0(27)S |
The command output was modified to show BGP advertising explicit-null configuration. |
12.2(27)SBA |
This command was integrated into Cisco IOS Release 12.2(27)SBA. |
Usage Guidelines
Use this command to display explicit-null label information.
Examples
The following example shows output, including the explicit-null label, from the show ip bgp neighbors command on a CSC-CE router:
Router# show ip bgp neighbors
BGP neighbor is 1.0.0.2, remote AS 300, external link
BGP version 4, remote router ID 72.72.72.72
BGP state = Established, up for 01:38:38
Last read 00:00:37, hold time is 180, keepalive interval is 60 seconds
Route refresh: advertised and received(new)
Address family IPv4 Unicast: advertised and received
ipv4 MPLS Label capability: advertised and received
Default minimum time between advertisement runs is 30 seconds
For address family: IPv4 Unicast
BGP table version 11, neighbor version 11/0
Output queue sizes : 0 self, 0 replicated
Index 1, Offset 0, Mask 0x2
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 configuration set
Prefix activity: ---- ----
Prefixes Current: 3 3 (Consumes 144 bytes)
Local Policy Denied Prefixes: -------- -------
Suppressed duplicate: 0 3
Bestpath from this peer: 3 n/a
Number of NLRIs in the update sent: max 0, min 0
Connections established 1; dropped 0
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Local host: 1.0.0.1, Local port: 11000
Foreign host: 1.0.0.2, Foreign port: 179
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Event Timers (current time is 0x5C52FC):
Timer Starts Wakeups Next
iss: 1758035101 snduna: 1758037249 sndnxt: 1758037249 sndwnd: 15697
irs: 904214079 rcvnxt: 904216204 rcvwnd: 15738 delrcvwnd: 646
SRTT: 300 ms, RTTO: 607 ms, RTV: 3 ms, KRTT: 0 ms
minRTT: 0 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: higher precedence, nagle
Datagrams (max data segment is 1460 bytes):
Rcvd: 136 (out of order: 0), with data: 103, total data bytes: 2124
Sent: 187 (retransmit: 0, fastretransmit: 0), with data: 105, total data bytes: 2147
Table 1 describes the significant fields shown in the display.
Table 1 show ip bgp neighbors Field Descriptions
|
Field
|
Description
|
BGP neighbor |
IP address of the BGP neighbor and its autonomous system number. If the neighbor is in the same autonomous system as the router, then the link between them is internal; otherwise, it is considered external. |
remote AS |
Autonomous system of the neighbor. |
external link |
Indicates that this peer is an External Border Gateway Protocol (EBGP) peer. |
BGP version |
BGP version being used to communicate with the remote router; the router ID (an IP address) of the neighbor is also specified. |
remote router ID |
IP address of the neighbor. |
BGP state = Established |
Internal state of this BGP connection. |
up for |
Amount of time, in seconds, that the underlying TCP connection has been in existence. |
Last read |
Time that BGP last read a message from this neighbor. |
hold time |
Maximum amount of time that can elapse between messages from the peer. |
keepalive interval |
Time period, in seconds, between sending keepalive packets, which help ensure that the TCP connection is up. |
Neighbor capabilities |
BGP capabilities advertised and received from this neighbor. |
Route refresh |
The status of route refresh. Advertised and received is displayed when route refresh has successfully occurred between two routers. |
Address family IPv4 Unicast |
IP Version 4 unicast-specific properties of this neighbor. |
ipv4 MPLS Label capability |
Indicates that IPv4 MPLS labels are both sent and received by the EBGP peer. |
Message statistics |
Number and type of messages. |
InQ depth is 0 |
Size of the inbound queue. |
OutQ depth is 0 |
Size of the outbound queue. |
Sent |
Total number of BGP messages that have been sent to this peer. |
Rcvd |
Total number of BGP messages that have been received from this peer. |
Opens |
Total number of messages sent each time a connection is established. |
Notifications |
Total number of error messages sent to and received from this peer. |
Updates |
Total number of update messages sent to and received from this peer. |
Keepalives |
Total number of keepalive messages sent to and received from this peer. |
Route refresh |
Total number of route messages sent to and received from this peer. |
Total |
Total number of all types of messages sent to and received from this peer. |
Default minimum time between advertisement runs |
Value of minimum advertisement interval. |
For address family: IPv4 Unicast |
Address family to which the following fields refer. |
BGP table version |
Indicates that the neighbor has been updated with this version of the primary BGP routing table. |
neighbor version |
Number used by the software to track the prefixes that have been sent and those that must be sent to this neighbor. |
Sending Prefix & Label |
Indicates that the EBGP peer sends MPLS labels with the capability of advertising explicit null labels for directly connected routes. |
Sent |
Total number and type of prefixes that have been sent to this peer. |
Rcvd |
Total number and type of prefixes that have been received from this peer. |
Prefixes Current |
Total number of current prefixes sent to and received from this peer. |
Prefixes Total |
Total number of all prefixes set to and received from this peer. |
Used as bestpath |
Total number of prefixes used as best path. |
Used as multipath |
Total number of prefixes used as multipath. |
Connections established |
Number of times the router has established a TCP connection and the two peers have agreed to speak BGP with each other. |
dropped |
Number of times that a good connection has failed or been taken down. |
Last reset never |
Elapsed time since this peering session was last reset. |
Connection state |
State of BGP peer. |
unread input bytes |
Number of bytes of packets still to be processed. |
Local host, Local port |
Peering address of local router, plus port. |
Foreign host, Foreign port |
Peering address of the neighbor. |
Enqueued packets for retransmits |
Packets waiting to be retransmitted. |
Event Timers |
Table displays the name of the timer and the number of starts and wakeups for each one. |
Retrans |
The number of starts and wakeups for the Retransmission timer. |
TimeWait |
The number of starts and wakeups for the TimeWait timer. |
AckHold |
The number of starts and wakeups for the AcknowledgmentHold timer. |
SendWnd |
The number of starts and wakeups for the SendWnd timer. |
KeepAlive |
The number of starts and wakeups for the KeepAlive timer. |
GiveUp |
The number of starts and wakeups for the GiveUp timer. |
PmtuAger |
The number of starts and wakeups for the PmtuAger timer. |
DeadWait |
The number of starts and wakeups for the DeadWait timer. |
iss |
Initial send sequence number. |
snduna |
Last send sequence number the local host sent but has not received an acknowledgment. |
sndnxt |
Sequence number the local host will send next. |
sndwnd |
TCP window size of the remote host. |
irs |
Initial receive sequence number. |
rcvnxt |
Last receive sequence number the local host has 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 that 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 delays an acknowledgment in order to piggyback data on it. |
Flags |
IP precedence of the BGP packets. |
Datagrams: Rcvd |
Number of update packets received from a neighbor. |
with data |
Number of update packets received with data. |
total data bytes |
Total bytes of data. |
Sent |
Number of update packets sent. |
with data |
Number of update packets with data sent. |
total data bytes |
Total number of data bytes. |
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 (VPN) address information from the Border Gateway Protocol (BGP) table, use the show ip bgp vpnv4 command in EXEC mode.
show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} [ip-prefix/length [longer-prefixes] [output-modifiers]] [network-address [mask] [longer-prefixes] [output-modifiers]] [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 have a matching route distinguisher. |
vrf vrf-name |
Displays NLRI prefixes associated with the named VPN routing and forwarding instance (VRF). |
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. |
output-modifiers |
(Optional) For a list of associated keywords and arguments, use context-sensitive help. |
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 nonnatural net masks. |
community |
(Optional) Displays routes matching this community. |
community-list |
(Optional) Displays routes matching this community list. |
dampened-paths |
(Optional) Displays paths suppressed on account of dampening (BGP route from peer is up and down). |
filter-list |
(Optional) Displays routes conforming 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 matching the autonomous system path "regular expression." |
regexp |
(Optional) Displays routes matching the autonomous system path regular expression. |
summary |
(Optional) Displays BGP neighbor status. |
labels |
(Optional) Displays incoming and outgoing BGP labels for each NLRI prefix. |
Defaults
No default behavior or values
Command Modes
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/length command was enhanced to display attributes including multipaths and a best path to the specified network. |
12.0(21)ST |
The keyword tags was replaced with the keyword labels to conform to the MPLS IETF guidelines. This command was integrated into Cisco IOS Release 12.0(21)ST. |
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 command output was modified to include explicit-null label information. |
12.2(27)SBA |
This command was integrated into Cisco IOS Release 12.2(27)SBA. |
Usage Guidelines
Use this command with the keywords all and labels to display explicit-null label information.
Examples
The following example shows output, including the explicit-null label, from the show ip bgp neighbors 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)
1.0.0.0/24 0.0.0.0 19/aggregate(v1)
1.0.0.1/32 0.0.0.0 20/nolabel
1.1.1.1/32 0.0.0.0 21/aggregate(v1)
36.36.36.36/32 1.0.0.1 25/exp-null !Label value exp-null
Table 2 describes the significant fields shown in the display.
Table 2 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. |
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 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 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 |
(Optional) IP address of the destination mask whose entry is to be shown. |
length |
(Optional) Number of bits in mask of 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 tunnel-id |
(Optional) Displays only entries with the specified label switched path (LSP) tunnel, or with all LSP tunnel entries. |
vrf vrf-name |
(Optional) Displays only entries with the specified VPN routing/forwarding instance (VRF). |
detail |
(Optional) Displays information in long form (includes length of encapsulation, length of MAC string, maximum transmission unit (MTU), and all labels). |
Defaults
No default behavior or values
Command Modes
EXEC
Command History
|
Release
|
Modification
|
11.1 CT |
This command was introduced. |
12.1(3)T |
This command was modified to reflect new MPLS Internet Engineering Task Force (IETF) terminology and command-line interface (CLI) command syntax. |
12.2(8)T |
The command was modified to accommodate use of the MPLS experimental (EXP) level as a selection criteria 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(27)SBA |
This command was integrated into Cisco IOS Release 12.2(27)SBA. |
Usage Guidelines
Use this command to display explicit-null label information.
Examples
The following example shows output, including the explicit-null label = 0, from the show mpls forwarding-table command on a CSC-PE router:
Router# show mpls forwarding-table
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
17 Pop tag 34.34.34.34/32 0 Et2/0 3.0.0.2
18 Pop tag 4.0.0.0/24 0 Et2/0 3.0.0.2
19 Aggregate 1.0.0.0/24[V] 0
20 Pop tag 1.0.0.1/32[V] 0 Et2/1 1.0.0.1
21 Aggregate 1.1.1.1/32[V] 0
22 0 101.101.101.101/32[V] \
23 0 100.100.100.100/32[V] \
25 0 36.36.36.36/32[V] 0 Et2/1 1.0.0.1 !outlabel value 0
Table 3 describes the significant fields shown in the display.
Table 3 show mpls forwarding-table Field Descriptions
|
Field
|
Description
|
Local tag |
Label assigned by this router. |
Outgoing tag or VC |
Label assigned by the next hop or virtual path identifier (VPI)/virtual channel identifier (VCI) used to get to next hop. The entries that you can specify in this column include the following: •[T]—Means forwarding through an LSP tunnel. •Untagged—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 tag—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 tag 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. |
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.
EBGP—External Border Gateway Protocol. A BGP session between routers in different autonomous systems (ASs). When a pair of routers in different ASs 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.
Note Refer to the Internetworking Terms and Acronyms for terms not included in this glossary.
Copyright © 2005 Cisco Systems, Inc. All rights reserved.
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