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Book Contents
- MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses
- MPLS VPN Inter-AS with ASBRs Exchanging IPv4 Routes and MPLS Labels
- MPLS VPN Multipath Support for Inter-AS VPNs
- MPLS VPN--Inter-AS Option AB
- MPLS VPN Carrier Supporting Carrier Using LDP and an IGP
- MPLS VPN Carrier Supporting Carrier with BGP
- MPLS VPN Load Balancing Support for Inter-AS and CSC VPNs
- MPLS VPN eBGP Multipath Support for CSC and Inter-AS MPLS VPNs
- MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
Find Matches in This Book Log in to Save Content Available Languages Download Options MPLS: Layer 3 VPNs: Inter-AS and CSC Configuration Guide, Cisco IOS Release 15S Chapter Title View with Adobe Reader on a variety of devices View in various apps on iPhone, iPad, Android, Sony Reader, or Windows Phone
Book Title
MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
Results
Contents
- MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
- 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 the Explicit Null Configuration
- Configuration Examples for MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
- Example: Configuring CSC-CE with BGP
- Example: Verifying the Explicit Null Configuration
- Additional References for MPLS VPN Explicit Null Label with BGP IPv4 Label Session
- Feature Information for MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
- Glossary
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) device.
- 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 for MPLS VPN Explicit Null Label with BGP IPv4 Label Session
- 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
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
On a carrier supporting carrier (CSC) customer edge (CE) device (CSC-CE) with Border Gateway Protocol (BGP) IPv4 label distribution, BGP advertises an implicit null label for directly connected routes. This causes the previous hop (penultimate) device to do penultimate hop popping (PHP).
The MPLS VPN Explicit Null Label Support BGP IPv4 Label Session feature makes the penultimate device swap the incoming label for (or impose) the explicit null label. This action forces the egress device 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
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 carrier supporting carrier (CSC) customer edge (CE) destination.
How to Configure MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
Configuring CSC with BGP
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} activate
7. end
DETAILED STEPS
Verifying the Explicit Null Configuration
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
Configuration Examples for MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
Example: Configuring CSC-CE with BGP
In the following example, the carrier supporting carrier (CSC) is configured with the Border Gateway Protocol (BGP) to distribute labels and to advertise explicit null for all its connected routes:
neighbor 10.0.0.0 send-label explicit-nullrouter 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
Example: Verifying the Explicit Null Configuration
In this example, the show ip bgp neighbors command displays information about connected Border Gateway Protocol (BGP) neighbors, including IP addresses, version numbers, neighbor capabilities, message statistics, and address family statistics that show if explicit null is configured:
Device# 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 advertisem*nt 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 for MPLS VPN Explicit Null Label with BGP IPv4 Label Session
Related Documents
Related Topic | Document Title |
---|---|
Cisco IOS commands | Cisco IOS Master Commands List, All Releases |
MPLS commands | Cisco IOS Multiprotocol Label Switching Command Reference |
BGP configuration tasks | IP Routing: BGP Configuration Guide |
BGP commands | Cisco IOS IP Routing: BGP Command Reference |
RFCs
RFC | 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 and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. | http://www.cisco.com/cisco/web/support/index.html |
Feature Information for MPLS VPN Explicit Null Label Support with BGP IPv4 Label Session
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
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(27)SBA 12.2(33)SRA 12.2(33)SXH Cisco IOS XE Release 2.3 | 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) device. 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(27)SBA, 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. In Cisco IOS XE Release 2.3, support was added for the Cisco ASR 1000 Series Routers. The following commands were introduced or modified: debug ip bgp, neighbor send-label explicit-null, show ip bgp neighbors, show ip bgp vpnv4, show mpls forwarding-table |
Glossary
- BGP
-
Border Gateway Protocol. The exterior Border Gateway Protocol used to exchange routing information between devices in separate autonomous systems. BGP uses TCP. Because TCP is a reliable protocol, BGP does not experience problems with dropped or fragmented data packets.
- CE device
-
customer edge device. A device 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 devices in different autonomous systems. When a pair of devices in different autonomous systems are more than one IP hop away from each other, an external BGP session between those two devices 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 devices, 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 device
-
provider edge device. A device 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.