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The NSF/SSO--MPLS VPN feature allows a provider edge (PE) router to preserve data forwarding information in a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) when the primary Route Processor (RP) restarts. This module describes how to enable nonstop forwarding (NSF) in a basic MPLS VPN network.
Tag Distribution Protocol (TDP) sessions are not supported. Only Label Distribution Protocol (LDP) sessions are supported.
The NSF/SSO--MPLS VPN feature cannot be configured on label-controlled ATM (LC-ATM) interfaces.
VPN NSF requires several elements in order to work:
VPN NSF uses the BGP Graceful Restart mechanisms to create MPLS forwarding entries for VPNv4 prefixes in NSF mode. The forwarding entries are preserved during a restart. BGP also saves prefix and corresponding label information and recovers the information after a restart.
The NSF/SSO--MPLS VPN feature also uses NSF for the label distribution protocol in the core network (either MPLS Label Distribution Protocol, traffic engineering, or static labeling).
The NSF/SSO--MPLS VPN feature uses NSF for the Interior Gateway Protocol (IGP) used in the core (OSPF or IS-IS).
The NSF/SSO--MPLS VPN feature uses NSF for the routing protocols between the PE and CE routers.
When BGP allocates local labels for prefixes, it checkpoints the local label binding in the backup RP. The checkpointing function copies state information from the active RP to the backup RP, thereby ensuring that the backup RP has an identical copy of the latest information. If the active RP fails, the backup RP can take over with no interruption in service. Checkpointing begins when the active RP does a bulk synchronization, which copies all of the local label bindings to the backup RP. After that, the active RP dynamically checkpoints individual prefix label bindings when a label is allocated or freed. This allows forwarding of labeled packets to continue before BGP reconverges.
When a BGP Graceful Restart-capable router loses connectivity, it performs the following actions as the restarting router:
The restarting router establishes BGP sessions with other routers and relearns the BGP routes from other routers that are also capable of Graceful Restart. The restarting router waits to receive updates from the neighboring routers. When the neighboring routers send end-of-Routing Information Base (RIB) markers to indicate that they are done sending updates, the restarting router starts sending its own updates.
The restarting router accesses the checkpoint database to find the label that was assigned for each prefix. If it finds the label, it advertises it to the neighboring router. If it does not find the label, it allocates a new label and advertises it.
The restarting router removes any stale prefixes after a timer for stale entries expires.
A BGP Graceful Restart-capable peer router performs the following actions when it encounters a restarting router:
The peer router sends all the routing updates to the restarting router. When it has finished sending updates, the peer router sends an end-of-RIB marker to the restarting router.
The peer router does not immediately remove the BGP routes learned from the restarting router from its BGP routing table. As it learns the prefixes from the restarting router, the peer refreshes the stale routes if the new prefix and label information matches the old information.
If a router is not configured for the NSF/SSO--MPLS VPN feature and it attempts to establish a BGP session with a router that is configured with the NSF/SSO--MPLS VPN feature, the two routers create a normal BGP session but do not have the ability to perform the NSF/SSO--MPLS VPN feature.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
ip cef [distributed ] Example: |
Enables Cisco Express Forwarding.
|
|
Step 4 |
router bgp autonomous-system-number Example: |
Configures a BGP routing process and enters router configuration mode. |
|
Step 5 |
bgp graceful-restart Example: |
Enables BGP Graceful Restart on the router. |
|
Step 6 |
bgp graceful-restart restart-time seconds Example: |
(Optional) Specifies the maximum time to wait for a graceful-restart-capable neighbor to come back up after a restart. |
|
Step 7 |
bgp graceful-restart stalepath-time seconds Example: |
(Optional) Specifies the maximum time to hold on to the stale paths of a gracefully restarted peer. All stale paths are deleted after the expiration of this timer. |
|
Step 8 |
end Example: |
Exits to privileged EXEC mode. |
|
Step 1 |
show ip bgp vpnv4 all labels This command displays incoming and outgoing BGP labels for each route distinguisher. The following is sample output from the command: Example: |
|
Step 2 |
show ip bgp vpnv4 all neighbors This command displays whether the BGP peers are capable of Graceful Restart. The following is sample output from the command: Example: |
|
Step 3 |
show ip bgp labels This command displays information about MPLS labels in the Exterior Border Gateway Protocol (EBGP) route table. The following is sample output from the command: Example: |
|
Step 4 |
show ip bgp neighbors This command displays whether the BGP peers are capable of Graceful Restart. The following is sample output from the command: Example: |
The following sample output shows the configuration of the NSF/SSO--MPLS VPN feature on the CE and PE routers. SSO is enabled by default, and LDP is the default MPLS label protocol.
ip cef
no ip domain-lookup
!
interface Loopback0
ip address 10.10.10.10 255.255.255.255
!
interface GigabitEthernet1/0/4
ip address 10.0.0.1 255.0.0.0
media-type 10BaseT
!
router ospf 100
redistribute bgp 101
nsf enforce global
passive-interface GigabitEthernet1/0/4
network 10.0.0.0 0.255.255.255 area 100
!
router bgp 101
no synchronization
bgp graceful-restart restart-time 120
bgp graceful-restart stalepath-time 360
bgp graceful-restart network 10.0.0.0
network 10.0.0.0
neighbor 10.0.0.2 remote-as 100
redundancy
mode sso
!
ip cef distributed
mpls ldp graceful-restart
mpls label protocol ldp
ip vrf vpn1
rd 100:1
route-target export 100:1
route-target import 100:1
no mpls aggregate-statistics
!
interface Loopback0
ip address 10.12.12.12 255.255.255.255
!
interface GigabitEthernet1/0/4
ip vrf forwarding vpn1
ip address 10.0.0.2 255.0.0.0
!
mpls ip
interface ATM3/0/0
no ip address
!
interface ATM3/0/0.1 point-to-point
ip unnumbered Loopback0
mpls ip
!
router ospf 100
passive-interface GigabitEthernet1/0/4
nsf enforce global
network 10.0.0.0 0.255.255.255 area 100
!
router bgp 100
no synchronization
bgp graceful-restart restart-time 120
bgp graceful-restart stalepath-time 360
bgp graceful-restart
no bgp default ipv4-unicast
neighbor 10.14.14.14 remote-as 100
neighbor 10.14.14.14 update-source Loopback0
!
address-family ipv4 vrf vpn1
neighbor 10.0.0.1 remote-as 101
neighbor 10.0.0.1 activate
exit-address-family
!
address-family vpnv4
neighbor 10.14.14.14 activate
neighbor 10.14.14.14 send-community extended
exit-address-family
redundancy
mode sso
!
ip cef distributed
mpls ldp graceful-restart
mpls label protocol ldp
!
ip vrf vpn1
rd 100:1
route-target export 100:1
route-target import 100:1
no mpls aggregate-statistics
!
!
interface Loopback0
ip address 10.14.14.14 255.255.255.255
!
interface ATM1/0
no ip address
!
interface ATM1/0.1 point-to-point
ip unnumbered Loopback0
mpls ip
!
interface FastEthernet3/0/0
ip vrf forwarding vpn1
ip address 10.0.0.1 255.0.0.0
ip route-cache distributed
!
router ospf 100
nsf enforce global
passive-interface FastEthernet3/0/0
network 10.0.0.0 0.255.255.255 area 100
!
router bgp 100
no synchronization
bgp graceful-restart restart-time 120
bgp graceful-restart stalepath-time 360
bgp graceful-restart
no bgp default ipv4-unicast
neighbor 10.12.12.12 remote-as 100
neighbor 10.12.12.12 update-source Loopback0
!
address-family ipv4 vrf vpn1
neighbor 10.0.0.2 remote-as 102
neighbor 10.0.0.2 activate
exit-address-family
!
address-family vpnv4
neighbor 10.12.12.12 activate
neighbor 10.12.12.12 send-community extended
exit-address-family
ip cef
!
interface Loopback0
ip address 10.13.13.13 255.255.255.255
!
interface FastEthernet0/1
ip address 10.0.0.2 255.0.0.0
no ip mroute-cache
!
router ospf 100
redistribute bgp 102
nsf enforce global
passive-interface FastEthernet0/1
network 10.0.0.0 0.255.255.255 area 100
!
router bgp 102
no synchronization
bgp graceful-restart restart-time 120
bgp graceful-restart stalepath-time 360
bgp graceful-restart
network 10.0.0.0
network 10.0.0.0
neighbor 10.0.0.1 remote-as 100The following sections provide references related to the MPLS High Availability feature.
|
Related Topic |
Document Title |
|---|---|
|
MPLS VPNs Non Stop Forwarding |
NSF/SSO—MPLS VPN |
|
MPLS LDP Non Stop Forwarding |
NSF/SSO—MPLS LDP and LDP Graceful Restart |
|
AToM Non Stop Forwarding |
NSF/SSO: Any Transport over MPLS and Graceful Restart |
|
Cisco Express Forwarding |
Cisco Express Forwarding: Command Changes |
|
MIBs |
|
|
NSF/SSO |
Cisco Nonstop Forwarding MPLS High Availability: Command Changes |
|
Standard |
Title |
|---|---|
|
draft-ietf-mpls-bgp-mpls-restart.txt |
Graceful Restart Mechanism for BGP with MPLS |
|
draft-ietf-mpls-idr-restart.txt |
Graceful Restart Mechanism for BGP |
|
MIB |
MIBs Link |
|---|---|
|
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
|
RFC |
Title |
|---|---|
|
RFC 3478 |
Graceful Restart Mechanism for Label Distribution |
|
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. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. If you have a valid service contract but do not have a user ID or password, you can register on Cisco.com. |
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 |
|---|---|---|
|
NSF/SSO--MPLS VPN |
Cisco IOS XE Release 2.1 |
This feature allows a provider edge router to preserve data forwarding information in a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) when the primary Route Processor restarts. |
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