OSPF Support for Forwarding Adjacencies over MPLS TE Tunnels

Last Updated: June 24, 2011

The OSPF Support for Forwarding Adjacencies over MPLS Traffic Engineered Tunnels feature adds Open Shortest Path First (OSPF) support to the Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Forwarding Adjacency feature, which allows a network administrator to handle a traffic engineering, label-switched path (LSP) tunnel as a link in an Interior Gateway Protocol (IGP) network based on the shortest path first (SPF) algorithm. An OSPF forwarding adjacency can be created between routers in the same area.

History for the OSPF Support for Forwarding Adjacencies over MPLS Traffic Engineered Tunnels Feature

Release

Modification

12.0(24)S

This feature was introduced.

12.2(25)S

This feature was integrated into Cisco IOS Release 12.2(25)S.

12.2(18)SXE

This feature was integrated into Cisco IOS Release 12.2(18)SXE.

12.2(27)SBC

This feature was integrated into Cisco IOS Release 12.2(27)SBC.

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Contents

Prerequisites for OSPF Forwarding Adjacency

Information About OSPF Forwarding Adjacency

Before you configure the OSPF Forwarding Adjacency feature, you should understand the concept described in this section.

Benefits of OSPF Forwarding Adjacency

OSPF includes MPLS TE tunnels in the OSPF link-state database in the same way that other links appear for purposes of routing and forwarding traffic. When an MPLS TE tunnel is configured between networking devices, that link is considered a forwarding adjacency. The user can assign a cost to the tunnel to indicate the link’s preference. Other networking devices will see the tunnel as a link in addition to the physical link.

How to Configure OSPF Forwarding Adjacency

This section contains the following procedure:

Configuring OSPF Forwarding Adjacency

This section describes how to configure the OSPF Forwarding Adjacency feature. You must configure a forwarding adjacency on two LSP tunnels bidirectionally, from A to B and B to A. Otherwise, the forwarding adjacency is advertised, but not used in the IGP network.

For the configuration to work, you need to set up a loopback interface with a 32-bit mask, enable CEF, enable MPLS traffic engineering, and set up a routing protocol (OSPF) for the MPLS network.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip cef distributed

4.    mpls traffic-eng tunnels

5.    interface loopback number

6.    ip address ip-address mask

7.    no shutdown

8.    exit

9.    interface tunnel number

10.    tunnel mode mpls traffic-eng

11.    tunnel mpls traffic-eng forwarding-adjacency {holdtime value}

12.    ip ospf cost cost

13.    exit

14.    router ospf process-id

15.    mpls traffic-eng router-id interface

16.    mpls traffic-eng area number

17.    end


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
ip cef distributed


Example:

Router(config)# ip cef distributed

 

Enables Cisco Express Forwarding (CEF).

 
Step 4
mpls traffic-eng tunnels


Example:

Router(config)# mpls traffic-eng tunnels

 

Enables MPLS traffic engineering tunnel signaling on a device.

 
Step 5
interface loopback number


Example:

Router(config)# interface loopback0

 

Configures a loopback interface and enters interface configuration mode.

 
Step 6
ip address ip-address mask


Example:

Router(config-if)# ip address 10.1.1.1 255.255.255.255

 

Configures the IP address and subnet mask of the loopback interface.

 
Step 7
no shutdown


Example:

Router(config-if)# no shutdown

 

Enables the interface.

 
Step 8
exit


Example:

Router(config-if)# exit

 

Exits interface configuration mode.

 
Step 9
interface tunnel number


Example:

Router(config)# interface tunnel 1

 

Designates a tunnel interface for the forwarding adjacency and enters interface configuration mode.

 
Step 10
tunnel mode mpls traffic-eng


Example:

Router(config-if)# tunnel mode mpls traffic-eng

 

Sets the mode of a tunnel to MPLS for traffic engineering.

 
Step 11
tunnel mpls traffic-eng forwarding-adjacency {holdtime value}


Example:

Router(config-if)# tunnel mpls traffic-eng forwarding-adjacency holdtime 10000

 

Advertises a TE tunnel as a link in an IGP network.

  • The holdtime value keyword argument combination is the time in milliseconds (ms) that a TE tunnel waits after going down before informing the network. The range is 0 to 4,294,967,295 ms. The default value is 0.
 
Step 12
ip ospf cost cost


Example:

Router(config-if)# ip ospf cost 4

 

(Optional) Configures the cost metric for a tunnel interface to be used as a forwarding adjacency.

 
Step 13
exit


Example:

Router(config-if)# exit

 

Exits interface configuration mode.

 
Step 14
router ospf process-id


Example:

Router(config)# router ospf 1

 

Configures an OSPF routing process and enters router configuration mode.

 
Step 15
mpls traffic-eng router-id interface


Example:

Router(config-router)# mpls traffic-eng router-id ethernet 1/0

 

Specifies that the traffic engineering router identifier for the node is the IP address associated with a given interface.

 
Step 16
mpls traffic-eng area number


Example:

Router(config-router)# mpls traffic-eng area 1

 

Configures a router running OSPF MPLS so that it floods traffic engineering for the indicated OSPF area.

 
Step 17
end


Example:

Router(config-router)# end

 

Exits router configuration mode.

 

Configuration Examples for OSPF Forwarding Adjacency

This section contains an example of configuring OSPF forwarding adjacency:

OSPF Forwarding Adjacency Example

In the following example, the tunnel destination is the loopback interface on the other router. The router is configured with OSPF TE extensions and it floods traffic engineering link-state advertisements (LSAs) in OSPF area 0. The traffic engineering router identifier for the node is the IP address associated with Loopback 0. The last five lines of the example set up the routing protocol for the MPLS network, which is OSPF in this case.


Note
Do not use the mpls traffic-eng autoroute announce command if you configure a forwarding adjacency in the tunnel. 
ip routing
ip cef distributed
mpls traffic-eng tunnels
!
interface Loopback0
 ip address 127.0.0.1 255.255.255.255
 no shutdown
!
interface Tunnel1
 ip unnumbered Loopback0
 no ip directed-broadcast
 tunnel destination 10.1.1.1
 tunnel mode mpls traffic-eng
 tunnel mpls traffic-eng forwarding-adjacency holdtime 10000
 ip ospf cost 4
 tunnel mpls traffic-eng priority 2 2
 tunnel mpls traffic-eng bandwidth  10
 tunnel mpls traffic-eng path-option 2 dynamic
router ospf 5
 log-adjacency-changes
 network 10.1.1.1 0.0.0.0 area 0
 mpls traffic-eng router-id loopback0
 mpls traffic-eng area 0

When you look at the self-generated router LSA, you will see it as one of the links in router LSA (shown in bold in the following output).

Router# show ip ospf database route self-originate
OSPF Router with ID (10.5.5.5) (Process ID 5)
                Router Link States (Area 0)
  LS age:332
  Options:(No TOS-capability, DC)
  LS Type:Router Links
  Link State ID:10.5.5.5
  Advertising Router:10.5.5.5
  LS Seq Number:80000004
  Checksum:0x1D24
  Length:72
  Number of Links:4
    Link connected to another Router (point-to-point)
     (Link ID) Neighboring Router ID:10.3.3.3
     (Link Data) Router Interface address:0.0.0.23
      Number of TOS metrics:0
       TOS 0 Metrics:1562 
    Link connected to:a Transit Network
     (Link ID) Designated Router address:172.16.0.1
     (Link Data) Router Interface address:172.16.0.2
      Number of TOS metrics:0
       TOS 0 Metrics:10
    Link connected to:a Transit Network
     (Link ID) Designated Router address:172.16.0.3
     (Link Data) Router Interface address:172.16.0.4
      Number of TOS metrics:0
       TOS 0 Metrics:10
    Link connected to:a Stub Network
     (Link ID) Network/subnet number:10.5.5.5
     (Link Data) Network Mask:255.255.255.255
      Number of TOS metrics:0
       TOS 0 Metrics:1

Additional References

The following sections provide references related to OSPF Forwarding Adjacency.

Related Documents

Related Topic

Document Title

MPLS traffic engineering forwarding adjacency

MPLS Traffic Engineering Forwarding Adjacency

Configuring OSPF for MPLS traffic engineering

MPLS Traffic Engineering and Enhancements

MPLS Traffic Engineering - LSP Attributes

MPLS Traffic Engineering - LSP Attributes

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