OSPF Support for Forwarding Adjacencies over MPLS TE Tunnels

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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Prerequisites for OSPF Forwarding Adjacency

  • OSPF must be configured in your network.

  • Cisco Express Forwarding (CEF) must be enabled.

  • You should understand MPLS TE tunnels for forwarding adjacency as described in the " MPLS Traffic Engineering Forwarding Adjacency" module.

Information About OSPF Forwarding Adjacency

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

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

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

Related Documents

Related Topic

Document Title

Configuring OSPF

"Configuring OSPF"

OSPF commands

Cisco IOS IP Routing: OSPF Command Reference

Cisco IOS master command list, all releases

Cisco IOS Master Command List, All Releases

Standards

Standard

Title

None

--

MIBs

MIB

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 software releases, and feature sets, use Cisco MIB Locator found at the following URL:

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

RFCs

RFC

Title

RFC 3137

OSPF Stub Router Advertisement

Technical Assistance

Description

Link

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http://www.cisco.com/cisco/web/support/index.html