Vol I - MPLS Traffic Engineering - Explicit PE to PE Tunnels Lab

Hi all,

I'm having trouble understanding how path-option under TE tunnel works. Here is my case 

- Create 2 path-option: 1 dynamic & 1 explicit

Rack1R3#sho run int tu34  
Building configuration...

Current configuration : 321 bytes
!
interface Tunnel34
 ip unnumbered Loopback0
 tunnel destination 150.1.4.4
 tunnel mode mpls traffic-eng
 tunnel mpls traffic-eng autoroute announce
 tunnel mpls traffic-eng priority 6 6
 tunnel mpls traffic-eng path-option 5 explicit name R3->R4
 tunnel mpls traffic-eng path-option 10 dynamic
 no routing dynamic
end

Rack1R3#sho ip explicit
PATH R3->R4 (strict source route, path complete, generation 7)
    1: next-address 150.1.13.1
    2: next-address 150.1.12.2
    3: next-address 150.1.25.5
    4: next-address 150.1.45.4
    5: next-address 150.1.4.4

- R3 uses explicit path after configuration

Rack1R3#sho mpls tr tu tu34

Name: Rack1R3_t34                         (Tunnel34) Destination: 150.1.4.4
  Status:
    Admin: up         Oper: up     Path: valid       Signalling: connected

    path option 5, type explicit R3->R4 (Basis for Setup, path weight 4)
    path option 10, type dynamic

  Config Parameters:
    Bandwidth: 0        kbps (Global)  Priority: 6  6   Affinity: 0x0/0xFFFF
    Metric Type: TE (default)
    AutoRoute:  enabled   LockDown: disabled  Loadshare: 0        bw-based
    auto-bw: disabled

  InLabel  :  -
  OutLabel : Serial1/2, 27
  RSVP Signalling Info:
       Src 150.1.3.3, Dst 150.1.4.4, Tun_Id 34, Tun_Instance 58
    RSVP Path Info:
      My Address: 150.1.3.3  
      Explicit Route: 150.1.13.1 150.1.12.1 150.1.12.2 150.1.25.5
                      150.1.45.4 150.1.4.4
      Record Route:  NONE
      Tspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits
    RSVP Resv Info:
      Record Route:  NONE
      Fspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits
  Shortest Unconstrained Path Info:
    Path Weight: 3 (TE)
    Explicit Route: 150.1.13.1 150.1.12.1 150.1.12.2 150.1.24.4
                    150.1.4.4
  History:
    Tunnel:
      Time since created: 4 hours, 46 minutes
      Time since path change: 16 seconds
    Current LSP:
      Uptime: 16 seconds
    Prior LSP:
      ID: path option 10 [57]
      Removal Trigger: path option removed

- Shutdown interface 150.1.25.5 on R5, R3 changes to use the dynamic path

Rack1R3#sho mpls tr tu tu34

Name: Rack1R3_t34                         (Tunnel34) Destination: 150.1.4.4
  Status:
    Admin: up         Oper: up     Path: valid       Signalling: connected

    path option 10, type dynamic (Basis for Setup, path weight 3)
    path option 5, type explicit R3->R4

  Config Parameters:
    Bandwidth: 0        kbps (Global)  Priority: 6  6   Affinity: 0x0/0xFFFF
    Metric Type: TE (default)
    AutoRoute:  enabled   LockDown: disabled  Loadshare: 0        bw-based
    auto-bw: disabled

  InLabel  :  -
  OutLabel : Serial1/2, 25
  RSVP Signalling Info:
       Src 150.1.3.3, Dst 150.1.4.4, Tun_Id 34, Tun_Instance 60
    RSVP Path Info:
      My Address: 150.1.3.3  
      Explicit Route: 150.1.13.1 150.1.12.1 150.1.12.2 150.1.24.4
                      150.1.4.4
      Record Route:  NONE
      Tspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits
    RSVP Resv Info:
      Record Route:  NONE
      Fspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits
  Shortest Unconstrained Path Info:
    Path Weight: 3 (TE)
    Explicit Route: 150.1.13.1 150.1.12.1 150.1.12.2 150.1.24.4
                    150.1.4.4
  History:
    Tunnel:
      Time since created: 4 hours, 48 minutes
      Time since path change: 4 seconds
    Current LSP:
      Uptime: 4 seconds
      Selection: reoptimation
    Prior LSP:
      ID: path option 5 [58]
      Removal Trigger: path error
      Last Error: PCALC:: Can't use link 150.1.25.5 on node 150.1.5.5

- However, when I bring up the interface 150.1.25.5 on R5 again, R3 do not switch back to the explicit path although its preference is lower

My questions are:

1. Can MPLS TE Tunnel switch back to use the explicit path if the explicit path is available?

2. If not, how can we force MPLS TE to do that?

Thanks

 

 

Comments

  • Hi,

     

    There you need the MPLS TE reoptimization so that the tunnel will come back to your desire path:

     

    There are multiple type of MPLS TE reoptimization called:

    1. Periodic reoptimization (command # mpls traffic-eng reoptimize timer frequency)

    2. Event-driven (command # mpls traffic-eng reoptimize event link-up)

    3. Manual reoptimization

     

    for more information you can search on cisco... or Traffic engineering with MPLS book...

    regards

    Dev

  • <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">






    1.  Yes, it can absolutely switch
    back.

     

    2.  You can force it, or it can happen
    automatically!

     

    Now that the short answers are done, let's talk about
    how.  It's called a "reoptimize timer".

     

    You can, from the exec prompt, type "mpls traffic-eng
    reoptimize" if you want to manually do it.

     

    Or, in global config mode, you can use "mpls traffic-eng
    reoptimize timers frequency (#sec)" to set the timers.  Default is 3600
    seconds or one hour.

     

    HTH,

     




    Scott Morris, CCIE4 #4713, JNCIE-M #153, JNCIS-ER, CISSP, et al.
    CCSI/JNCI-M/JNCI-ER
    Senior CCIE Instructor

    <?xml:namespace
    prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />[email protected]

     

    <?xml:namespace prefix = o ns =
    "urn:schemas-microsoft-com:office:office" />
    Internetwork Expert, Inc.
    http://www.InternetworkExpert.com
    Toll
    Free: 877-224-8987
    Outside US: 775-826-4344
    Online Community:
    http://tinyurl.com/6dmnsu
    CCIE Blog:
    http://tinyurl.com/2nxxaq


    Knowledge is power.
    Power corrupts.

    Study hard and be
    Eeeeviiiil......





    From: [email protected] [mailto:[email protected]]
    On Behalf Of rin1008
    Sent: Thursday, October 02, 2008 6:01
    AM
    To: [email protected]
    Subject: [CCIE SP] Vol
    I - MPLS Traffic Engineering - Explicit PE to PE Tunnels
    Lab


    Hi all,

    I'm having trouble understanding how path-option under TE tunnel works. Here
    is my case 

    - Create 2 path-option: 1 dynamic & 1 explicit

    Rack1R3#sho run int tu34  
    Building
    configuration...

    Current configuration : 321 bytes
    !
    interface
    Tunnel34
     ip unnumbered Loopback0
     tunnel destination
    150.1.4.4
     tunnel mode mpls traffic-eng
     tunnel mpls traffic-eng
    autoroute announce
     tunnel mpls traffic-eng priority 6 6
     tunnel
    mpls traffic-eng path-option 5 explicit name R3->R4
     tunnel mpls
    traffic-eng path-option 10 dynamic
     no routing dynamic
    end

    Rack1R3#sho ip explicit
    PATH R3->R4 (strict source route, path
    complete, generation 7)
        1: next-address
    150.1.13.1
        2: next-address
    150.1.12.2
        3: next-address
    150.1.25.5
        4: next-address
    150.1.45.4
        5: next-address 150.1.4.4

    - R3 uses explicit path after configuration

    Rack1R3#sho mpls tr tu tu34

    Name:
    Rack1R3_t34                        
    (Tunnel34) Destination: 150.1.4.4
      Status:
        Admin:
    up         Oper:
    up     Path: valid      
    Signalling: connected

        path option 5, type explicit
    R3->R4 (Basis for Setup, path weight 4)
        path option 10,
    type dynamic

      Config Parameters:
        Bandwidth:
    0        kbps (Global)  Priority:
    6  6   Affinity: 0x0/0xFFFF
        Metric Type: TE
    (default)
        AutoRoute:  enabled   LockDown:
    disabled  Loadshare: 0       
    bw-based
        auto-bw: disabled

      InLabel 
    :  -
      OutLabel : Serial1/2, 27
      RSVP Signalling
    Info:
           Src 150.1.3.3, Dst 150.1.4.4,
    Tun_Id 34, Tun_Instance 58
        RSVP Path
    Info:
          My Address: 150.1.3.3  

          Explicit Route: 150.1.13.1 150.1.12.1
    150.1.12.2 150.1.25.5

                         
    150.1.45.4 150.1.4.4
          Record Route: 
    NONE
          Tspec: ave rate=0 kbits, burst=1000
    bytes, peak rate=0 kbits
        RSVP Resv
    Info:
          Record Route: 
    NONE
          Fspec: ave rate=0 kbits, burst=1000
    bytes, peak rate=0 kbits
      Shortest Unconstrained Path
    Info:
        Path Weight: 3 (TE)
        Explicit
    Route: 150.1.13.1 150.1.12.1 150.1.12.2 150.1.24.4

                       
    150.1.4.4
      History:
       
    Tunnel:
          Time since created: 4 hours, 46
    minutes
          Time since path change: 16
    seconds
        Current LSP:
         
    Uptime: 16 seconds
        Prior
    LSP:
          ID: path option 10
    [57]
          Removal Trigger: path option removed

    - Shutdown interface 150.1.25.5 on R5, R3 changes to use the dynamic
    path

    Rack1R3#sho mpls tr tu tu34

    Name:
    Rack1R3_t34                        
    (Tunnel34) Destination: 150.1.4.4
      Status:
        Admin:
    up         Oper:
    up     Path: valid      
    Signalling: connected

        path option 10, type dynamic
    (Basis for Setup, path weight 3)
        path option 5, type
    explicit R3->R4

      Config Parameters:
       
    Bandwidth: 0        kbps (Global) 
    Priority: 6  6   Affinity: 0x0/0xFFFF
       
    Metric Type: TE (default)
        AutoRoute: 
    enabled   LockDown: disabled  Loadshare:
    0        bw-based
       
    auto-bw: disabled

      InLabel  :  -
      OutLabel :
    Serial1/2, 25
      RSVP Signalling
    Info:
           Src 150.1.3.3, Dst 150.1.4.4,
    Tun_Id 34, Tun_Instance 60
        RSVP Path
    Info:
          My Address: 150.1.3.3  

          Explicit Route: 150.1.13.1 150.1.12.1
    150.1.12.2 150.1.24.4

                         
    150.1.4.4
          Record Route: 
    NONE
          Tspec: ave rate=0 kbits, burst=1000
    bytes, peak rate=0 kbits
        RSVP Resv
    Info:
          Record Route: 
    NONE
          Fspec: ave rate=0 kbits, burst=1000
    bytes, peak rate=0 kbits
      Shortest Unconstrained Path
    Info:
        Path Weight: 3 (TE)
        Explicit
    Route: 150.1.13.1 150.1.12.1 150.1.12.2 150.1.24.4

                       
    150.1.4.4
      History:
       
    Tunnel:
          Time since created: 4 hours, 48
    minutes
          Time since path change: 4
    seconds
        Current LSP:
         
    Uptime: 4 seconds
          Selection:
    reoptimation
        Prior LSP:
         
    ID: path option 5 [58]
          Removal Trigger: path
    error
          Last Error: PCALC:: Can't use link
    150.1.25.5 on node 150.1.5.5

    - However, when I bring up the interface 150.1.25.5 on R5 again, R3
    do not switch back to the explicit path although its preference is lower

    My questions are:

    1. Can MPLS TE Tunnel switch back to use the explicit path if the explicit
    path is available?

    2. If not, how can we force MPLS TE to do that?

    Thanks

     

     




    Internetwork
    Expert - The Industry Leader in CCIE
    Preparation
    http://www.internetworkexpert.com

    Subscription information
    may be found
    at:
    http://www.ieoc.com/forums/ForumSubscriptions.aspx
Sign In or Register to comment.