Agile Carrier Ethernet (ACE) solution leverages Segment Routing-based transport for consolidated VPN services. In metro rings architecture, the access rings do not share their routing topologies with each other.

The SR TE On demand LSP feature provides the ability to connect Metro access rings via a static route to the destination. The static route is mapped to an explicit path and that will trigger an on demand LSP to the destination. The SR TE On demand LSP feature is used to transport the VPN services between the Metro access rings.

Inter-Metro LSPs have the following aspects:

• The source packet may not know the IP address of the destination device.

• Existing segment routing features are applicable for LSPs.

• The binding SID helps in steering the traffic in the SR-TE tunnel. In other words, ingress MPLS packet with the binding SID will be forwarded through the specific SR-TE tunnel.

As explained in the previous section, you can set up LSP as static route to create an auto tunnel by specifying an IP explicit path.

The explicit path is a combination of IP addresses (or) IP address and labels. You can also configure the static SRTE tunnel over unnumbered interfaces. There are few restrictions for unnumbered interfaces against numbered interfaces.

• You must specify the node IP address, not the next hop interface address in the ip-explicit path option.
• You must not specify adjacency SID in the explicit path option. In short, the explicit path option should contain only the node IP address (/32 mask) and prefix SID labels.

To avoid packet drop after RP switchover with SR TE, it is recommended to use the following command:

mpls traffic-eng nsr

If ISIS is configured, use the following command:

router isis
 nsf cisco
 nsf interval 0

Perform this task to configure auto tunnel static route as follows:

• Configure IP explicit path
• Associate the auto tunnel with an IP explicit path with a static route
• Enable peer-to-peer (P2P) auto tunnel service

ip explicit-path name path1
 index 1 next-label 16002
 index 2 next-label 16006
 exit
mpls traffic-eng auto-tunnel p2p
mpls traffic-eng auto-tunnel p2p config unnumbered-interface loopback0
mpls traffic-eng auto-tunnel p2p tunnel-num min 10 max 100
ip route 172.16.0.1 255.240.0.0 segment-routing mpls path name path1

The command show mpls traffic-eng service summary displays all registered TE service clients and statistics that use TE auto tunnel.

Device# show mpls traffic-eng service summary
Service Clients Summary:
  Client: BGP TE
    Client ID                 :0
    Total P2P tunnels         :1
    P2P add requests          :6
    P2P delete requests       :5
P2P add falis             :0
  P2P delete falis          :0
  P2P notify falis          :0
  P2P notify succs          :12
  P2P replays               :0
Client: ipv4static
  Client ID                 :1
  Total P2P tunnels         :1
  P2P add requests          :6
  P2P delete requests       :5
  P2P add falis             :0
  P2P delete falis          :0
  P2P notify falis          :0
  P2P notify succs          :85
  P2P replays               :0

The command show mpls traffic-eng auto-tunnel p2p displays the peer-to-peer (P2P) auto tunnel configuration and operation status.

The command show mpls traffic-eng tunnel summary displays the status of P2P auto tunnel.

Device# show mpls traffic-eng auto-tunnel p2p
State: Enabled
  p2p auto-tunnels: 2 (up: 2, down: 0)
  Default Tunnel ID Range: 62336 - 64335
  Config:
unnumbered-interface: Loopback0 Tunnel ID range: 1000 – 2000

The command show mpls traffic-eng tunnel summary displays the status of P2P auto tunnel.

Device# show mpls traffic-eng tunnel summary
Signalling Summary:
    LSP Tunnels Process:
    Passive LSP Listener:
    RSVP Process:
    Forwarding:
    auto-tunnel:
running
running
running
enabled
p2p    Enabled  (1), id-range:1000-2000
Periodic reoptimization:
Periodic FRR Promotion:
Periodic auto-bw collection:
SR tunnel max label push:
P2P:
every 3600 seconds, next in 1265 seconds
Not Running
every 300 seconds, next in 66 seconds
13 labels
      Head: 11 interfaces,   5234 active signalling attempts, 1 established
            5440 activations,  206 deactivations
            1821 failed activations
            0 SSO recovery attempts, 0 SSO recovered
      Midpoints: 0, Tails: 0
    P2MP:
      Head: 0 interfaces,   0 active signalling attempts, 0 established
            0 sub-LSP activations,  0 sub-LSP deactivations
            0 LSP successful activations,  0 LSP deactivations
            0 SSO recovery attempts, LSP recovered: 0 full, 0 partial, 0 fail
      Midpoints: 0, Tails: 0
Bidirectional Tunnel Summary:
    Tunnel Head: 0 total, 0 connected, 0 associated, 0 co-routed
LSPs Head:
LSPs Mid:
LSPs Tail:
0 established, 0 proceeding, 0 associated, 0 standby
0 established, 0 proceeding, 0 associated, 0 standby
0 established, 0 proceeding, 0 associated, 0 standby
AutoTunnel P2P Summary:
    ipv4static:
        Tunnels: 1 created, 1 up, 0 down
    Total:
        Tunnels: 1 created, 1 up, 0 down

The command show ip explicit-path displays the configured IP explicit paths.

Device# show ip explicit-path
PATH path1 (strict source route, path complete, generation 5)
    1: next-label 16055
    2: next-label 16070
    3: next-label 16010
PATH path2 (strict source route, path complete, generation 9)
    1: next-label 16070
    2: next-label 16010
Device# show running-config | i ip route
ip route  10.10.10.10 255.255.255.255 segment-routing mpls path name path1 verbatim
ip route  11.11.11.1 255.255.255.255 segment-routing mpls path name path2 verbatim
ip route  11.11.11.2 255.255.255.255 segment-routing mpls path name path2 verbatim

The command show mpls traffic-eng tunnel auto-tunnel detail only displays TE service auto tunnel.

Device# show mpls traffic-eng tunnel auto-tunnel detail
P2P TUNNELS/LSPs:
 
Name: R1-RSP2_t4000                       (Tunnel4000) Destination: 0.0.0.0 Ifhandle: 0x23 (auto-tunnel for ipv4static)
  Status:
    Admin: up         Oper: up     Path: valid       Signalling: connected
    path option 1, (SEGMENT-ROUTING) type explicit (verbatim) path1 (Basis for Setup)
 
  Config Parameters:
    Bandwidth: 0        kbps (Global)  Priority: 7  7   Affinity: 0x0/0xFFFF
    Metric Type: TE (default)
    Path Selection:
     Protection: any (default)
    Path-selection Tiebreaker:
      Global: not set   Tunnel Specific: not set   Effective: min-fill (default)
    Hop Limit: disabled [ignore: Verbatim Path Option]
    Cost Limit: disabled
    Path-invalidation timeout: 10000 msec (default), Action: Tear
    AutoRoute: disabled LockDown: disabled Loadshare: 0 [0] bw-based
    auto-bw: disabled
    Fault-OAM: disabled, Wrap-Protection: disabled, Wrap-Capable: No
  Active Path Option Parameters:
    State: explicit path option 1 is active
    BandwidthOverride: disabled  LockDown: disabled  Verbatim: enabled
 
  History:
    Tunnel:
      Time since created: 7 days, 22 hours, 48 minutes
      Time since path change: 7 days, 22 hours, 47 minutes
      Number of LSP IDs (Tun_Instances) used: 9
    Current LSP: [ID: 9]
      Uptime: 7 days, 22 hours, 47 minutes
  Tun_Instance: 9
  Segment-Routing Path Info (IGP information is not used)
    Segment0[First Hop]: 0.0.0.0, Label: 16055
    Segment1[ - ]: Label: 16070
    Segment2[ - ]: Label: 16010

The command show mpls traffic-eng tunnel brief displays auto tunnel information.

Device# show mpls traffic-eng tunnel brief
Signalling Summary:
    LSP Tunnels Process:	running
    Passive LSP Listener:	running
    RSVP Process:		running
    Forwarding:			enabled
    auto-tunnel:
	p2p    Enabled  (2), id-range:1000-2000
    Periodic reoptimization:		every 3600 seconds, next in 406 seconds
    Periodic FRR Promotion:		Not Running
    Periodic auto-bw collection:	every 300 seconds, next in 107 seconds
    SR tunnel max label push:		13 labels
P2P TUNNELS/LSPs:
TUNNEL NAME				DESTINATION			UP IF			DOWN IF			STATE/PROT
R1_t1					66.66.66.66			-			-			up/down
R1_t2					66.66.66.66			-			-			up/down	
R1_t3					66.66.66.66			-			-			up/down
R1_t10					66.66.66.66			-			-			up/down
SBFD tunnel					33.33.33.33			-			-			up/down
SBFD Session configured: 1		SBFD sessions UP: 1