Configuring a Mesh of SR-TE Auto-LSPs

The following shows the detailed configuration for the creation of a mesh of SR-TE auto-LSPs. The network uses IS-IS with the backbone area being in Level 2 and the leaf areas being in Level 1.

The NSP is used for network discovery only and the NRC-P learns the network topology using BGP-LS.

Figure 1 shows the view of the multi-level IS-IS topology in the NSP GUI. The backbone L2 area is highlighted in green.

Figure 1. Multi-level IS-IS Topology in the NSP GUI

The mesh of SR-TE auto-LSPs is created in the backbone area and originates on an ABR node with address 192.168.48.199 (Phoenix 199). The LSP template uses a default path that includes an anycast SID prefix corresponding to a transit routers 192.168.48.184 (Dallas 184) and 192.168.48.185 (Houston 185).

The following is the configuration of transit router Dallas 184, which shows the creation of a loopback interface with the anycast prefix and the assignment of a SID to it. The same configuration must be performed on the transit router Houston 185. See lines marked with an asterisk (*).

*A:Dallas 184>config>router# info
---------------------------------------------------
echo "IP Configuration"
#--------------------------------------------------
        if-attribute
            admin-group "olive" value 20
            admin-group "top" value 10
            srlg-group "top" value 10
        exit
        interface "anycast-sid"                                                    *
            address 192.168.48.99/32                                               *
            loopback                                                               *
            no shutdown                                                            *
        exit
        interface "system"
            address 192.168.48.184/32
            no shutdown
        exit
        interface "toJun164"
            address 10.19.2.184/24
            port 1/1/4:10
            no shutdown
        exit
        interface "toSim185"
            address 10.0.3.184/24
            port 1/1/2
            no shutdown
        exit
        interface "toSim198"
            address 10.0.2.184/24
            port 1/1/3
            if-attribute
                admin-group "olive"
            exit
            no shutdown
        exit
        interface "toSim199"
            address 10.0.13.184/24
            port 1/1/5
            no shutdown
        exit
        interface "toSim221"
            address 10.0.4.184/24
            port 1/1/1
            no shutdown
        exit
        interface "toSim223"
            address 10.0.14.184/24
            port 1/1/6
            no shutdown
        exit
#--------------------------------------------------

*A:Dallas 184>config>router>isis# info
----------------------------------------------
            level-capability level-2
            area-id 49.0000
            database-export identifier 10 bgp-ls-identifier 10
            traffic-engineering
            advertise-router-capability area
            level 2
                wide-metrics-only
            exit
            interface "system"
                ipv4-node-sid index 384
                no shutdown
            exit
            interface "toSim198"
                interface-type point-to-point
                no shutdown
            exit
            interface "toSim185"
                interface-type point-to-point
                no shutdown
            exit
            interface "toSim221"
                interface-type point-to-point
                no shutdown
            exit
            interface "toSim199"
                interface-type point-to-point
                level 2
                    metric 100
                exit
                no shutdown
            exit
            interface "toSim223"
                interface-type point-to-point
                level 2
                    metric 100
                exit
                no shutdown
            exit
            interface "anycast-sid"                                                *
                ipv4-node-sid index 99                                             *
                no shutdown                                                        *
            exit
            segment-routing
                prefix-sid-range global
                no shutdown
            exit
            no shutdown
----------------------------------------------

In the ingress LER Phoenix 199 router, the anycast SID is learned from both transit routers, but is currently resolved in IS-IS to transit router Houston 185. See lines marked with an asterisk (*).

*A:Phoenix 199# show router isis prefix-sids
===============================================================================
Rtr Base ISIS Instance 0 Prefix/SID Table
===============================================================================
Prefix                            SID        Lvl/Typ    SRMS   AdvRtr
                                                         MT     Flags
-------------------------------------------------------------------------------
192.168.48.194/32                  399        1/Int.      N     Reno 194
                                                            0       NnP
192.168.48.194/32                  399        2/Int.      N     Salt Lake 198
                                                            0       RNnP
192.168.48.194/32                  399        2/Int.      N     Phoenix 199
                                                            0       RNnP
192.168.48.99/32                   99         2/Int.      N     Dallas 184         *
                                                            0       NnP            *
192.168.48.99/32                   99         2/Int.      N     Houston 185        *
                                                            0       NnP            *
192.168.48.184/32                  384        2/Int.      N     Dallas 184
                                                            0       NnP
192.168.48.185/32                  385        2/Int.      N     Houston 185
                                                            0       NnP
192.168.48.190/32                  390        2/Int.      N     Chicago 221
                                                            0       RNnP
192.168.48.190/32                  390        2/Int.      N     St Louis 223
                                                            0       RNnP
192.168.48.194/32                  394        1/Int.      N     Reno 194
                                                            0       NnP
192.168.48.194/32                  394        2/Int.      N     Salt Lake 198
                                                            0       RNnP
192.168.48.194/32                  394        2/Int.      N     Phoenix 199
                                                            0       RNnP
192.168.48.198/32                  398        1/Int.      N     Salt Lake 198
                                                            0       NnP
192.168.48.198/32                  398        2/Int.      N     Salt Lake 198
                                                            0       NnP
192.168.48.198/32                  398        2/Int.      N     Phoenix 199
                                                            0       RNnP
192.168.48.199/32                  399        2/Int.      N     Salt Lake 198
                                                            0       RNnP
192.168.48.199/32                  399        1/Int.      N     Phoenix 199
                                                            0       NnP
192.168.48.199/32                  399        2/Int.      N     Phoenix 199
                                                            0       NnP
192.168.48.219/32                  319        2/Int.      N     Salt Lake 198
                                                            0       RNnP
192.168.48.219/32                  319        2/Int.      N     Phoenix 199
                                                            0       RNnP
192.168.48.219/32                  319        1/Int.      N     Las Vegas 219
                                                            0       NnP
192.168.48.221/32                  321        2/Int.      N     Chicago 221
                                                            0       NnP
192.168.48.221/32                  321        2/Int.      N     St Louis 223
                                                            0       RNnP
192.168.48.223/32                  323        2/Int.      N     Chicago 221
                                                            0       RNnP
192.168.48.223/32                  323        2/Int.      N     St Louis 223
                                                            0       NnP
192.168.48.224/32                  324        2/Int.      N     Chicago 221
                                                            0       RNnP
192.168.48.224/32                  324        2/Int.      N     St Louis 223
                                                            0       RNnP
192.168.48.226/32                  326        2/Int.      N     PCE Server 226
                                                            0       NnP
3ffe::a14:194/128                  294        1/Int.      N     Reno 194
                                                            0       NnP
3ffe::a14:194/128                  294        2/Int.      N     Phoenix 199
                                                            0       RNnP
3ffe::a14:199/128                  299        1/Int.      N     Phoenix 199
                                                            0       NnP
3ffe::a14:199/128                  299        2/Int.      N     Phoenix 199
                                                            0       NnP
-------------------------------------------------------------------------------
No. of Prefix/SIDs: 32 (15 unique)
-------------------------------------------------------------------------------
SRMS : Y/N  = prefix SID advertised by SR Mapping Server (Y) or not (N)
       S    = SRMS prefix SID is selected to be programmed
Flags: R    = Re-advertisement
       N    = Node-SID
       nP   = no penultimate hop POP
       E    = Explicit-Null
       V    = Prefix-SID carries a value
       L    = value/index has local significance
===============================================================================

*A:Phoenix 199# tools dump router segment-routing tunnel
====================================================================================
Legend: (B) - Backup Next-hop for Fast Re-Route                                 
        (D) - Duplicate                                                         
====================================================================================
-----------------------------------------------------------------------------------+
 Prefix                                                                            |
 Sid-Type        Fwd-Type       In-Label  Prot-Inst                                |
                 Next Hop(s)                      Out-Label(s) Interface/Tunnel-ID |
-----------------------------------------------------------------------------------+
 192.168.48.99                                                                     *
 Node            Orig/Transit   200099    ISIS-0                                   *
                 10.0.5.185                       200099      toSim185             *
 3ffe::a14:194
 Node            Orig/Transit   200294    ISIS-0
                 fe80::62c2:ffff:fe00:0           200294      toSim194
 3ffe::a14:199
 Node            Terminating    200299    ISIS-0
 192.168.48.219
 Node            Orig/Transit   200319    ISIS-0
                 10.202.5.194                     200319      toSim194
 192.168.48.221
 Node            Orig/Transit   200321    ISIS-0
                 10.0.5.185                       200321      toSim185
 192.168.48.223
 Node            Orig/Transit   200323    ISIS-0
                 10.0.5.185                       200323      toSim185
 192.168.48.224
 Node            Orig/Transit   200324    ISIS-0
                 10.0.5.185                       200324      toSim185
 192.168.48.226
 Node            Orig/Transit   200326    ISIS-0
                 10.0.1.2                         100326      toSim226PCEServer
 192.168.48.184
 Node            Orig/Transit   200384    ISIS-0
                 10.0.5.185                       200384      toSim185
 192.168.48.185
 Node            Orig/Transit   200385    ISIS-0
                 10.0.5.185                       200385      toSim185
 192.168.48.190
 Node            Orig/Transit   200390    ISIS-0
                 10.0.5.185                       200390      toSim185
 192.168.48.194
 Node            Orig/Transit   200394    ISIS-0
                 10.202.5.194                     200394      toSim194
 192.168.48.198
 Node            Orig/Transit   200398    ISIS-0
                 10.0.9.198                       100398      toSim198
 192.168.48.199
 Node            Terminating    200399    ISIS-0
 10.0.9.198
 Adjacency       Transit        262122    ISIS-0
                 10.0.9.198                       3           toSim198
 10.202.1.219
 Adjacency       Transit        262124    ISIS-0
                 10.202.1.219                     3           toSim219
 10.0.5.185
 Adjacency       Transit        262133    ISIS-0
                 10.0.5.185                       3           toSim185
 fe80::62c2:ffff:fe00:0
 Adjacency       Transit        262134    ISIS-0
                 fe80::62c2:ffff:fe00:0           3           toSim194
 10.0.1.2
 Adjacency       Transit        262137    ISIS-0
                 10.0.1.2                         3           toSim226PCEServer
 10.0.13.184
 Adjacency       Transit        262138    ISIS-0
                 10.0.13.184                      3           toSim184
 10.0.2.2
 Adjacency       Transit        262139    ISIS-0
                 10.0.2.2                         3           toSim226PCEserver202
 10.202.5.194
 Adjacency       Transit        262141    ISIS-0
                 10.202.5.194                     3           toSim194
------------------------------------------------------------------------------------
No. of Entries: 22
------------------------------------------------------------------------------------

Next, a policy must be configured to add the list of prefixes to which the ingress LER Phoenix 199 must auto-create SR-TE LSPs.

*A:Phoenix 199>config>router>policy-options# info
----------------------------------------------
            prefix-list "sr-te-level2"
                prefix 192.168.48.198/32 exact
                prefix 192.168.48.221/32 exact
                prefix 192.168.48.223/32 exact
            exit
            policy-statement "sr-te-auto-lsp"
                entry 10
                    from
                        prefix-list "sr-te-level2"
                    exit
                    action accept
                    exit
                exit
                default-action drop
                exit
            exit
----------------------------------------------

Then, an LSP template of type mesh-p2p-srte must be configured, which uses a path with a loose-hop corresponding to anycast-SID prefix of the transit routers. The LSP template is then bound to the policy containing the prefix list. See lines marked with an asterisk (*).

*A:Phoenix 199>config>router>mpls# info
----------------------------------------------
            cspf-on-loose-hop
            interface "system"
                no shutdown
            exit
            interface "toESS195"
                no shutdown
            exit
            interface "toSim184"
                no shutdown
            exit
            interface "toSim185"
                admin-group "bottom"
                srlg-group "bottom"
                no shutdown
            exit
            interface "toSim194"
                admin-group "bottom"
                srlg-group "bottom"
                no shutdown
            exit
            interface "toSim198"
                no shutdown
            exit
            interface "toSim219"
                no shutdown
            exit
            path "loose-anycast-sid"                                               *
                hop 1 192.168.48.99 loose                                          *
                no shutdown                                                        *
            exit                                                                   *
            lsp-template "sr-te-level2-mesh" mesh-p2p-srte                         *
                default-path "loose-anycast-sid"                                   *
                max-sr-labels 8 additional-frr-labels 2                            *
                pce-report enable                                                  *
                no shutdown                                                        *
            exit                                                                   *
            auto-lsp lsp-template "sr-te-level2-mesh" policy "sr-te-auto-lsp"      *
            no shutdown                                                            *
----------------------------------------------

One SR-TE LSP should be automatically created to each destination matching the prefix in the policy as soon as the router with the router ID matching the address of the prefix appears in the TE database.

The following shows the three SR-TE auto-LSPs created. See lines marked with an asterisk (*).

*A:Phoenix 199# show router mpls sr-te-lsp
===============================================================================
MPLS SR-TE LSPs (Originating)
===============================================================================
LSP Name                           To               Tun     Protect   Adm  Opr
                                                    Id      Path
-------------------------------------------------------------------------------
Phoenix-SL-1                       192.168.48.223    1       N/A       Up   Up
Phoenix-SL-2-Profile               192.168.48.223    2       N/A       Up   Up
Phoenix-SL-3-Profile               192.168.48.223    3       N/A       Up   Up
Phoenix-SL-4-Profile               192.168.48.223    4       N/A       Up   Up
Phoenix-SL-1-Profile               192.168.48.223    5       N/A       Up   Up
Phoenix-SL-2                       192.168.48.223    6       N/A       Up   Up
Phoenix-SL-3                       192.168.48.223    7       N/A       Up   Up
Phoenix-SL-4                       192.168.48.223    8       N/A       Up   Up
sr-te-level2-mesh-192.168.48.198-  192.168.48.198    61442   N/A       Up   Up     *
716803                                                                             *
sr-te-level2-mesh-192.168.48.221-  192.168.48.221    61443   N/A       Up   Up     *
716804                                                                             *
sr-te-level2-mesh-192.168.48.223-  192.168.48.223    61444   N/A       Up   Up     *
716805                                                                             *
-------------------------------------------------------------------------------
LSPs : 17
===============================================================================

The auto-generated name uses the syntax convention ‟TemplateName-DestIpv4Address-TunnelId”, as explained in Automatic Creation of an SR-TE Mesh LSP. The tunnel ID used in the name is the TTM tunnel ID, not the MPLS LSP tunnel ID. See lines marked with an asterisk (*).

*A:Phoenix 199# show router mpls sr-te-lsp "sr-te-level2-mesh-192.168.48.223-
716805" detail
===============================================================================
MPLS SR-TE LSPs (Originating) (Detail)
===============================================================================
-------------------------------------------------------------------------------
Type : Originating
-------------------------------------------------------------------------------
LSP Name        : sr-te-level2-mesh-192.168.48.223-716805
LSP Type        : MeshP2PSrTe               LSP Tunnel ID        : 61444           *
LSP Index       : 126979                    TTM Tunnel Id        : 716805          *
From            : 192.168.48.199            To                   : 192.168.48.2*
Adm State       : Up                        Oper State           : Up
LSP Up Time     : 0d 00:02:12               LSP Down Time        : 0d 00:00:00
Transitions     : 3                         Path Changes         : 3
Retry Limit     : 0                         Retry Timer          : 30 sec
CSPF            : Enabled
Metric          : N/A                       Use TE metric        : Disabled
Include Grps    :                           Exclude Grps         :
None                                           None
VprnAutoBind    : Enabled
IGP Shortcut    : Enabled                   BGP Shortcut         : Enabled
IGP LFA         : Disabled                  IGP Rel Metric       : Disabled
BGPTransTun     : Enabled
Oper Metric     : 16777215
PCE Report      : Enabled
PCE Compute     : Disabled                  PCE Control          : Disabled
Max SR Labels   : 8                         Additional FRR Labels: 2
Path Profile    :
None
Primary(a)      : loose-anycast-sid         Up Time              : 0d 00:02:12
Bandwidth       : 0 Mbps
===============================================================================

These SR-TE auto-LSPs are also added into the tunnel table to be used by services and shortcut applications. See lines marked with an asterisk (*).

*A:Phoenix 199# show router tunnel-table
===============================================================================
IPv4 Tunnel Table (Router: Base)
===============================================================================
Destination       Owner     Encap TunnelId  Pref     Nexthop        Metric
-------------------------------------------------------------------------------
10.0.5.185/32     isis (0)  MPLS  524370    11       10.0.5.185     0
10.0.9.198/32     isis (0)  MPLS  524368    11       10.0.9.198     0
10.0.13.184/32    isis (0)  MPLS  524340    11       10.0.13.184    0
10.202.1.219/32   isis (0)  MPLS  524333    11       10.202.1.219   0
10.202.5.194/32   isis (0)  MPLS  524355    11       10.202.5.194   0
10.0.1.2/32       isis (0)  MPLS  524364    11       11.0.1.2       0
10.0.2.2/32       isis (0)  MPLS  524363    11       11.0.2.2       0
192.168.48.99/32  isis (0)  MPLS  524294    11       10.0.5.185     10
192.168.48.184/32 ldp       MPLS  65605     9        10.0.5.185     20
192.168.48.184/32 isis (0)  MPLS  524341    11       10.0.5.185     20
192.168.48.185/32 ldp       MPLS  65602     9        10.0.5.185     10
192.168.48.185/32 isis (0)  MPLS  524371    11       10.0.5.185     10
192.168.48.190/32 ldp       MPLS  65606     9        10.0.5.185     40
192.168.48.190/32 isis (0)  MPLS  524362    11       10.0.5.185     40
192.168.48.194/32 ldp       MPLS  65577     9        10.202.5.194   10
192.168.48.194/32 isis (0)  MPLS  524331    11       10.202.5.194   10
192.168.48.198/32 sr-te     MPLS  716803    8        192.168.48.99  16777215      *
192.168.48.198/32 ldp       MPLS  65601     9        10.0.9.198     10
192.168.48.198/32 isis (0)  MPLS  524369    11       10.0.9.198     10
192.168.48.219/32 ldp       MPLS  65579     9        10.202.5.194   20
192.168.48.219/32 isis (0)  MPLS  524334    11       10.202.5.194   20
192.168.48.221/32 sr-te     MPLS  716804    8        192.168.48.99  16777215      *
192.168.48.221/32 ldp       MPLS  65607     9        10.0.5.185     30
192.168.48.221/32 isis (0)  MPLS  524358    11       10.0.5.185     30
192.168.48.223/32 sr-te     MPLS  655362    8        10.0.13.184    200
192.168.48.223/32 sr-te     MPLS  655363    8        10.0.13.184    200
192.168.48.223/32 sr-te     MPLS  655364    8        10.0.5.185     40
192.168.48.223/32 sr-te     MPLS  655365    8        10.0.13.184    120
192.168.48.223/32 sr-te     MPLS  655366    8        10.0.5.185     120
192.168.48.223/32 sr-te     MPLS  655367    8        10.0.13.184    120
192.168.48.223/32 sr-te     MPLS  655368    8        10.0.13.184    200
192.168.48.223/32 sr-te     MPLS  655369    8        10.0.5.185     40
192.168.48.223/32 sr-te     MPLS  716805    8        192.168.48.99  16777215      *
192.168.48.223/32 ldp       MPLS  65603     9        10.0.5.185     20
192.168.48.223/32 isis (0)  MPLS  524306    11       10.0.5.185     20
192.168.48.224/32 ldp       MPLS  65604     9        10.0.5.185     30
192.168.48.224/32 isis (0)  MPLS  524361    11       10.0.5.185     30
192.168.48.226/32 isis (0)  MPLS  524365    11       11.0.1.2       65534
-------------------------------------------------------------------------------
Flags: B = BGP backup route available
       E = inactive best-external BGP route
===============================================================================

The details of the path of one of the SR-TE auto-LSPs now show the ERO transiting through the anycast SID of router Houston 185. See lines marked with an asterisk (*).

*A:Phoenix 199# show router mpls sr-te-lsp "sr-te-level2-mesh-192.168.48.223-
716805" path detail
===============================================================================
MPLS SR-TE LSP sr-te-level2-mesh-192.168.48.223-716805 Path  (Detail)
===============================================================================
Legend :
    S      - Strict                      L      - Loose
    A-SID  - Adjacency SID               N-SID  - Node SID
    +      - Inherited
===============================================================================
-------------------------------------------------------------------------------
SR-TE LSP sr-te-level2-mesh-192.168.48.223-716805 Path loose-anycast-sid
-------------------------------------------------------------------------------
LSP Name         : sr-te-level2-mesh-192.168.48.223-716805
Path LSP ID      : 20480
From             : 192.168.48.199       To                   : 192.168.48.223
Admin State      : Up                   Oper State           : Up
Path Name        : loose-anycast-sid    Path Type            : Primary
Path Admin       : Up                   Path Oper            : Up
Path Up Time     : 0d 02:30:28          Path Down Time       : 0d 00:00:00
Retry Limit      : 0                    Retry Timer          : 30 sec
Retry Attempt    : 1                    Next Retry In        : 0 sec
CSPF             : Enabled              Oper CSPF            : Enabled
Bandwidth        : No Reservation       Oper Bandwidth       : 0 Mbps
Hop Limit        : 255                  Oper HopLimit        : 255
Setup Priority   : 7                    Oper Setup Priority  : 7
Hold Priority    : 0                    Oper Hold Priority   : 0
Inter-area       : N/A
PCE Updt ID      : 0                    PCE Updt State       : None
PCE Upd Fail Code: noError
PCE Report       : Enabled              Oper PCE Report      : Disabled
PCE Control      : Disabled             Oper PCE Control     : Disabled
PCE Compute      : Disabled
Include Groups   :                      Oper Include Groups  :
None                                           None
Exclude Groups   :                      Oper Exclude Groups  :
None                                           None
IGP/TE Metric    : 16777215             Oper Metric          : 16777215
Oper MTU         : 1492                 Path Trans           : 1
Failure Code     : noError
Failure Node     : n/a
Explicit Hops    :
    192.168.48.99(L)
Actual Hops      :
    192.168.48.99 (192.168.48.185)(N-SID)          Record Label        : 200099    *
 -> 192.168.48.223 (192.168.48.223)(N-SID)         Record Label        : 200323    *
===============================================================================