SR-MPLS –  Static non-colored LSP 

1. Intro

The segment routing architecture enables the ingress devices in a core network to steer traffic through explicit paths. You can configure these paths using segment lists to define the paths that the incoming traffic should take.

SR is a control-plane architecture that enables an ingress devices in a core network to steer traffic through a specific set of nodes and links in the network without relying on the intermediate nodes in the network to determine the actual path it should take. You can configure these paths using segment lists to define the paths that the incoming traffic should take.

Segment routing LSPs can either be dynamic or static in nature.

• Dynamic SR LSPs – When a segment routing LSP is created either by an external controller and downloaded to an ingress device through Path Computation Element Protocol (PCEP) extensions, or through BGP segment routing extensions. (not covered by this post), or using Distributed CSPF (D-CSPF).
• Static SR LSPs – When a segment routing LSP is created on the ingress device through local configuration, the LSP is statically provisioned. Can be further classified as:
  • colored (will be covered in a different post)
  • non-colored LSPs 

The static non-colored segment routing LSP has a unique name and a destination IP address. An ingress route to the destination is installed in the inet.3 routing table with a default preference of 8 and a metric of 1. 

You can configure segment routing tunnel by configuring the source-routing-path statement. The SR tunnel has a destination address and one or more primary paths and optionally secondary paths that refer to the segment list.

The segment list is a set of explicit SR paths are configured on the ingress router by configuring the segment-list statement. Each segment list consists of a sequence of hops.

For non-colored static segment routing tunnel, the first hop of the segment list specifies an immediate next hop IP address and the second to Nth hop specifies the segment identifies (SID) labels corresponding to the link or node which the path traverses.

2. Configuration

Because we are continuing the previous post by configuring a static non-colored LSP, we are using the same topology:

A quick refresh, the SR-MPLS config was already applied on all routers:

set protocols isis source-packet-routing srgb start-label 800000
set protocols isis source-packet-routing srgb index-range 10000
set protocols isis source-packet-routing node-segment ipv4-index 1001
set protocols isis source-packet-routing node-segment ipv6-index 5001

To create our 1st static non-colored LSP, the destination will be router R8:

### Configure the segment list: 

set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 ip-address 17.1.3.3
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 label 801006
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 label 801007
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label 801008

### Then configure the LSP: 

set protocols source-packet-routing source-routing-path R1-TO-R8 to 17.0.0.8
set protocols source-packet-routing source-routing-path R1-TO-R8 primary R1-TO-R8-primary 

### We must also configure 'maximum labels' for family mpls. 
### If we won't do this, then the next-hop will be unusable. 

set interfaces ge-0/0/1 unit 0 family mpls maximum-labels 16
set interfaces ge-0/0/2 unit 0 family mpls maximum-labels 16

Now, we can do multiple checks to verify the status of the newly created LSP:

### If we check the Spring TE Overview, our LSP is UP: 

root@R1# run show spring-traffic-engineering overview 
Overview of SPRING-TE:
  Route preference: 8
  Number of LSPs: 1 (Up: 1, Down: 0)
  Number of LSPs with ldp-tunneling config: 0
  External controllers:
    <Not configured>

### The LSP is UP: 

root@R1# run show spring-traffic-engineering lsp 
To              State     LSPname
17.0.0.8        Up        R1-TO-R8

### The detailed view: 

root@R1# run show spring-traffic-engineering lsp detail 
Name: R1-TO-R8
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 17.0.0.8
  Te-group-id: 0
  State: Up
    Path: R1-TO-R8-primary
    Path Status: NA
    Outgoing interface: ge-0/0/2.0
    Auto-translate status: Disabled Auto-translate result: N/A
    Compute Status:Disabled , Compute Result:N/A , Compute-Profile Name:N/A
    BFD status: N/A BFD name: N/A
    BFD remote-discriminator: N/A
    Segment ID : 128 
    ERO Valid: true
      SR-ERO hop count: 4
        Hop 1 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.1.3.3
          SID type: None
        Hop 2 (Strict): 
          NAI: None
          SID type: 20-bit label, Value: 801006
        Hop 3 (Strict): 
          NAI: None
          SID type: 20-bit label, Value: 801007
        Hop 4 (Strict): 
          NAI: None
          SID type: 20-bit label, Value: 801008

Total displayed LSPs: 1 (Up: 1, Down: 0)

### The destination was added to the inet.3 table. 
### Notice that that the SPRING-TE has a better preference.
### Also, notice the label stack that is pushed to the packets: 

root@R1# run show route table inet.3 

inet.3: 7 destinations, 8 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

17.0.0.2/32        *[L-ISIS/14] 02:27:05, metric 10
                    >  to 17.1.2.2 via ge-0/0/1.0
17.0.0.3/32        *[L-ISIS/14] 02:27:05, metric 10
                    >  to 17.1.3.3 via ge-0/0/2.0
17.0.0.4/32        *[L-ISIS/14] 02:27:05, metric 20
                    >  to 17.1.2.2 via ge-0/0/1.0, Push 801004
                       to 17.1.3.3 via ge-0/0/2.0, Push 801004
17.0.0.5/32        *[L-ISIS/14] 02:27:05, metric 30
                    >  to 17.1.2.2 via ge-0/0/1.0, Push 801005
                       to 17.1.3.3 via ge-0/0/2.0, Push 801005
17.0.0.6/32        *[L-ISIS/14] 02:27:05, metric 20
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 801006
17.0.0.7/32        *[L-ISIS/14] 02:27:05, metric 30
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 801007
17.0.0.8/32        *[SPRING-TE/8] 00:12:19, metric 1, metric2 30
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 801008, Push 801007, Push 801006(top)
                    [L-ISIS/14] 02:27:05, metric 30
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 801008

### VRF Ping works to R8: 

root@R1# run ping 192.168.8.1 routing-instance Cust-A    
PING 192.168.8.1 (192.168.8.1): 56 data bytes
64 bytes from 192.168.8.1: icmp_seq=0 ttl=62 time=5.956 ms
64 bytes from 192.168.8.1: icmp_seq=1 ttl=62 time=5.356 ms
^C
--- 192.168.8.1 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 5.356/5.656/5.956/0.300 ms

### With a tcpdump capture we can see the label stack and how each router pops one label and sends the packet further: 

### TCP Dump on R1-R3 link: 

12:44:35.642603 MPLS (label 801006, exp 0, ttl 64) (label 801007, exp 0, ttl 64) (label 801008, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 65082, seq 368, length 64

### TCP Dump on R3-R6 link: 

12:44:23.338066 MPLS (label 801007, exp 0, ttl 63) (label 801008, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 65082, seq 355, length 64

### TCP Dump on R6-R7 link:

12:44:57.507850 MPLS (label 801008, exp 0, ttl 62) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 65082, seq 389, length 64

### There are multiple valid ways to configure the LSP (the following tcpdump captures are from R1-R3 link).
### Using only Node SIDs: 

set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 label 801003
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 label 801006
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 label 801007
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label 801008

14:37:20.087522 MPLS (label 801006, exp 0, ttl 64) (label 801007, exp 0, ttl 64) (label 801008, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 59696, seq 10, length 64

### Only Adjacency SIDs:  

set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 label 23
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 label 18
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 label 20
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label 19

14:51:31.852305 MPLS (label 18, exp 0, ttl 64) (label 20, exp 0, ttl 64) (label 19, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 59696, seq 857, length 64

### Or a combination: 

set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 label 801003
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 label 18
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 label 80100
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label 19

14:58:09.871138 MPLS (label 18, exp 0, ttl 64) (label 80100, exp 0, ttl 64) (label 19, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 59696, seq 1253, length 64

### Notice that HOP1 label is used to identify the next hop, but it will not be sent on the wire. 
### R3 needs the HOP-2 label, so that will be our top label on the wire: 

17.0.0.8/32        *[SPRING-TE/8] 00:02:38, metric 1, metric2 30
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 19, Push 80100, Push 18(top)

### Note: Last label (16) is the VPN label. 

### Note2: If planning to use Adj SID labels, remember that these are dynamically allocated and not set in stone.
### The Adj SIDs might change. It is probably a good idea to statically define them: 

set protocols isis interface ge-0/0/1.0 level 2 ipv4-adjacency-segment unprotected index 1234 

### Note3: 
### Because we just seen an example using node SID labels, we should also note that we can define the segment list with only one node label.
### All routers on path will SWAP 801008 with 801008 and at the it will POP (PHP); this will take shortest path
### Probably this is not the static path you want to configure, but find one example below:  

set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label 801008

3. auto-translate

We will use interface IPs for this 1st example:

### Reconfigure the segment list so that it contains only IP Lookups: 

set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 ip-address 17.1.3.3
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 ip-address 17.3.6.6
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 ip-address 17.6.7.7
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 ip-address 17.7.8.8

### JunOS will not even let you commit: 

root@R1# commit 
[edit protocols source-packet-routing]
  'segment-list R1-TO-R8-primary'
    segment-list R1-TO-R8-primary has an invalid unknown type in the 2nd hop
error: configuration check-out failed

### We need to add the auto-translate option: 

set protocols source-packet-routing segment-list R1-TO-R8-primary auto-translate
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 ip-address 17.1.3.3
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 ip-address 17.3.6.6
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 ip-address 17.6.7.7
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 ip-address 17.7.8.8

### Still not working, we need to activate the TED: 

root@R1# run show spring-traffic-engineering lsp detail 
Name: R1-TO-R8
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 17.0.0.8
  Te-group-id: 0
  State: Down
    Path: R1-TO-R8-primary
    Path Status: NA
    Outgoing interface: NA
    Auto-translate status: Enabled Auto-translate result: TED is empty
    Compute Status:Disabled , Compute Result:N/A , Compute-Profile Name:N/A
    BFD status: N/A BFD name: N/A
    BFD remote-discriminator: N/A
    Segment ID : 128 
    ERO Valid: true
      SR-ERO hop count: 4
        Hop 1 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.1.3.3
          SID type: None
        Hop 2 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.3.6.6
          SID type: None
        Hop 3 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.6.7.7
          SID type: None
        Hop 4 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.7.8.8
          SID type: None

### To activate the TED database: 

set protocols isis traffic-engineering l3-unicast-topology

### Now the LSP is UP and we can see how the IPs were translated to Adjacency SIDs:

root@R1# run show spring-traffic-engineering lsp detail 
Name: R1-TO-R8
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 17.0.0.8
  Te-group-id: 0
  State: Up
    Path: R1-TO-R8-primary
    Path Status: NA
    Outgoing interface: ge-0/0/2.0
    Auto-translate status: Enabled Auto-translate result: Success
    Compute Status:Disabled , Compute Result:N/A , Compute-Profile Name:N/A
    BFD status: N/A BFD name: N/A
    BFD remote-discriminator: N/A
    Segment ID : 128 
    ERO Valid: true
      SR-ERO hop count: 4
        Hop 1 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.1.3.3
          SID type: 20-bit label, Value: 23
        Hop 2 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.3.6.6
          SID type: 20-bit label, Value: 18
        Hop 3 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.6.7.7
          SID type: 20-bit label, Value: 20
        Hop 4 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.7.8.8
          SID type: 20-bit label, Value: 19

### We can see what labels are pushed to the wire: 

root@R1# run show route table inet.3 17.0.0.8/32 

inet.3: 7 destinations, 8 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

17.0.0.8/32        *[SPRING-TE/8] 00:03:03, metric 1, metric2 30
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 19, Push 20, Push 18(top)

### With tcmpdump we can see the same labels on the wire: 

15:58:36.512441 MPLS (label 18, exp 0, ttl 64) (label 20, exp 0, ttl 64) (label 19, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 59696, seq 4859, length 64

Let’s use the Loopbacks IP in our 2nd example:

### Reconfigure the LSP so that the Loopbacks are used instead: 

set protocols source-packet-routing segment-list R1-TO-R8-primary auto-translate
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 ip-address 17.0.0.3
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 ip-address 17.0.0.6
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 ip-address 17.0.0.7
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 ip-address 17.0.0.8

### But the system still thinks the IPs are interface IP. 

root@R1# run show spring-traffic-engineering lsp detail 
Name: R1-TO-R8
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 17.0.0.8
  Te-group-id: 0
  State: Down
    Path: R1-TO-R8-primary
    Path Status: NA
    Outgoing interface: NA
    Auto-translate status: Enabled Auto-translate result: Link not found
    Compute Status:Disabled , Compute Result:N/A , Compute-Profile Name:N/A
    BFD status: N/A BFD name: N/A
    BFD remote-discriminator: N/A
    Segment ID : 128 
    ERO Valid: true
      SR-ERO hop count: 4
        Hop 1 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.0.0.3
          SID type: None
        Hop 2 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.0.0.6
          SID type: None
        Hop 3 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.0.0.7
          SID type: None
        Hop 4 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.0.0.8
          SID type: None

### Let's tell JunOS these are node IPs or loopbacks: 

set protocols source-packet-routing segment-list R1-TO-R8-primary auto-translate
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 ip-address 17.0.0.3
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 label-type node
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 ip-address 17.0.0.6
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 label-type node
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 ip-address 17.0.0.7
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 label-type node
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 ip-address 17.0.0.8
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label-type node

[edit]
root@R1# commit 
[edit protocols source-packet-routing]
  'segment-list R1-TO-R8-primary'
    Under segment-list R1-TO-R8-primary, label-type node for 1st hop is supported only with inherit-label-nexthops enabled
error: configuration check-out failed

### Ok, Adding inherit-label-nexthops:

set protocols source-packet-routing segment-list R1-TO-R8-primary inherit-label-nexthops
set protocols source-packet-routing segment-list R1-TO-R8-primary auto-translate
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 ip-address 17.0.0.3
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 label-type node
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 ip-address 17.0.0.6
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 label-type node
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 ip-address 17.0.0.7
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 label-type node
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 ip-address 17.0.0.8
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label-type node

### Now it is working: 

root@R1# run show spring-traffic-engineering lsp detail 
Name: R1-TO-R8
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 17.0.0.8
  Te-group-id: 0
  State: Up
    Path: R1-TO-R8-primary
    Path Status: NA
    Outgoing interface: NA
    Auto-translate status: Enabled Auto-translate result: Success
    Compute Status:Disabled , Compute Result:N/A , Compute-Profile Name:N/A
    BFD status: N/A BFD name: N/A
    BFD remote-discriminator: N/A
    Segment ID : 128 
    ERO Valid: true
      SR-ERO hop count: 4
        Hop 1 (Loose): 
          NAI: IPv4 Node ID, Node address: 17.0.0.3
          SID type: 20-bit label, Value: 801003
        Hop 2 (Loose): 
          NAI: IPv4 Node ID, Node address: 17.0.0.6
          SID type: 20-bit label, Value: 801006
        Hop 3 (Loose): 
          NAI: IPv4 Node ID, Node address: 17.0.0.7
          SID type: 20-bit label, Value: 801007
        Hop 4 (Loose): 
          NAI: IPv4 Node ID, Node address: 17.0.0.8
          SID type: 20-bit label, Value: 801008


### We can see what labels are pushed to the wire: 

root@R1# run show route table inet.3 17.0.0.8/32 

inet.3: 7 destinations, 8 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

17.0.0.8/32        *[SPRING-TE/8] 00:00:35, metric 1, metric2 30
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 801008, Push 801007, Push 801006(top)

### With tcmpdump we can see the same labels on the wire: 

16:11:13.674433 MPLS (label 801006, exp 0, ttl 64) (label 801007, exp 0, ttl 64) (label 801008, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 59696, seq 5612, length 64

Or we can use a combination:

### Alternatively we can remove inherit-label-nexthops and use an interface IP for hop 1 and 3:

root@R1# show | compare 
[edit protocols source-packet-routing segment-list R1-TO-R8-primary]
-    inherit-label-nexthops;
[edit protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3]
-     ip-address 17.0.0.3;
+     ip-address 17.1.3.3;
-     label-type {
-         node;
-     }
[edit protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7]
-     ip-address 17.0.0.7;
+     ip-address 17.6.7.7;
-     label-type {
-         node;
-     }

### So the config looks like this: 

set protocols source-packet-routing segment-list R1-TO-R8-primary auto-translate
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-1-R3 ip-address 17.1.3.3
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 ip-address 17.0.0.6
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-2-R6 label-type node
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-3-R7 ip-address 17.6.7.7
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 ip-address 17.0.0.8
set protocols source-packet-routing segment-list R1-TO-R8-primary HOP-4-R8 label-type node

### The LSP is UP:

root@R1# run show spring-traffic-engineering lsp detail 
Name: R1-TO-R8
  Tunnel-source: Static configuration
  Tunnel Forward Type: SRMPLS
  To: 17.0.0.8
  Te-group-id: 0
  State: Up
    Path: R1-TO-R8-primary
    Path Status: NA
    Outgoing interface: ge-0/0/2.0
    Auto-translate status: Enabled Auto-translate result: Success
    Compute Status:Disabled , Compute Result:N/A , Compute-Profile Name:N/A
    BFD status: N/A BFD name: N/A
    BFD remote-discriminator: N/A
    Segment ID : 128 
    ERO Valid: true
      SR-ERO hop count: 4
        Hop 1 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.1.3.3
          SID type: 20-bit label, Value: 23
        Hop 2 (Loose): 
          NAI: IPv4 Node ID, Node address: 17.0.0.6
          SID type: 20-bit label, Value: 801006
        Hop 3 (Strict): 
          NAI: IPv4 Adjacency ID, 0.0.0.0 -> 17.6.7.7
          SID type: 20-bit label, Value: 20
        Hop 4 (Loose): 
          NAI: IPv4 Node ID, Node address: 17.0.0.8
          SID type: 20-bit label, Value: 801008

### The labels pushed to the wire: 

root@R1# run show route table inet.3 17.0.0.8/32 

inet.3: 7 destinations, 8 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

17.0.0.8/32        *[SPRING-TE/8] 00:02:10, metric 1, metric2 30
                    >  to 17.1.3.3 via ge-0/0/2.0, Push 801008, Push 20, Push 801006(top)

### And the same labels as seen with the tcpdump: 

16:22:35.989263 MPLS (label 801006, exp 0, ttl 64) (label 20, exp 0, ttl 64) (label 801008, exp 0, ttl 64) (label 16, exp 0, [S], ttl 64) IP 192.168.1.1 > 192.168.8.1: ICMP echo request, id 59696, seq 6290, length 64

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External Resources:

• Traffic Engineering with Manual User Segment Configuration | Junos OS
• Segment Routing LSP Configuration | Junos OS
• Example: Configuring Static Segment Routing Label Switched Path | Junos OS