The Segment Routing-OAM Support feature provides support for Nil-FEC LSP Ping/Trace functionality. Nil-FEC LSP Ping/Trace functionality support Segment Routing and MPLS Static. It also acts as an additional diagnostic tool for all other LSP types. This feature allows operators to provide the ability to freely test any label stack by allowing them to specify the following:

• Label stack
• Outgoing interface
• Nexthop address

In the case of segment routing, each segment nodal label and adjacent label along the routing path is put into the label stack of an echo request message from initiator Label Switch Router (LSR); MPLS data plane forward this packet to the label stack target, and the label stack target reply the echo message back.

The LSP Ping/Traceroute is used in identifying LSP breakages. The nil-fec target type can be used to test the connectivity for a known label stack. Follow the existing LSP ping procedure (for more information, refer MPLS LSP Ping/Traceroute), with the following modifications:

• Build the echo request packet with the given label stack;
• Append explicit null label at the bottom of the label stack;
• Build echo request FTS TLV with target FEC Nil FEC and label value set to the bottom label of the label stack, which is explicit-null.

The Nil-FEC LSP ping and traceroute operation are simply extension of regular MPLS ping and trace route. nil-fec labels <label, label...> is added to the ping mpls command. This command sends an echo request message with MPLS label stack as specified, and add another explicit null at bottom of the stack.

ping mpls
   {{ipv4 <target>/<mask> [fec-type {bgp | generic | ldp}] |
    {pseudowire <peer addr> <vc-id> [segment<segment-number>]} |
    {traffic-eng {<tunnel interface> |
          {p2p <sender> <endpoint>
    <tun-id> <ex-tun-id> <lspid>} |
          {p2mp <p2mp-id> <sender>
     <tun-id><ex-tun-id> <lspid>}} |
{tp <tunnel-tp interface> lsp <working | protect | active>}} |
  {mldp {p2mp | mp2mp}
{{ipv4 <source> <group>} |
 {ipv6 <source> <group>} |
 {vpnv4 <rd> <source> <group>} |
 {vpnv6 <rd> <source> <group>} |
 {hex <opaque type> <opaque value>} |
  {mdt <vpnid> <mdt-num>} |
 {static-id <lsp-identifier>} |
 {global-id <global-identifier>}}} |
 {nil-fec {labels <comma separated labels>}}
 [repeat <count>]
 [size <size> | sweep <min_size> <max_size> <increment>]
 [timeout <seconds>]
 [interval <milliseconds>]
 [destination <addr_start> [<addr_end> [<addr_incr_mask> | <addr_incr>]]]
 [source <addr>]
 [exp <exp-value>]
 [pad <pattern>]
 [ttl <ttl>]
 [reply [mode [ipv4 | router-alert | no-reply]]
 [dscp <dscp-bits>]
 [pad-tlv]]
 [verbose]
 [force-explicit-null]
 [force-disposition ra-label]
 [output {interface <tx-interface>} [nexthop <nexthop ip addr>]]
[{dsmap | ddmap [l2ecmp]} [hashkey {none | {ipv4 | ipv4-label-set {bitmap <bitmap_size>}}]
 [flags {fec | ttl}]
 [segment {all | <lower-segment-number> [upper-segment-number]}
 [jitter <milliseconds>]
 [responder-id <ip addr> | egress <ipaddr>]
   NOTE: responder-id for mldp/ egress for p2mp te
 [entropy-label <label-value>]

For more information, see ping mpls .

trace mpls
   {{ipv4 <target>/<mask> [fec-type {bgp | generic | ldp}]} |
    {traffic-eng {<tunnel interface> |
          {p2p <sender> <endpoint>
       <tun-id> <ex-tun-id> <lspid>} |
      {p2mp <p2mp-id> <sender>
     <tun-id><ex-tun-id> <lspid>}} |
    {mldp {p2mp | mp2mp}
  {{ip <source> <group>} |
   {vpn <rd> [<source> <group>]} |
   {hex <opaque type> <opaque value>} |
    {mdt <vpnid> <mdt-num>} |
   {static-id <lsp-identifier>} |
   {global-id <global-identifier>}}}
    {pseudowire <next-pe-address> <pwid> [segment
     <segment-number/lower-segment-number>[<upper-segment-limit>]]} |
    {tp <tunnel-tp interface> lsp <working | protect | active>}} |
   {nil-fec {labels <comma separated labels>}}
   [timeout <seconds>]
   [destination <addr_start> [<addr_end> [<addr_incr_mask> | <addr_incr>]]]
   [source <addr> ]
   [exp <exp-value>]
   [ttl <ttl-max>]
   [reply [mode [ipv4 | router-alert | no-reply]]
   [dscp <dscp-bits>]
   [pad-tlv]]
   [force-explicit-null]
   [output {interface <tx-interface>} [nexthop <nexthop ip addr>]]
   [flags {fec | ttl}]
   [entropy-label <label-value>]
[hashkey ipv4 | ipv4-label-set {bitmap <bitmap_size>}]

For more information, see traceroute mpls .