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MPLS Connection Checking

Use either the J-Web ping MPLS diagnostic tool or the CLI ping mpls command to diagnose the state of label-switched paths (LSPs), Layer 2 and Layer 3 virtual private networks (VPNs), and Layer 2 circuits.

When you use the ping MPLS feature from a Services Router operating as the inbound (ingress) node at the entry point of an LSP or VPN, the router sends probe packets into the LSP or VPN. Based on how the LSP or VPN outbound (egress) node at the remote endpoint of the connection replies to the probes, you can determine the connectivity of the LSP or VPN.

Each probe is an echo request sent to the LSP or VPN exit point as an MPLS packet with a UDP payload. If the outbound node receives the echo request, it checks the contents of the probe and returns a value in the UDP payload of the response packet. If the Services Router receives the response packet, it reports a successful ping response.

Responses that take longer than 2 seconds are identified as failed probes.

Table 192 summarizes the options for using either the J-Web ping MPLS diagnostic tool or the CLI ping mpls command to display information about MPLS connections in VPNs and LSPs.

Table 192: Options for Checking MPLS Connections

J-Web Ping MPLS Tool	ping mpls Command	Purpose	Additional Information
Ping RSVP-signaled LSP	ping mpls rsvp	Checks the operability of an LSP that has been set up by the Resource Reservation Protocol (RSVP). The Services Router pings a particular LSP using the configured LSP name.	When an RSVP-signaled LSP has several paths, the Services Router sends the ping requests on the path that is currently active.
Ping LDP-signaled LSP	ping mpls ldp	Checks the operability of an LSP that has been set up by the Label Distribution Protocol (LDP). The Services Router pings a particular LSP using the forwarding equivalence class (FEC) prefix and length.	When an LDP-signaled LSP has several gateways, the Services Router sends the ping requests through the first gateway. Ping requests sent to LDP-signaled LSPs use only the master routing instance.
Ping LSP to Layer 3 VPN prefix	ping mpls l3vpn	Checks the operability of the connections related to a Layer 3 VPN. The Services Router tests whether a prefix is present in a provider edge (PE) router's VPN routing and forwarding (VRF) table, by means of a Layer 3 VPN destination prefix.	The Services Router does not test the connection between a PE router and a customer edge (CE) router.
Locate LSP using interface name	ping mpls l2vpn interface	Checks the operability of the connections related to a Layer 2 VPN. The Services Router directs outgoing request probes out the specified interface.	For information about interface names, See the interface naming conventions in the JUNOS Software Interfaces and Routing Configuration Guide.
Instance to which this connection belongs	ping mpls l2vpn instance	Checks the operability of the connections related to a Layer 2 VPN. The Services Router pings on a combination of the Layer 2 VPN routing instance name, the local site identifier, and the remote site identifier, to test the integrity of the Layer 2 VPN circuit (specified by the identifiers) between the inbound and outbound PE routers.
Locate LSP from interface name	ping mpls l2circuit interface	Checks the operability of the Layer 2 circuit connections. The Services Router directs outgoing request probes out the specified interface.
Locate LSP from virtual circuit information	ping mpls l2circuit virtual-circuit	Checks the operability of the Layer 2 circuit connections. The Services Router pings on a combination of the IPv4 prefix and the virtual circuit identifier on the outbound PE router, testing the integrity of the Layer 2 circuit between the inbound and outbound PE routers.
Ping end point of LSP	ping mpls lsp-end-point	Checks the operability of an LSP endpoint. The Services Router pings an LSP endpoint using either an LDP FEC prefix or an RSVP LSP endpoint address.

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