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Checking MPLS Connections

You can use the ping MPLS diagnostic tool to diagnose the state of label-switched paths (LSPs), Layer 2 and Layer 3 VPNs, and Layer 2 circuits.

When you issue a command 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.

Alternatively, you can use the CLI commands ping mpls, ping mpls l2circuit, ping mpls l2vpn, and ping mpls l3vpn. For more information, see the JUNOS Protocols, Class of Service, and System Basics Command Reference.

Options for Checking MPLS Connections

The ping MPLS diagnostic tool has eight options for returning information about MPLS connections in VPNs and LSPs. Table 59 lists and explains the options for checking MPLS connections.

Table 59: Options for Checking MPLS Connections

Ping MPLS Tool	Purpose	Additional Information
Ping RSVP-signaled LSP	Checks the operability of an LSP that has been set up by 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	Checks the operability of an LSP that has been set up using 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	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	Checks the operability of the connections related to a Layer 2 VPN. The Services Router directs outgoing request probes out the specified interface.
Instance to which this connection belongs	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	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	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	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.

Ping MPLS Requirements

Before using the ping MPLS tool, make sure that your network meets the following requirements:

To process ping MPLS requests, the remote endpoint of the VPN or LSP must be configured appropriately. You must enable MPLS on the receiving interface of the outbound node for the VPN or LSP. If MPLS is not enabled, the remote endpoint drops the incoming request packets and returns an “ICMP host unreachable” message to the Services Router. To enable MPLS on an interface, see the J-series Services Router Configuration Guide.
The loopback address (lo0) on the outbound node must be configured as 127.0.0.1. If this interface address is not configured correctly, the outbound node does not have this forwarding entry. It drops the incoming request packets and returns a “host unreachable” message to the Services Router. If the outbound node is a Services Router, see the J-series Services Router Configuration Guide to configure the loopback address.
The source IP address you specify for a set of probes must be an address configured on one of the Services Router interfaces. If it is not a valid Services Router address, the ping request fails with the error message “Can't assign requested address.”

Using the Ping MPLS Tool

To use the ping MPLS tool:

Select Diagnose>Ping MPLS from the task bar.
Next to the ping MPLS option you want to use, click the expand icon (see Figure 14).
Enter information into the Ping MPLS page, as described in Table 60.
Click Start.
Table 61 summarizes the output fields of the display.
To stop the ping operation before it is complete, click OK.

Figure 14: Ping MPLS Page

Image s020042.gif

Table 60: J-Web Ping MPLS Summary

Field	Function	Your Action
Ping RSVP-signaled LSP
LSP Name	Identifies the LSP to ping.	Type the name of the LSP to ping.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send. The default is 5 requests.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.
Ping LDP-signaled LSP
FEC Prefix	Identifies the LSP to ping.	Type the forwarding equivalence class (FEC) prefix and length of the LSP to ping.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send. The default is 5 requests.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.
Ping LSP to Layer 3 VPN prefix
Layer 3 VPN Name	Identifies the Layer 3 VPN to ping.	Type the name of the VPN to ping.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send. The default is 5 requests.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.
VPN Prefix	Identifies the IP address prefix and length of the Layer 3 VPN to ping.	Type the IP address prefix and length of the VPN to ping.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Locate LSP using interface name
Interface	Specifies the interface on which the ping requests are sent.	From the drop-down list, select the Services Router interface on which ping requests are sent. If you select any, the ping requests are sent on all interfaces.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send. The default is 5 requests.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.
Instance to which this connection belongs
Layer 2VPN Name	Identifies the Layer 2 VPN to ping.	Type the name of the VPN to ping.
Remote Site Identifier	Specifies the remote site identifier of the Layer 2 VPN to ping.	Type the remote site identifier for the VPN.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Local Site Identifier	Specifies the local site identifier of the Layer 2 VPN to ping.	Type the local site identifier for the VPN.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send. The default is 5 requests.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.
Locate LSP from interface name
Interface	Specifies the interface on which the ping requests are sent.	From the drop-down list, select the Services Router interface on which ping requests are sent. If you select any, the ping requests are sent on all interfaces.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send. The default is 5 requests.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.
Locate LSP from virtual circuit information
Remote Neighbor	Identifies the remote neighbor (PE router) within the virtual circuit to ping.	Type the IP address of the remote neighbor within the virtual circuit.
Circuit Identifier	Specifies the virtual circuit identifier for the Layer 2 circuit to ping.	Type the virtual circuit identifier for the Layer 2 circuit.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.
Ping end point of LSP
VPN Prefix	Identifies the LSP endpoint to ping.	Type either the LDP FEC prefix and length or the RSVP LSP endpoint address for the LSP to ping.
Source Address	Specifies the source address of the ping request packet.	Type the source IP address—a valid address configured on a Services Router interface.
Count	Specifies the number of ping requests to send.	From the drop-down list, select the number of ping requests to send.
Detailed Output	Requests the display of extensive rather than brief ping output.	Select the check box to display detailed output.

Table 61: J-Web Ping MPLS Results Summary

Field	Description
Exclamation point (!)	Echo reply was received.
Period (.)	Echo reply was not received within the timeout period.
x	Echo reply was received with an error code. Errored packets are not counted in the received packets count and are accounted for separately.
number packets transmitted	number—Number of ping requests (probes) sent to a host.
number packets received	number—Number of ping responses received from a host.
percentage packet loss	percentage—Number of ping responses divided by the number of ping requests, specified as a percentage.

If the Services Router does not receive ping responses from the destination host (the output shows a packet loss of 100 percent), one of the following might apply:

The host is not operational.
There are network connectivity problems between the Services Router and the host.
The host might be configured to ignore echo requests.
The host might be configured with a firewall filter that blocks echo requests or echo responses.
The size of the echo request packet exceeds the MTU of a host along the path.
The outbound node at the remote endpoint is not configured to handle MPLS packets.
The remote endpoint's loopback address is not configured to 127.0.0.1.

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