Cisco ASR 900 Series User Manual

Table 10: Reply Mode Options for a Responding Device
DescriptionOption
Reply with an IPv4 User Datagram Protocol (UDP)
packet (default). This is the most common reply mode
selected for use with an MPLS LSP Ping and
Traceroute command when you want to periodically
poll the integrity of a label switched path (LSP).
With this option, you do not have explicit control over
whether the packet traverses IP or MPLS hops to
reach the originator of the MPLS echo request.
If the headend device fails to receive a reply, select
the router-alert option, “Reply with an IPv4 UDP
packet with a router alert.”
The responding device sets the IP precedence of the
reply packet to 6.
You implement this option using the reply mode ipv4
keywords.
ipv4
Reply with an IPv4 UDP packet with a device alert.
This reply mode adds the router alert option to the IP
header. This forces the packet to be special handled
by the Cisco device at each intermediate hop as it
moves back to the destination.
This reply mode is more expensive, so use the
router-alert option only if you are unable to get a reply
with the ipv4 option, “Reply with an IPv4 UDP
packet.”
You implement this option using the reply mode
router-alert keywords
router-alert
The reply with an IPv4 UDP packet implies that the device should send an IPv4 UDP packet in reply to an
MPLS echo request. If you select the ipv4 reply mode, you do not have explicit control over whether the
packet uses IP or MPLS hops to reach the originator of the MPLS echo request. This is the mode that you
would normally use to test and verify LSPs.
The reply with an IPv4 UDP packet that contains a device alert forces the packet to go back to the destination
and be processed by the Route Processor (RP) process switching at each intermediate hop. This bypasses
hardware/line card forwarding table inconsistencies. You should select this option when the originating
(headend) devices fail to receive a reply to the MPLS echo request.
You can instruct the replying device to send an echo reply with the IP router alert option by using one of the
following commands:
ping mpls
{ipv4 destination-address/destination-mask | pseudowire ipv4-address
vc-idvc-id | traffic-engtunnel-interface tunnel-number}
reply mode router-alert
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
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MPLS LSP Ping, Traceroute, and AToM VCCV
Command Options for ping mpls and trace mpls

Cisco ASR 900 Series Specifications

General

Product Family	ASR 900 Series
Category	Network Router
Connectivity Technology	Wired
Switching Capacity	Varies by model
Memory	Varies by model
Operating System	Cisco IOS XE
Dimensions	Varies by model
Weight	Varies by model
Form Factor	Modular
Supported Interfaces	Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet, T1/E1, T3/E3, OC-3/STM-1, OC-12/STM-4, OC-48/STM-16
Ports	Varies by model
Data Link Protocol	Ethernet, Fast Ethernet, Gigabit Ethernet
Network / Transport Protocol	TCP/IP, UDP
Routing Protocol	BGP, OSPF, IS-IS, RIP, EIGRP, MPLS
Remote Management Protocol	SNMP, CLI, SSH
Features	MPLS, QoS, IPv6, NetFlow, ACLs, VRF
Power Supply	AC or DC
Operating Temperature	0 to 40°C
Storage Temperature	-40 to 70°C (-40 to 158°F)
Humidity	5% to 95% (non-condensing)

Summary

Multiprotocol Label Switching (MPLS) on Cisco Routers

Finding Feature Information

Locates information about features, caveats, and release notes.

Information About MPLS

Provides an overview of MPLS functionality and its role in networks.

How to Configure MPLS

Explains basic configuration for MPLS switching and forwarding.

Additional References

Lists related documents for Cisco IOS commands and MPLS commands.

Feature Information for MPLS on Cisco Routers

Details software release information for MPLS features.

Glossary

Defines key terms and acronyms used in the document.

MPLS Transport Profile

Restrictions for MPLS-TP on the Cisco ASR 900 Series Routers

Lists limitations and unsupported features for MPLS-TP on specific routers.

Information About MPLS-TP

Explains how MPLS Transport Profile works, including LSPs and pseudowires.

How to Configure MPLS Transport Profile

Provides steps for configuring MPLS Transport Profile, including label ranges.

Configuration Examples for MPLS Transport Profile

Offers practical examples of MPLS Transport Profile configuration scenarios.

MPLS Multilink PPP Support

Prerequisites for MPLS Multilink PPP Support

Lists requirements for enabling MPLS Multilink PPP support.

Restrictions for MPLS Multilink PPP Support

Details limitations on multilink bundles and members per bundle.

Information About MPLS Multilink PPP Support

Describes Layer 3 VPN features and QoS features supported for Multilink PPP.

How to Configure MPLS Multilink PPP Support

Guides through configuring MPLS Multilink PPP support, including bundle creation.

Configuration Examples for MPLS Multilink PPP Support

Provides sample configurations for MPLS Multilink PPP in various network scenarios.

MPLS LSP Ping, Traceroute, and AToM VCCV

Prerequisites for MPLS LSP Ping, Traceroute, and AToM VCCV

Lists prerequisites before using MPLS LSP Ping, Traceroute, and AToM VCCV features.

Restrictions for MPLS LSP Ping, Traceroute, and AToM VCCV

Details limitations on using MPLS LSP Ping and Traceroute for specific applications like AToM and VPNs.

Information About MPLS LSP Ping, Traceroute, and AToM VCCV

Explains MPLS LSP Ping operation, echo request/reply paths, and packet handling.

Command Options for ping mpls and trace mpls

Describes command options and arguments for MPLS LSP Ping and Traceroute.

Selection of FECs for Validation

Explains how to select Forwarding Equivalence Classes (FECs) for LSP validation.

Reply Mode Options for MPLS LSP Ping and Traceroute

Controls how the responding device replies to MPLS echo requests.

Packet Handling Along Return Path with an IP MPLS Router Alert

Describes how IP and MPLS packets with router alert options are handled.

Other MPLS LSP Ping and Traceroute Command Options

Details additional command options for MPLS LSP Ping and Traceroute.

MPLS LSP Ping and Traceroute Returns a Q

Troubleshoots issues when MPLS echo replies return a 'Q' code, indicating packet transmission failure.

Load Balancing for IPv4 LDP LSPs

Explains how MPLS uses source/destination addresses for load balancing.

NSR LDP Support

Finding Feature Information

Locates information about features, caveats, and release notes for NSR LDP Support.

Prerequisites for NSR LDP Support

Lists requirements for NSR LDP Support to function correctly.

Information About NSR LDP Support

Details the roles of standby RP and LDP, and NSR operation states.

How to Configure NSR LDP Support

Provides steps to enable and configure NSR LDP Support.

Configuration Examples for NSR LDP Support

Shows sample configurations for NSR LDP Support, including verification steps.

Additional References for NSR LDP Support

Lists related documents and technical assistance resources for NSR LDP Support.

Feature Information for NSR LDP Support

Provides release-specific information for NSR LDP Support features.

VPLS Configuration over MPLS-TP

VPLS over MPLS-TP

Provides an overview of VPLS implementation over MPLS-TP.

Configuring VPLS over MPLS-TP

Guides through the configuration steps for VPLS over MPLS-TP.

Verifying the Configuration

Details commands for verifying VPLS configuration and debugging.

Configuration Examples

Offers practical examples for configuring VPLS over MPLS-TP.

Feature Information for VPLS Configuration over MPLS-TP

Lists software release information for VPLS over MPLS-TP features.

Circuit Emulation Service over UDP

Finding Feature Information

Locates information about features, caveats, and release notes for Circuit Emulation over UDP.

Restrictions for Circuit Emulation Service over UDP

Lists limitations and unsupported features for Circuit Emulation Service over UDP.

Information About Circuit Emulation Service over UDP

Explains CES overview, pseudowire emulation, and CESoPSN mode.

How to Configure Circuit Emulation Service over UDP

Guides through configuring Circuit Emulation Service over UDP.

Structure-Agnostic TDM over Packet over UDP

Details the Structure-Agnostic TDM over Packet (SAToP) encapsulation method.

How to Configure Structure-Agnostic TDM over Packet

Guides through configuring Structure-Agnostic TDM over Packet (SAToP).

Example Verifying the Configuration of Structure-Agnostic TDM over Packet

Demonstrates how to verify the SAToP configuration.

Flex LSP Overview

Signaling Methods and Object Association for Flex LSPs

Explains association signaling methods for bidirectional LSPs in Flex LSP.

Associated Bidirectional Non Co-routed and Co-routed LSPs

Overviews associated bidirectional LSPs, covering non co-routed and co-routed types.

Restrictions for Flex LSP

Lists limitations and recommendations for Flex LSP deployments.

How to Configure Co-routed Flex LSPs

Guides through configuring co-routed bidirectional Flex LSPs, including setup steps.

How to Configure Non Co-routed Inter-area Flex LSP Tunnels

Details configuration steps for non co-routed inter-area Flex LSP tunnels.

Flex LSP Phase 2

Covers features supported in Flex LSP Phase 2, like SRLG protection and ECMP.

Flex LSP SRLG and Exclude Option for Explicit Path

Explains how to configure SRLG and exclude options for Flex LSP explicit paths.

Flex LSP Non-Revertive 1:1 Path Protection

Guides on configuring non-revertive path protection for Flex LSP.

Flex LSP Sticky

Guides on configuring the sticky option for Flex LSP path protection.

Flex LSP Hop Count and Cost-Max Limit

Explains configuring hop count and accumulated path cost limits for Flex LSPs.

Flex LSP ECMP min-fill, max-fill, random

Details configuring ECMP tie-breakers like min-fill, max-fill, and random for Flex LSPs.

Restore Path Option

Explains how to configure and verify the restore path option for Flex LSP tunnels.