Cisco 3845 Software Guide - Page 823

Chapter 34 Configuring MPLS, MPLS VPN, MPLS OAM, and EoMPLS Understanding MPLS OAM LSP Ping • To allow interoperability between these IETF RFC 4379 drafts, the revision keyword was added to enable Cisco IOS releases to support the existing draft changes and any changes from future versions of the IETF LSP Ping draft. The switch supports revision 2 and RFC 4329 Compliant. In addition, these other features have been added: • Echo request return codes have been enhanced for better fault isolation. • You can use the no mpls oam global configuration command to disable the MPLS OAM subsystem when MPLS is running. • You can configure the maximum number of labels in a label stack for load balancing. • The switch supports IP load balancing, up to a total of four next-hop paths. With the IP license, the switch supports up to sixteen next-hop paths. Each path supports up to four Equal Cost Routing (ECR) multipaths. • The switch now supports LSP tree trace, using the trace mpls multipath. privileged EXEC command to trace all possible paths of an LSP network between the ingress and egress routers by using downstream mapping. Enhancements to the IP SLAs MPLS LSP Health Monitor include: • Entering the auto ip sla mpls-lsp-monitor global configuration command automatically configures ping and traceroute boundaries • Entering the path-discover command in auto IP SLA MPLS parameter configuration mode configures equal cost multipath (ECMP) tree trace. VPN end points are automatically discovered and ping or traceroute actions are automatically generated for each provider edge router. • For more information on configuring the LSP Health Monitor, go to this URL: http://www.cisco.com/en/US/docs/ios/ipsla/configuration/guide/sla_lsp_mon_autodisc.html MPLS LSP ping uses MPLS echo request and reply packets, similar to Internet Control Message Protocol (ICMP) echo request and reply messages, to validate an LSP. ICMP echo request and reply messages validate IP networks; MPLS OAM echo and reply messages validate MPLS LDP networks. The LSP ping and trace functions use IPv4 UDP packets with UDP port number 3503. You can use MPLS LSP ping to validate IPv4 LDP or Forwarding Equivalence Classes (FECs) by using the ping mpls privileged EXEC command. The MPLS echo request packet is sent to a target router by using the label stack associated with the FEC to be validated. The source address of the LSP echo request is the IP address of the LDP router generating the LSP request. The destination IP address is a 127.x.y.z/8 address, which prevents the IP packet from being switched to its destination if the LSP is broken. The 127.0.0.x destination address range prevents the OAM packets from exiting the egress provider-edge router, which keeps them from leaking from the service-provider network to the customer network. In response to an MPLS echo request, an MPLS echo reply is forwarded as an IP packet by using IP, MPLS, or a combination of both. The source address of the MPLS echo-reply packet is an address obtained from the router generating the echo reply. The destination address is the source address of the router that originated the MPLS echo-request packet. The MPLS echo-reply destination port is the echo-request source port. OL-23400-01 Cisco ME 3800X and 3600X Switch Software Configuration Guide 34-43