Table Of Contents
MPLS Traffic Engineering (TE)—IP Explicit Address Exclusion
This feature modules describes MPLS traffic engineering IP explicit address exclusion for Release 12.0(14)S.
This document contains the following sections:
The MPLS traffic engineering Internet Protocol (IP) explicit address exclusion feature provides a means to exclude a link or node from the path for an MPLS traffic engineering label-switched path (LSP).
The feature is accessible via the ip explicit-path command that allows you to create an IP explicit path and enter a configuration submode for specifying the path. The feature adds to the submode commands the exclude-address command for specifying addresses to exclude from the path.
If the exclude-address for an MPLS traffic engineering LSP identifies a flooded link, the constraint-based shortest path first (CSPF) routing algorithm doesn't consider that link when computing paths for the LSP. If the exclude-address specifies a flooded MPLS traffic engineering router ID, the CSPF routing algorithm doesn't allow paths for the LSP to traverse the node identified by the router ID.
This feature is useful when you want MPLS traffic engineering LSPs to avoid certain links and nodes.
MPLS traffic engineering will accept an IP explicit path comprised of either all exclude-addresses configured by the exclude-address command or all include-addresses configured by the next-address, but not a combination of both.
Related Features and Technologies
The IP explicit address exclusion feature is related to
•MPLS traffic engineering
•Cisco Express Forwarding (CEF)
Refer to the Cisco IOS Release 12.0(10)ST MPLS Traffic Engineering and Enhancements manual.
MPLS traffic engineering IP explicit address exclusion is supported on the following platforms:
•Cisco 7200 series (including the Cisco 7202, Cisco 7204, Cisco 7204 VXR, Cisco 7206, and Cisco 7206 VXR)
•Cisco 7500 series (including the Cisco 7505, Cisco 7507, Cisco 7513, and Cisco 7576)
•Cisco GSR 12000 series (including the Cisco 12008, Cisco 12012, and Cisco 12016)
Supported Standards, MIBs, and RFCs
This feature does not support any new or modified standards.
This feature does not support any new or modified MIBs.
To obtain lists of MIBs supported by platform and Cisco IOS release and to download MIB modules, go to the Cisco MIB web site on Cisco Connection Online (CCO) at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
This feature does not support any new or modified RFCs.
Your network must support the following Cisco IOS features in order to support IP explicit address exclusion:
•IP Cisco Express Forwarding (CEF)
•Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF)
To enable IP explicit address exclusion for use with traffic engineering tunnels, perform the following steps:
•Enter the ip explicit-path command to configure an explicit path and enter the exclude-address command to specify the addresses to be excluded from the path.
•Configure an MPLS traffic engineering tunnel to use the explicit path as one of its path options.
Configuring IP Explicit Address Exclusion
Configuring an MPLS Traffic Engineering Tunnel
To configure an MPLS traffic engineering tunnel, perform these steps in interface configuration mode.
Note To configure a path option that specifies an exclude address in Step 6, specify the explicit keyword (not the dynamic keyword) and specify an IP explicit path configured according to the steps in "Configuring IP Explicit Address Exclusion."
Verifying IP Explicit Address Exclusion
This example illustrates how to configure an MPLS traffic engineering tunnel with two path options: a preferred explicit path with an exclude-address and a backup dynamic path.
First, configure the IP explicit path named "OmitR12" which excludes the router with router ID 220.127.116.11router(config)# ip explicit-path name OmitR12router(cfg-ip-expl-path)# excrouter(cfg-ip-expl-path)# exclude-address 18.104.22.168Explicit Path name OmitR12:1: exclude-address 22.214.171.124router(cfg-ip-expl-path)# end
To verify the configuration of the explicit path, use the show ip explicit-path command:router# show ip explicit-paths name OmitR12PATH OmitR12 (loose source route, path complete, generation 3)1: exclude-address 126.96.36.199router#
Note The person performing the configuration must know the router IDs for LSRs (nodes) in the network; in this example, that 188.8.131.52 is a router ID. Otherwise, it will not be apparent whether the specified address is the IP address of a link or a router ID.
Next, configure Tunnel11 with its two options, where the preferred path option is the ip explicit path "OmitR2":router(config)# interface Tunnel11router(config-if)# ip unnumbered Loopback0router(config-if)# tunnel destination 184.108.40.206router(config-if)# tunnel mode mpls traffic-engrouter(config-if)# tunnel mpls traffic-eng path-option 1 explicit name OmitR12router(config-if)# tunnel mpls traffic-eng path-option 2 dynamic
Note There are additional commands for configuring properties for traffic engineering tunnels such as bandwidth, priority, and so forth. For descriptions of those commands, refer to the MPLS Traffic Engineering and Enhancements manual.
This section documents the exclude-address command. All other commands used with this feature are documented in the Cisco IOS Release 12.0 and Release 12.1 command reference publications.
An IP explicit path is a list of IP addresses, each representing a node or link in the explicit path. To exclude an address from an IP explicit path, use the exclude-address command after entering explicit path configuration mode via the ip-explicit path command. To remove an address exclusion from an IP explicit path use the no index command.
no index number
Excludes an address from subsequent partial path segments. You can enter the IP address of a link or the router ID of a node.
Removes the specified address exclusion from an IP explicit path.
Addresses are not excluded from an IP explicit path unless explicitly excluded by the exclude-address command.
If you enter the exclude-address command and specify the IP address of a link, the constraint-based SPF routine does not consider that link when it sets up MPLS traffic engineering paths. If the excluded address is a flooded MPLS traffic engineering router ID, the constraint-based SPF routine does not consider that entire node. The person performing the configuration must know the router IDs of the routers because it will not be apparent whether the specified number is for a link or for a node.
Note MPLS traffic engineering will accept an IP explicit path comprised of either all exclude-addresses configured by the exclude-address command or all include-addresses configured by the next-address, but not a combination of both.
The following example shows how to create a IP explicit path with identifier 500 and enter the explicit path subcommand mode to configure the path:Router(config)# ip explicit-path identifier 500Router(config-ip-expl-path)#
The following continues by showing how to exclude IP addresses 10.0.0.125 and 10.0.0.135 from IP explicit path 500:Router(config-ip-expl-path)# exclude-address 10.0.0.125Explicit Path identifier 500:1: exclude-address 10.0.0.125Router(config-ip-expl-path)# exclude-address 10.0.0.135Explicit Path identifier 500:1: exclude-address 10.0.0.1252: exclude-address 10.0.0.135Router(config-ip-expl-path)# endRouter#
To remove IP address 10.0.0.125 from the excluded addresses for explicit path 500, use the following commands:Router(config)# ip explicit-path identifier 500Router(cfg-ip-expl-path)# no index 1Explicit Path identifier 500:2: exclude-address 10.0.0.135Router(cfg-ip-expl-path)# end
Enters the subcommand mode for Internet protocol (IP) explicit paths and creates or modifies a specified path.
CEF—Cisco express forwarding. A means for accelerating the forwarding of packets within a router, by storing route lookup information in several data structures instead of in a route cache.
IP explicit path—A list of IP addresses, each representing a node or link in the explicit path.
link—Network communications channel consisting of a circuit or transmission path and all related equipment between a sender and a receiver. Sometimes referred to as a line or a transmission link.
MPLS—Multiprotocol label switching (formerly known as tag switching). A method for directing packets primarily through Layer 2 switching rather than Layer 3 routing. In MPLS, packets are assigned short fixed-length labels at the ingress to an MPLS cloud by using the concept of forwarding equivalence classes. Within the MPLS domain, the labels are used to make forwarding decisions mostly without recourse to the original packet headers.
node—Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be interconnected by links, and serve as control points in the network.