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Express Segment LSP Configuration

Establish End-to-End Segment Routing Path Using Express Segments

Learn about the benefits, use cases, and overview of how express segments work to establish an end-to-end segment routing path in a multi-domain network.

Benefits of Express Segments

  • Express segments are a segment routing (SR) abstraction of an underlay path. Express segments facilitate the establishment of end-to-end SR paths using any underlay technology.

    In Figure 1, Domain 2 leverages its RSVP-TE underlay LSPs for traffic engineering management and presents those underlay RSVP-TE LSPs as express segments to the adjacent domains (Domain 1 and Domain 3), therefore enabling end-to-end SR-TE path establishment.

    Figure 1: Multi-Domain End-to-End SR-TE with RSVP UnderlayMulti-Domain End-to-End SR-TE with RSVP Underlay
  • Express segments implicitly reduce the size of the SR segment list by compressing them (segment lists) to, at a minimum, one segment ID (SID)/label per domain. This becomes useful when end-to-end traffic engineered constraints would otherwise result in a segment list that exceeds the ingress router's label imposition capabilities. This also becomes beneficial when one or more domains are already implementing SR-TE for traffic engineered path management.

    In Figure 2, you can see Domain 2 is using SR-TE and how the use of express segments enables PE1 device to use three labels to traverse the multi-domain network instead of five.

    Figure 2: Multi-Domain End-to-End SR-TE with Reduced Label StackMulti-Domain End-to-End SR-TE with Reduced Label Stack
  • Express segments allow operators to present an abstraction of the network to adjacent domains and/or higher layer systems.

    To establish a traffic engineered path through a series of interconnected domains or multi-domain network, it is necessary to have a certain amount of traffic engineering information about each network domain. Topology abstraction allows the use of policies to connect across domains. Topology abstraction does not necessarily offer all possible connectivity options but presents a view of potential connectivity according to the policies that determine how the domain resources need to be used. The domain could be constructed as a mesh of border node to border node express segments.

    Using Figure 2, PE2’s view of an end-to-end traffic engineered system is represented in its local traffic engineering database as shown in Figure 3.

    Figure 3: Abstracted Traffic Engineered DomainAbstracted Traffic Engineered Domain

Use Cases

This section describes a few use cases for establishing end-to-end SR-TE connectivity. RFC7926 introduces a comprehensive set of terminology and use cases along with an architecture to facilitate traffic engineering link and node information exchange between domains. As Service providers' networks are expanding because of continued growth, multi-domain networks are becoming more prevalent. In these multi-domain networks, it is required to establish an end-to-end traffic engineered path between one or more domains from a source to a destination

Intra and Inter-domain SR-TE Connectivity Using Express Segments

Express segments have the capability to abstract traffic engineering information when the routing information exchange happens between domains. The traffic engineering information used as a criterion for path selection is the data relating to traffic engineered nodes and links. Traffic engineering information may be link metrics such as IGP, traffic engineering, latency, or administrative link attributes such as affinities. Express segments are best described as virtual traffic engineered Links that facilitate the abstraction of underlay LSPs.

Enhanced On-demand Next-hop

Enhanced On-demand Next-hop (EODN) (also known as BGP-triggered SR policies) facilitates the dynamic provisioning of end-to-end SR-TE policies, with constraints, upon the arrival of services routes. In large networks having hundreds of PE devices creating and maintaining traffic engineering policies on any ingress PE for every egress PE is challenging. Considering colors specific services (per VPN or per group of prefixes) makes things even more complicated and harder to maintain and troubleshoot. BGP triggered SR-TE addresses the task by automatically creating dynamic SR tunnels based on pre-configured templates. There is no need to provision ingress PEs with configuration for every egress PE.

How does Express Segment Work?

Express segments can be used to establish end-to-end traffic engineered paths between interconnected traffic engineered networks. Express segments (also known as virtual traffic engineering links) are generated dynamically through policies matching the underlay LSPs. Express segments and the corresponding abstracted topology (required by RFC7926) is generated with policies.

To apply a policy, include the policy policy-name configuration statement at the [edit protocols express-segment traffic-engineering] hierarchy level.

Note:

The policy-name is optional. If a policy name is not defined, then the policy implicitly imports all the express segments into the local traffic engineering database. An express segment template automatically creates a one-on-one mapping of express links.

To configure express segment, include the express-segment configuration statement under the [edit protocols] hierarchy level.

Let us refer to Figure 1 and use the pair of RSVP-TE LSPs shown between C1 and C4 border nodes and how express segments are generated representing the underlay LSPs. In Figure 4, a policy is created to represent two RSVP-TE (gold and liquid-gold) LSPs as a single express segment.

Figure 4: A Pair of RSVP-TE LSPs Represented as an Express SegmentA Pair of RSVP-TE LSPs Represented as an Express Segment

The following is a sample policy where the policy name is matched through a regular expression and the end-point of the RSVP-TE LSPs:

In the following sample output, you can see the newly created express segment (Gold-Exp-Set-192.168.1.4)along with the traffic engineering attributes are inherited from the underlay RSVP-TE tunnels:

You can observe the following in the output:

  • Automatic naming of the express segment (Gold-Exp-Set-192.168.1.4).

  • Traffic engineering attributes (bandwidth, metrics, admin groups, SRLGs) of the underlay RSVP-LSPs are inherited by the express segment.

  • The express segment is an unnumbered traffic engineered link and has been added to the traffic engineering database.

  • Label 19 has been assigned and installed in the mpls.0 forwarding table as the adjacency SID for the SR virtual traffic engineering link.

How are Express Segments Advertised?

Express segments are advertised across domain boundaries or to higher-level controllers and Path Computing Elements (PCEs) using the BGP link state. When exchanging information through the BGP link state, the extensions for the BGP link state are used to advertise express segments as traffic engineered links. The express segment traffic engineered links and other normal traffic engineering links appear in the traffic engineering link-state database of any LSR in the network and are used for computing end-to-end traffic engineered paths. Express segment traffic engineering database entries are imported and exported from the lsdist.0 table (see, Link-State Distribution Using BGP Overview) for advertisement through the BGP link state with the following traffic-engineering database import and export configuration:

Figure 5 provides a visual representation of how traffic engineering links and nodes are mirrored between the local traffic engineering database and the lsdist.0 RIB that BGP-LS uses for advertisement. As illustrated, there are several policy attachment points.

Figure 5: Advertising Express SegmentsAdvertising Express Segments

How are Express Segments Used by a Path Computing Element?

The BGP link state export policy is an effective place to create an abstract or customized topology that is advertised to a traffic engineered peer. For example, you may want to advertise only the express segment and Domain 3’s TE links and nodes to PE2 such that the traffic engineered topology is abstracted as shown in Figure 6. The abstracted view is then used by PE2 for end-to-end path computation.

Figure 6: Abstracting Traffic Engineered Domain 2 with Express SegmentAbstracting Traffic Engineered Domain 2 with Express Segment

The following is a sample configuration of a BGP link state export policy on C1:

The following is a sample SR policy configuration on PE2 router to establish an end-to-end multi-domain path from PE2 to PE3:

The resulting end-to-end path is represented in Figure 7. You can see the express segment’s adjacency SID (label 19) is used in the SR segment-list resulting in traffic being load-balanced over both the gold and liquid-gold RSVP-TE LSPs within Domain 2.

Figure 7: Multi-domain End-to-End SR-TE LSPMulti-domain End-to-End SR-TE LSP

Example: Inter-domain SR-TE Connectivity Using Express Segments

Use this example to learn how to establish an end-to-end inter-domain SR-TE connectivity using express segments.

Requirements

This example uses the following hardware and software components:

  • MX Series routers as provider edge, border nodes, and intermediate routers.

  • Junos OS Release 20.4R1 or later running on all devices.

Overview

The following topology (Figure 8) shows two SR-TE domains (AS100 and AS300) running EBGP-LS inter-connected through an RSVP-TE (AS200) domain:

Topology

Figure 8: Inter-domain SR-TE Connectivity Using Express Segments Inter-domain SR-TE Connectivity Using Express Segments

In this topology, an end-to-end SR-TE path between PE1 router to PE2 router is established. Egress peer engineering (EPE) segments are defined on PE1 and PE2 routers to steer traffic towards their directly connected border nodes BN1/BN2 and BN3/BN4, respectively. EPE segments defined on the border nodes are advertised internally through the BGP link state. These two SR-TE domains are interconnected through the domain (AS200) that is leveraging RSVP-TE LSPs for internal path establishment.

The border nodes of the AS200 domain facilitate the abstraction of SR-TE information between domains. Express segments are created on border nodes (BN1, BN2, BN3, and BN4). Express segments are created in a one-on-one relationship with the underlying RSVP-TE LSPs and all express segments are inserted into the border node's local TE database for subsequent BGP link-state advertisement. The AS200 domain leverages RSVP-TE LSP underlays for TE management and presents those underlay RSVP-TE LSPs as express segments to the AS100 and the AS300 domains, enabling the domains to have end-to-end SR-TE LSP connectivity.

The following table describes the domains, routers, and connections in the topology:

Table 1: Describes the domains, routers, and connections in the Topology

Domain

Devices

Router ID/Lo) Address

Connection Details

AS100

(EBGP-LS/ SR-TE LSP)

R0

(PE1 router)

100.100.100.100

100.100.100.101

Connected to R1 (BN1 router) through interface ge-0/0/0, assigned IP address 192.168.1.1/24.

Connected to R4 (BN2 router) through interface ge-0/0/2, assigned IP address 192.168.2.1/24.

AS200

(RSVP-TE LSP)

R1

(BN1 router)

1.1.1.1

Connected to R0 (PE1 router) through interface ge-0/0/0, assigned IP address 192.168.1.2/24.

Connected to R4 (BN2 router) through interface ge-0/0/3, assigned IP address 192.168.4.1/24.

Connected to R2 (Intermediate router) through interface ge-0/0/2, assigned IP address 192.168.3.1/24.

Connected to R5 (Intermediate router) through interface ge-0/0/4, assigned IP address 192.168.5.1/24.

R4(BN2 router)

4.4.4.4

Connected to R0 (PE1 router) through interface ge-0/0/0, assigned IP address 192.168.2.2/24.

Connected to R1 (BN1 router) through interface ge-0/0/2, assigned IP address 192.168.4.2/24.

Connected to R2 (Intermediate router) through interface ge-0/0/3, assigned IP address 192.168.7.1/24.

Connected to R5 (Intermediate router) through interface ge-0/0/4, assigned IP address 192.168.13.1/24.

R2(Intermediate router)

2.2.2.2

Connected to R1 (BN1 router) through interface ge-0/0/0, assigned IP address 192.168.3.2/24.

Connected to R4 (BN2 router) through interface ge-0/0/2, assigned IP address 192.168.7.1/24.

Connected to R5 (Intermediate router) through interface ge-0/0/3, assigned IP address 192.168.8.1/24.

Connected to R3 (BN3 router) through interface ge-0/0/1, assigned IP address 192.168.6.1/24.

Connected to R6 (BN4 router) through interface ge-0/0/4, assigned IP address 192.168.9.1/24.

R5

(Intermediate router)

5.5.5.5

Connected to R1 (BN1 router) through interface ge-0/0/0, assigned IP address 192.168.5.2/24.

Connected to R4 (BN2 router) through interface ge-0/0/3, assigned IP address 192.168.13.2/24.

Connected to R2 (Intermediate router) through interface ge-0/0/1, assigned IP address 192.168.8.2/24.

Connected to R3 (BN3 router) through interface ge-0/0/2, assigned IP address 192.168.10.2/24.

Connected to R6 (BN4 router) through interface ge-0/0/4, assigned IP address 192.168.14.1/24.

R3

(BN3 router)

3.3.3.3

Connected to R7 (PE2 router) through interface ge-0/0/3, assigned IP address 192.168.12.1/24.

Connected to R6 (BN4 router) through interface ge-0/0/2, assigned IP address 192.168.11.1/24.

Connected to R2 (Intermediate router) through interface ge-0/0/0, assigned IP address 192.168.6.2/24.

Connected to R5 (Intermediate router) through interface ge-0/0/1, assigned IP address 192.168.10.1/24.

R6

(BN4 router)

6.6.6.6

Connected to R7 (PE2 router) through interface ge-0/0/3, assigned IP address 192.168.15.1/24.

Connected to R3 (BN3 router) through interface ge-0/0/1, assigned IP address 192.168.11.2/24.

Connected to R2 (Intermediate router) through interface ge-0/0/0, assigned IP address 192.168.9.2/24.

Connected to R5 (Intermediate router) through interface ge-0/0/2, assigned IP address 192.168.14.2/24.

AS300

(EBGP-LS/SR-TE LSP)

R7

(PE2 router)

7.7.7.7

Connected to R3 (BN3 router) through interface ge-0/0/0, assigned IP address 192.168.12.2/24.

Connected to R6 (BN4 router) through interface ge-0/0/1, assigned IP address 192.168.15.2/24.

Configuration

To inter-connect a multi-domain network and establish an end-to-end SR path using express segments, perform these tasks:

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode.

Device R0 (PE1 router)

Device R1 (BN1 router)

Device R4 (BN2 router)

Device R2 (Intermediate router)

Device R5 (Intermediate router)

Device R3 (BN3 router)

Device R6 (BN4 router)

Device R7 (PE2 router)

Configure R0 (PE1 router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R0:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure BGP to enable BGP-LS route advertisement to the connected peers and define the EPE links. Since express segment is an internal TE link, this configuration creates an external TE link.

  7. Enable import and export of traffic engineering database parameters using policies.

  8. Configure MPLS administrative group policies for LSP path computation.

  9. Configure the MPLS label range to assign static labels for the EPE links.

  10. Configure MPLS on the interfaces.

  11. Configure SR-TE policies on the ingress router to enable end-to-end SR-TE policy.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-optionsshow routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configure R1 (BN1 router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R1:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure BGP to enable BGP-LS route advertisement to the connected peers and define the EPE links. Since express segment is an internal TE link, this configuration creates an external TE link.

  7. Configure the express segment set and express segment templates. What the express segment template does is it manually assigns or overrides inherited attributes to the express segments regardless of what the underlay attributes are. The express segment name r1-exp-set1 is prefixed to the underlay end point for automatic naming.

  8. Configure IS-IS protocol on the interfaces and apply MPLS administrative groups to those interfaces.

  9. Enable link protection on all the RSVP interfaces. Using link protection, you can configure a network to reroute traffic quickly around broken links.

  10. Enable import and export of traffic engineering database parameters using the policies.

  11. Configure MPLS administrative group policies for LSP path computation.

  12. Configure MPLS with a label-switched path (LSP) and include administrative groups.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-options, show routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configure R4 (BN2 router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R4:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure the express segment set and express segment templates. What the express segment template does is it manually assigns or overrides inherited attributes to the express segments regardless of what the underlay attributes are. The express segment name r4-exp-set1 is prefixed to the underlay end point for automatic naming.

  7. Configure IS-IS and MPLS protocol on the interfaces.

  8. Enable import and export of traffic engineering database parameters using policies.

  9. Configure MPLS administrative group policies for LSP path computation.

  10. Configure MPLS with a label-switched path (LSP) and include administrative groups.

  11. Configure the MPLS label range to assign static labels for the EPE links.

  12. Enable link protection on all the RSVP interfaces. Using link protection, you can configure a network to reroute traffic quickly around broken links.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-options, show routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configure R2 (Intermediate router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R2:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure BGP to enable BGP-LS route advertisement to the connected peers.

  7. Configure IS-IS and MPLS protocol on the interfaces.

  8. Configure MPLS administrative group policies for LSP path computation.

  9. Configure the MPLS label range to assign static labels for the EPE links.

  10. Enable link protection on all the RSVP interfaces. Using link protection, you can configure a network to reroute traffic quickly around broken links.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-options, show routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configure R5 (Intermediate router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R5:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure IS-IS and MPLS protocol on the interfaces.

  7. Configure BGP to enable BGP-LS route advertisement to the connected peers.

  8. Configure MPLS administrative group policies for LSP path computation.

  9. Configure the MPLS label range to assign static labels for the EPE links.

  10. Enable link protection on all the RSVP interfaces. Using link protection, you can configure a network to reroute traffic quickly around broken links.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-options, show routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configure R3 (BN3 router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R3:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure BGP to enable BGP-LS route advertisement for peer and define the EPE links. Since express segment is an internal TE link, this configuration creates an external TE link.

  7. Define a mechanism to automatically (dynamic) create express segments and insert them in to the TE database so that they can be advertised through BGP-LS. In this example, express segments are created for all the underlay RSVP tunnels automatically. This is done by configuring a template with a policy and then express segments are automatically created based on the policies.

  8. Configure IS-IS and MPLS protocol on the interfaces.

  9. Enable import and export of traffic engineering database parameters using policies.

  10. Configure MPLS administrative group policies for LSP path computation.

  11. Configure MPLS with a label-switched path (LSP) and include administrative groups.

  12. Configure the MPLS label range to assign static labels for the EPE links.

  13. Enable link protection on all the RSVP interfaces. Using link protection, you can configure a network to reroute traffic quickly around broken links.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-options, show routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configure R6 (BN4 router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R6:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure BGP to enable BGP-LS route advertisement for peer and define the EPE links. Since express segment is an internal TE link, this configuration creates an external TE link.

  7. Define a mechanism to automatically (dynamic) create express segments and insert them in to the TE database so that they can be advertised through BGP-LS. In this example, express segments are created for all the underlay RSVP tunnels automatically. This is done by configuring a template with a policy and then express segments are automatically created based on the policies.

  8. Configure IS-IS and MPLS protocol on the interfaces.

  9. Enable import and export of traffic engineering database parameters using policies.

  10. Configure MPLS administrative group policies for LSP path computation.

  11. Configure MPLS with a label-switched path (LSP) and include administrative groups.

  12. Configure the MPLS label range to assign static labels for the EPE links.

  13. Enable link protection on all the RSVP interfaces. Using link protection, you can configure a network to reroute traffic quickly around broken links.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-options, show routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configure R7 (PE2 router)

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure device R7:

  1. Configure the network services mode as Enhanced IP. Enhanced IP sets the router's network services to enhanced Internet Protocol and uses enhanced mode capabilities.

    After you configure the enhanced-ip statement and commit the configuration, the following warning message appears prompting you to reboot the router:

    The reboot brings up the FPCs on the router.

  2. Configure the interfaces to enable IP, MPLS, and ISO transport.

  3. Configure the loopback interface to enable tunnel endpoints and service endpoints.

  4. Configure routing options to identify the router in the domain.

  5. Define import and export policies. For example, configure policies that export EPE TE links from the local TE database to lsdist.0 and policies to import from lsdist.0 into the local TE database. You can configure policies to advertise the BGP routes to a peer.

  6. Configure BGP to enable BGP-LS route advertisement for peer and define the EPE links. Since express segment is an internal TE link, this configuration creates an external TE link.

  7. Configure MPLS protocol on the interfaces.

  8. Enable import and export of traffic engineering database parameters using policies.

  9. Configure MPLS administrative group policies for LSP path computation.

  10. Configure the MPLS label range to assign static labels for the EPE links.

  11. Configure SR-TE policies on the ingress router to enable end-to-end SR-TE policy.

Results

From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show policy-options, show routing-options, and show protocols commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Verification

To confirm that the configuration is working properly, perform the following tasks:

Verify the Express Segment

Purpose

Verify that the express segments are created correctly.

Action

From operational mode, run the following commands:

  • show express-segments detail—Verify whether the express segments are created.

  • show ted database topology-type express-segments detail—Verify that the newly created express segments are inserted into the TE database.

  • show route table mpls.0 protocol express-segments—Verify whether the forwarding entries have been created.

On R1

On R1

Meaning
  • In the show express-segments detail output, you can see the name of the express segments (r1-exp-set1-6.6.6.6, r1-exp-set2-3.3.3.3), express segment labels (25, 24), and the underlay LSPs (lsp1to6_a, lsp1to3_a).

  • In the show ted database topology-type express-segments detail output, you can see the express segment entries are inserted into the TE database. The express segments (virtual TE links) are dynamically created. The protocol used is EXPRESS-SEG(0).

  • In the show route table mpls.0 protocol express-segments output, you can see the express segment labels (24,25). Because the express segment is a construct that relies on the underlay LSPs, the express segment label gets swapped to the underlay LSP labels (33,34), which is RSVP-LSP.

Verify the Express Segment Advertisements

Purpose

Verify that the originating node advertises express segments to its eBGP/iBGP LS neighbors.

Action

From operational mode, run the following commands:

  • show route table lsdist.0—Verify that the express segments in the RIB BGP-LS are being advertised.

  • show route advertising-protocol bgp neighbor—Verify that the express segments are sent to the eBGP/iBGP LS neighbors.

On R1

Meaning
  • In the show route table lsdist.0 output, BGP advertises the routes in the routing table. The routing table is created from the TE database. You can see the express segments (EXPRESS-SEG/6) links and the EPE links (BGP-LS-EPE:0 }/1216).

  • In the show route advertising-protocol bgp 2.2.2.2 output, you can see what R1 is advertising to. The express segments are inserted into the TE database, which is copied to RIB. BGP-LS advertises the RIB to the peer router. On the peer, the received RIB information is copied into the local database. The policy in this example only advertises express segments and EPE segments.

Verify the TE Topology Information

Purpose

Verify that the ingress nodes receive TE topology information through eBGP/iBGP LS.

Action

From operational mode, run the following commands:

  • show route receive-protocol bgp neighbor—Verify that the express segments are received from eBGP/iBGP LS neighbors.

  • show route table lsdist.0—Verify that the express segments are in the BGP-LS RIB.

  • show ted database topology-type l3-unicast detail—Verify that the express segments are imported into the ingress router’s TE database.

  • show spring-traffic-engineering lsp—Verify that the end-to-end SR policy has been successfully computed and installed.

On R0

On R0

On R0

On R0

On R0

Meaning
  • In the show route receive-protocol bgp 1.1.1.1 output, it shows the routes that have been received by the ingress router (R0) from the BGP neighbor, which describes the express segment (virtual TE links).

  • In the show route table lsdist.0 output, it shows the routes that have been received by the ingress router (R0) and whether they are inserted into the lsdist.0 RIB. It also shows whether the lsdist.0 RIB is copied into the local TE database.

  • In the show ted database topology-type l3-unicast detail output, the routes are copied into the local TE database. The r1-exp-set1-6.6.6.6 is an express segment with end point as 6.6.6.6 and is sucessfully created on R1. R1 has advertised the express segment and R0 has inserted it into the local TE database. You can also see the EPE segments (epe_adj1_toR7).

  • In the show spring-traffic-engineering lsp output, you can see that the SR policies are up. It shows that you are now able to compute a multi-domain end-to-end (R0 to R7) SR policy.

  • In the show spring-traffic-engineering lsp detail output, you can see the labels that are selected. In the computelsp1 LSP, the label 7104 is an EPE segment, 21 is the express segment, and 7167 is also an EPE segment. It shows that you are now able to compute a multi-domain end-to-end (R0 to R7) SR policy.