Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

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 1) shows two SR-TE domains (AS100 and AS300) running EBGP-LS inter-connected through an RSVP-TE (AS200) domain:

Topology

Figure 1: 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

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.

user@R1>show express-segments detail

On R1

user@R1>show ted database topology-type express-segments detail

On R1

user@R1>show route table mpls.0 protocol express-segments

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.

user@R1>show route table lsdist.0

On R1

user@R1>show route advertising-protocol bgp 2.2.2.2

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

user@R0>show route receive-protocol bgp 1.1.1.1

On R0

user@R0>show route table lsdist.0

On R0

user@R0>show ted database topology-type l3-unicast detail

On R0

user@R0>show spring-traffic-engineering lsp

On R0

user@R0>show spring-traffic-engineering lsp detail

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.