Configuring EVPN VPLS over SRv6 Flex-Algo

This section describes how to configure EVPN VPLS over SRv6 Flex-Algo.

Usage Scenario

EVPN VPLS uses the EVPN E-LAN model to carry MP2MP VPLS services.

EVPN VPLS over SRv6 Flex-Algo uses forwarding paths calculated based on Flex-Algos to carry EVPN E-LAN services on the public network.

On the network shown in Figure 1, multiple links exist between PEs. You can configure the PEs to forward EVPN E-LAN services over a path calculated using a specified Flex-Algo.

Figure 1 EVPN VPLS over SRv6 Flex-Algo networking

Pre-configuration Tasks

Before performing the configuration, complete the following tasks:

Configure IS-IS to enable devices to communicate at the network layer.
Enable the advertisement of IPv6 delay information if the Flex-Algo metric type is delay.

Procedure

Configure Flex-Algo link attributes.
1. Run system-view
  The system view is displayed.
2. Run te attribute enable
  TE is enabled.
3. Run path-constraint affinity-mapping
  An affinity name template is configured, and the template view is displayed.
  
  This template must be configured on each node that is involved in path calculation, and the same mappings between affinity bit names and values must be configured on each node.
4. Run attribute bit-name bit-sequence bit-number
  Mappings between affinity bit values and names are configured.
  
  An affinity attribute has a total of 128 bits. This step configures only one bit. Repeat this step to configure more bits. You can configure some or all of the bits in the affinity attribute.
5. Run quit
  Return to the system view.
6. Use either of the following methods to configure Flex-Algo link attributes.
  - Inherit interface TE attributes.
    1. Run interface interface-type interface-number
      The interface view is displayed.
    2. Run te link administrative group name bit-name &<1-32>
      The link administrative group attribute is configured. The bit-name value must be in the range specified in the affinity name template.
    3. Run te metric metric-value
      The TE metric of the link is configured.
    4. Run te link-attribute-application flex-algo
      The Flex-Algo link attribute application view is created and displayed.
    5. Run te inherit
      The interface TE attributes are inherited.
      
      After the te inherit command is run, the Flex-Algo link inherits the te metric and te link administrative group name command configurations on the interface.
      
      In the Flex-Algo link attribute application view, the te inherit command is mutually exclusive from the metric and link administrative group name commands.
  - Configure Flex-Algo link attributes separately.
    1. Run interface interface-type interface-number
      The interface view is displayed.
    2. Run te link-attribute-application flex-algo
      The Flex-Algo link attribute application view is created and displayed.
    3. Run link administrative group name name-string &<1-128>
      The link administrative group attribute of the Flex-Algo link is configured. The name-string value must be in the range specified in the affinity name template.
    4. (Optional) Run delay delay-value
      The Flex-Algo link delay is configured.
    5. (Optional) Run metric metric-value
      The Flex-Algo link metric is configured.
7. Run quit
  Return to the interface view.
8. Run quit
  Return to the system view.
Configure a FAD.
1. Run flex-algo identifier flexAlgoId
  A Flex-Algo is created, and the Flex-Algo view is displayed.
2. Run priority priority-value
  The priority of the Flex-Algo is configured.
  
  A larger value indicates a higher priority.
3. Run metric-type { igp | delay | te }
  The Metric-Type of the Flex-Algo is configured.
  
  After this command is run, links must have the corresponding metric type. Otherwise, these links will be pruned and cannot participate in IGP path calculation.
4. Run affinity { include-all | include-any | exclude } { name-string } &<1-32>
  The affinity attribute of the Flex-Algo is configured.
  
  A FAD can constrain a path to include or exclude a link with a specific affinity attribute. The following three types of affinity attributes are defined for FADs:
  - Include-All Admin Group (include-all): A link is included in path calculation only if each link administrative group bit has the same name as each affinity bit.
  - Include-Any Admin Group (include-any): A link is included in path calculation if at least one link administrative group bit has the same name as an affinity bit.
  - Exclude Admin Group (exclude): A link is excluded from path calculation if any link administrative group bit has the same name as an affinity bit.
5. Run quit
  Exit the Flex-Algo view.
Configure IPv6 IS-IS on each PE and P. For configuration details, see Configuring Basic IPv6 IS-IS Functions.
Configure BD-EVPN functions on PEs.
Establish a BGP EVPN peer relationship between PEs.
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. (Optional) Run router-id ipv4-address
  A BGP router ID is configured.
4. Run peer ipv6-address as-number { as-number-plain | as-number-dot }
  The remote PE is configured as a peer.
5. Run peer ipv6-address connect-interface loopback interface-number
  The interface on which a TCP connection to the specified BGP peer is established is specified.
6. Run l2vpn-family evpn
  The BGP EVPN address family view is displayed.
7. Run peer ipv6-address enable
  The device is enabled to exchange EVPN routes with the specified peer.
8. Run peer { ipv6-address | group-name } advertise encap-type srv6 [ advertise-srv6-locator ]
  The device is enabled to send EVPN routes carrying SRv6-encapsulated attributes to the specified peer or peer group.
  
  In a scenario where BFD is used to check locator reachability, after locator routes are summarized by a P device between local and remote PEs, the remote PE can learn only the summary locator route, not the locator on the local PE. This leads to a BFD failure. To address this issue, configure the advertise-srv6-locator parameter in the command to allow the local PE to carry locator length information in the EVPN route advertised to the remote PE. In this way, after receiving the EVPN route, the remote PE can calculate the locator on the local PE, enabling BFD to take effect.
9. Run quit
  Exit the BGP EVPN address family view.
10. Run quit
  Exit the BGP view.
11. Run commit
  The configuration is committed.
Configure basic SRv6 functions.
1. (Optional) Run evpn srv6 next-header-field { 59 | 143 }
  A value is set for the Next Header field in an SRv6 extension header.
  
  If the value is 59 in earlier versions, you can perform this step to change the value to 59 to ensure compatibility with the earlier versions.
2. Run segment-routing ipv6
  SRv6 is enabled, and the SRv6 view is displayed.
3. Run encapsulation source-address ipv6-address [ ip-ttl ttl-value ]
  A source address is specified for SRv6 EVPN encapsulation.
4. Run locator locator-name ipv6-prefix ipv6-address prefix-length [ static static-length | args args-length | flex-algo flexAlgoId ] ^*
  An SRv6 locator is configured.
  
  If flex-algo flexAlgoId is specified, the IGP uses the specified Flex-Algo to calculate locator routes.
  
  In SRv6 Flex-Algo scenarios, locators must be configured on both PEs and Ps, and IS-IS SRv6 must be enabled using the segment-routing ipv6 locator locator-name command in the IS-IS view. Otherwise, SRv6 locator routes cannot be advertised, and PEs at both ends cannot learn locator routes from each other.
5. (Optional) Run opcode func-opcode end-dt2m bridge-domain bd-id
  A static End.DT2M SID operation code (opcode) is configured.
  
  Perform this step if a static locator is configured using the static static-length parameter. End.DT2M SIDs are used for BUM traffic forwarding through VPLS.
6. (Optional) Run opcode func-opcode { end-dt2u | end-dt2ul } bridge-domain bd-id
  Static End.DT2U and End.DT2UL SID opcodes are configured.
  
  Perform this step if a static locator is configured using the static static-length parameter. End.DT2U SIDs are used for the forwarding of known unicast traffic through VPLS. In dual-homing scenarios, an End.DT2UL SID opcode needs to be specified for the bypass path to prevent traffic loops between PEs.
7. Run quit
  Exit the SRv6 locator view.
8. Run quit
  Exit the SRv6 view.
Enable IS-IS SRv6 on the PEs and Ps.
1. Run isis [ process-id ]
  The IS-IS view is displayed.
2. Run cost-style { wide | compatible | wide-compatible }
  The wide cost type is configured.
3. Run flex-algo flexAlgoIdentifier [ level-1 | level-2 | level-1-2 ]
  IS-IS is enabled to advertise Flex-Algos.
4. Run ipv6 enable topology ipv6
  IPv6 is enabled for the IS-IS process in the IPv6 topology.
5. Run ipv6 traffic-eng [ level-1 | level-2 | level-1-2 ]
  IS-IS TE is enabled.
6. (Optional) Run ipv6 metric-delay advertisement enable { level-1 | level-2 | level-1-2 }
  The advertisement of IPv6 delay information is enabled.
  
  In a scenario where IS-IS Flex-Algos calculate paths based on delay information, you need to run this command to enable link delay advertisement through IS-IS.
7. Run segment-routing ipv6 locator locator-name [ auto-sid-disable ]
  IS-IS SRv6 is enabled.
  
  In this command, the value of locator-name must be the same as that configured using the locator locator-name ipv6-prefix ipv6-address prefix-length [ static static-length | args args-length | flex-algo flexAlgoId ] ^* command. If a separate locator is configured for each of BUM traffic and known unicast traffic of EVPN VPLS services, you need to run this command once for each locator so that IS-IS advertises them both.
8. Run quit
  Exit the IS-IS view.
Configure EVPN routes to carry SIDs and recurse to SRv6 BE paths based on the SIDs.
1. Run evpn vpn-instance vpn-instance-name bd-mode
  The view of the EVPN instance that works in BD mode is displayed.
2. Run segment-routing ipv6 locator locator-name [ unicast-locator unicast-locator-name ]
  The device is enabled to carry SIDs in EVPN routes to be advertised.
  For the preceding command:
  - locator-name must be set to an End.DT2M SID, with the args parameter specified. unicast-locator-name must be set to an End.DT2U or End.DT2UL SID, with the args parameter not specified. If the locator-name and unicast-locator-name parameters are both required, you need to run the locator locator-name ipv6-prefix ipv6-address prefix-length [ static static-length | args args-length | flex-algo flexAlgoId ] ^* command to create two corresponding locators before setting the two parameters.
  - In EVPN VPLS dual-homing scenarios, the args parameter is used to stitch ESI labels for End.DT2M SIDs only. This results in a waste of End.DT2U SIDs. To conserve SIDs, you can separately configure a locator for End.DT2U SIDs and a locator for End.DT2M SIDs. The former locator does not require the args parameter to be specified. You can then bind the two locators to the same EVPN instance.
  - If static SIDs are configured in the locator named using locator-name or unicast-locator-name, use static SIDs. Otherwise, use dynamically allocated SIDs.
3. Run segment-routing ipv6 best-effort
  The device is enabled to perform route recursion to SRv6 BE paths based on the SIDs carried by routes.
4. Run commit
  The configuration is committed.

Verifying the Configuration

After configuring EVPN VPLS over SRv6 Flex-Algo, verify the configuration.

Run the display segment-routing ipv6 local-sid { end-dt2u | end-dt2ul | end-dt2m } [ sid ] [ bridge-domain bd-id ] forwarding command to check information about the SRv6 BE local SID table.

Run the display bgp evpn { all | route-distinguisher route-distinguisher | vpn-instance vpn-instance-name } routing-table [ { ad-route | es-route | inclusive-route | mac-route | prefix-route } prefix ] command to check BGP EVPN route information.
Run the display isis process-id flex-algo [ flex-algo-id ] [ level-1 | level-2 ] command to check the preferred FAD in the LSDB.
Run the display isis lsdb [ { level-1 | level-2 } | verbose | { local | lsp-id | is-name symbolic-name } ] ^* [ process-id | vpn-instance vpn-instance-name ] command to check IS-IS LSDB information.
Run the display isis process-id route ipv6 flex-algo [ flex-algo-id ] [ verbose | [ level-1 | level-2 ] | ipv6-address [ prefix-length ] ] ^* or display isis route [ process-id ] ipv6 flex-algo [ flex-algo-id ] [ verbose | [ level-1 | level-2 ] | ipv6-address [ prefix-length ] ] ^* command to check Flex-Algo-related IS-IS route information.
Run the display isis [ process-id ] spf-tree [ systemid systemid ] ipv6 flex-algo [ flex-algo-id ] [ [ level-1 | level-2 ] | verbose ] ^* command to check the SPF tree topology information of a specified Flex-Algo.