Configure EVPN Service over SRTE
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Contents
Introduction
This document describes how to configure Ethernet Virtual Private Network (EVPN) services over Segment Routing Traffic Engineering (SRTE).
Prerequisites
Requirements
Cisco recommends that you have basic knowledge of:
- Intermediate System-to-Intermediate System (ISIS)
- SRTE
- EVPN
Components Used
The information in this document is based on Device: Aggregation Services Router 9000 (ASR9K).
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.
Network Topology
Figure 1. Network Topology Diagram
Note: To establish inter-domain SRTE policy, you need to use PCE to have visibility of all the nodes in multiple domains.
Segment-Routing Traffic Engineering Overview
SRTE Policy
An SR Policy is identified through the parameters:
- The head end where the policy is instantiated/implemented
- The endpoint (that is the destination of the policy)
- The color (an arbitrary numerical value)
SR-TE Database
SRTE Database is a key component in the Segment Routing (SR) architecture, it is used to store:
- The SID values of the node and network segments.
- Details about the network topology, including available links, metrics, and constraints like bandwidth or latency.
- It is used by routers to determine the best paths for forwarding packets based on predefined constraints or optimization goals specified in the SR policy.
IGP path taken from PE1 to PE3 without SRTE policy configuration:
RP/0/RSP1/CPU0:ASR9906-1-PE1#traceroute mpls ipv4 10.10.33.33/32 source 10.10.11.11
Type escape sequence to abort.
0 10.10.111.11 MRU 1500 [Labels: 16033 Exp: 0]
L 1 10.10.111.1 MRU 1500 [Labels: explicit-null Exp: 0] 7 ms >>>>>>>>>>>>>>>>> P1
! 2 10.10.133.33 4 ms>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> PE3
Figure 2 IGP path taken from PE1 to PE3
Configuration to Populate the SRTE Database
router isis core1
is-type level-2-only
net 49.0005.0000.1010.0505.00
distribute link-state
address-family ipv4 unicast
Note:
- Distribute link-state is required for populating the SRTE database.
- when this command is not configured the SRTE database would be empty .
Verification
RP/0/RSP0/CPU0:ASR9906-2-ABR #show segment-routing traffic-eng ipv4 topology
SR-TE topology database
-----------------------
Node 2
TE router ID: 10.10.1.1
Host name: ASR9910-4-P1
ISIS system ID: 0000.1010.0101 level-2
Prefix SID:
Prefix 10.10.1.1, label 16001 (regular), flags: X:0, R:0, N:1, P:1, E:1, V:0, L:0, M:0 >>>>> node details
Link[0]: local address 10.10.15.1, remote address 10.10.15.5
Local node:
ISIS system ID: 0000.1010.0101 level-2
Remote node:
TE router ID: 10.10.5.5
Host name: ASR9906-2-ABR
ISIS system ID: 0000.1010.0505 level-2
Metric: IGP 10, TE 10, Latency 10 microseconds >>>>>>>>> metric and latency of this link between P1 and ABR
Bandwidth: Total link 12499999744, Reservable 0 >>>>>>> BW of this link
Admin-groups: 0x00000000
Admin-groups-detail:
Adj SID: 24005 (protected) 24006 (unprotected) >>>>>>>> adj sid of link on P1
Static SRTE Policy
Configuration
Configure the SRTE Static policy on the Head end router PE1:
segment-routing
traffic-eng
segment-list STATIC-SID-LIST
index 1 mpls label 16055 >>>>>>> node SID of ABR
index 2 mpls label 16022 >>>>>>> node SID of PE2
index 3 mpls label 16033 >>>>>>> node SID of PE3
!
policy Static-policy-evpnvpws
binding-sid mpls 3000
color 10 end-point ipv4 10.10.33.33
candidate-paths
preference 5
explicit segment-list STATIC-SID-LIST
Note:
- Manually configured Binding SID 3000
- Color is 10 and the end point PE3
- This SR TE policy is using the explicit SID list to steer the traffic in a predefined path
RP/0/RSP1/CPU0:ASR9906-1-PE1#traceroute sr-mpls policy binding-sid 3000 lsp-end-point 10.10.33.33 source 10.10.11.11 verbose
Type escape sequence to abort.
0 10.10.115.11 10.10.115.5 MRU 1500 [Labels: 16022/16033 Exp: 0/0]
L 1 10.10.115.5 10.10.225.22 MRU 1500 [Labels: explicit-null/16033 Exp: 0/0] 6 ms, ret code 8
L 2 10.10.225.22 10.10.123.33 MRU 1500 [Labels: explicit-null Exp: 0] 5 ms, ret code 8
! 3 10.10.123.33 5 ms, ret code 3
Note: The first hop is ABR, which has the node SID 16055; hence it is not appended when the packet is sent out.
Figure 3 Static SRTE policy path taken from PE1 to PE3
Verification
RP/0/RSP1/CPU0:ASR9906-1-PE1#show segment-routing traffic-eng policy color 10
SR-TE policy database
---------------------
Color: 10, End-point: 10.10.33.33
Name: srte_c_10_ep_10.10.33.33
Status:
Admin: up Operational: up for 3d02h (since Jan 14 08:39:30.042)
Candidate-paths:
Preference: 5 (configuration) (active)
Name: Static-policy-evpnvpws
Requested BSID: 3000
Protection Type: protected-preferred
Maximum SID Depth: 10
Explicit: segment-list STATIC-SID-LIST (valid)
Weight: 1, Metric Type: TE
16055 [Prefix-SID, 10.10.25.25]
16022
16033
Attributes:
Binding SID: 3000
Forward Class: Not Configured
Steering labeled-services disabled: no
Steering BGP disabled: no
IPv6 caps enable: yes
Invalidation drop enabled: no
RP/0/RSP1/CPU0:ASR9906-1-PE1#show segment-routing traffic-eng forwarding policy color 10
SR-TE Policy Forwarding database
--------------------------------
Color: 10, End-point: 10.10.33.33
Name: srte_c_10_ep_10.10.33.33
Binding SID: 3000
Active LSP:
Candidate path:
Preference: 5 (configuration)
Name: Static-policy-evpnvpws
Local label: 24012
Segment lists:
SL[0]:
Name: STATIC-SID-LIST
Switched Packets/Bytes: 30/2740
[MPLS -> MPLS]: 30/2740
Paths:
Path[0]:
Outgoing Label: 16022
Outgoing Interfaces: HundredGigE0/1/0/0
Next Hop: 10.10.115.5
Switched Packets/Bytes: 30/2740>>>>>>>>>>> this is the number packet steered using this path
[MPLS -> MPLS]: 30/2740
FRR Pure Backup: No
ECMP/LFA Backup: No
Internal Recursive Label: Unlabelled (recursive)
Label Stack (Top -> Bottom): { 16022, 16033 }
Policy Packets/Bytes Switched: 30/2620>>>>>>>>> this counter shows the packets were transmitted using this policy
RP/0/RSP1/CPU0:ASR9906-1-PE1#show mpls forwarding labels 3000 detail
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
3000 Pop No ID srte_c_10_ep point2point 2620
Version: 69, Priority: 2
Label Stack (Top -> Bottom): { Unlabelled Imp-Null }
NHID: 0x0, Encap-ID: N/A, Path idx: 0, Backup path idx: 0, Weight: 0
MAC/Encaps: 0/0, MTU: 0
Outgoing Interface: srte_c_10_ep_10.10.33.33 (ifhandle 0x020001e0)
Packets Switched: 30
Note: 3000 -Binding sid is used to steer the packets into the SRTE.
RP/0/RSP1/CPU0:ASR9906-1-PE1#show mpls forwarding labels 24012 detail
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
24012 16022 SR TE: 1 [TE-INT] Hu0/1/0/0 10.10.115.5 2740
Version: 68, Priority: 2
Label Stack (Top -> Bottom): { 16022 16033 }
NHID: 0x0, Encap-ID: N/A, Path idx: 0, Backup path idx: 0, Weight: 0
MAC/Encaps: 4/12, MTU: 1500
Outgoing Interface: HundredGigE0/1/0/0 (ifhandle 0x06000480)
Packets Switched: 30
Note: 24012 this is the local label assigned to this policy which is swapped with the outgoing label of the policy.
Associating Static SRTE Policy static-policy-evpnvpws with EVPN VPWS
Configuration
l2vpn
pw-class evpn-srte
encapsulation mpls
preferred-path sr-te policy srte_c_10_ep_10.10.33.33
xconnect group EVPN-vpws
p2p EVPN-vpws-400
interface HundredGigE0/1/0/2.400
neighbor evpn evi 400 target 333 source 111
pw-class evpn-srte
Note: The EVPN routes are not colored, as the SRTE policy is manually associated with the l2vpn and all the traffic via this xconnect takes the SRTE policy path.
Verification
RP/0/RSP1/CPU0:ASR9906-1-PE1#show bgp l2vpn evpn
Route Distinguisher: 10.10.11.11:400 (default for vrf VPWS:400)
*> [1][0000.0000.0000.0000.0000][111]/120
0.0.0.0 0 i
*>i[1][0000.0000.0000.0000.0000][333]/120
10.10.33.33 100 0 i
RP/0/RSP1/CPU0:ASR9906-1-PE1#show l2vpn xconnect
XConnect Segment 1 Segment 2
Group Name ST Description ST Description ST
------------------------ ----------------------------- -----------------------------
EVPN-vpws EVPN-vpws-400
UP Hu0/1/0/2.400 UP EVPN 400,333,10.10.33.33
UP
RP/0/RSP1/CPU0:ASR9906-1-PE1#show l2vpn xconnect group EVPN-vpws xc-name EVPN-vpws-400 detail
Group EVPN-vpws, XC EVPN-vpws-400, state is up; Interworking none
AC: HundredGigE0/1/0/2.400, state is up
Type VLAN; Num Ranges: 1
Rewrite Tags: []
VLAN ranges: [400, 400]
MTU 1500; XC ID 0x1800008; interworking none
Statistics:
packets: received 90, sent 89
bytes: received 7140, sent 7296
drops: illegal VLAN 0, illegal length 0
EVPN: neighbor 10.10.33.33, PW ID: evi 400, ac-id 333, state is up ( established )
XC ID 0xa000000b
Encapsulation MPLS
Encap type Ethernet, control word enabled
Sequencing not set
Preferred path Active : SR TE srte_c_10_ep_10.10.33.33 (BSID:3000, IFH:0x20001e0), Statically configured, fallback enabled
Ignore MTU mismatch: Enabled
Transmit MTU zero: Enabled
Tunnel : Up
EVPN Local Remote
------------ ------------------------------ -----------------------------
Label 24014 24016
MTU 1514 unknown
Control word enabled enabled
AC ID 111 333
EVPN type Ethernet Ethernet
------------ ------------------------------ -----------------------------
Create time: 14/01/2025 08:49:57 (1w1d ago)
Last time status changed: 14/01/2025 11:14:31 (1w0d ago)
Statistics:
packets: received 89, sent 90
bytes: received 7296, sent 7140
RP/0/RSP1/CPU0:ASR9906-1-PE1#show im database ifhandle 0x20001e0
Node 0/RSP1/CPU0 (0x120)
Interface srte_c_10_ep_10.10.33.33, ifh 0x020001e0 (up, 1500)
Interface flags: 0x000000000042c457 (PHYS_ON_RP|REPLICATED
|DYN_REP|TUNNEL|IFINDEX|VIRTUAL|CONFIG|VIS|DATA
|CONTROL)
Encapsulation: mpls_te
Interface type: IFT_TUNNEL_TE
Control parent: None
Data parent: None
Views: UL|GDP|LDP|G3P|L3P|OWN
Protocol Caps (state, mtu)
-------- -----------------
None mpls_te (up, 1500)
ipv4 ipv4 (up, 1500)
mpls mpls (up, 1500)
ipv6 ipv6_preswitch (up, 1500)
ipv6 ipv6 (up, 1500)
On-Demand Nexthop (ODN) SRTE
ODN SRTE policy automates the creation of segment routing traffic engineering paths based on real-time network demand and specified constraints, ensuring dynamic and efficient traffic steering.
These policies are triggered by received routes that share the same color as the ODN policy. The LSP (Label Switched Path) endpoint dynamically associates with the protocol next-hop of these routes.
Configuration
segment-routing
traffic-eng
on-demand color 500
dynamic
metric
type te
Note: this policy comes up only with a valid LSP end point which is Next-Hop of the received routes with the matching color extended community.
Use ODN SRTE Policy for EVPN ELAN Service
As ODN SRTE is a dynamic policy the routes received need to colored 500 cause of this coloring the traffic destined to that route Next-Hop take the ODN SRTE policy path if the route is not colored it takes the IGP path.
Configuration
extcommunity-set opaque color_500
500
end-set
The color is defined in the extended community:
route-policy RPL_color_500
if evpn-route-type is 1 or evpn-route-type is 3 then
set extcommunity color color_500
endif
end-policy
Note:
- evpn-route-type 3 needs to be colored, as it provides the label to carry the BUM traffic, when BUM traffic must be sent to a remote PE3 from PE1to be sent via SRTE policy color 500.
- For unicast traffic, the unicast label for a MAC is advertised by RT-2, but when RT-2 is colored using RPL, an error message is observed:
RP/0/RP0/CPU0:PE2#RP/0/RP0/CPU0: UTC: l2vpn_mgr[1291]: %L2-EVPN-4-ODN_ON_UNSUPPORTED_ROUTE : EVPN: ODN/AS Nexthop received on unsupported Route-Type 2 (MAC/IP Advertisement), SR-TE BSID tunnel, bridge domain EVPN_ELAN, ESI 0000.0000.0000.0000.0000.
- Associating the access interface (even for SH) with an ESI and coloring per EAD/EVI route to steer the traffic via the SRTE policy:
evi 500
bgp
route-policy export RPL_color_500
!
advertise-mac
l2vpn
bridge group EVPN-ELAN-500
bridge-domain EVPN-ELAN-500
interface HundredGigE0/1/0/2.500
!
evi 500
Verification
RP/0/RSP0/CPU0:ASR9910-3-PE3#show bgp l2vpn evpn rd 10.10.33.33:500
Route Distinguisher: 10.10.33.33:500 (default for vrf EVPN-ELAN-500)
*>i[1][0000.1111.1111.1111.1111][0]/120
10.10.11.11 C:500
100 0 i
*>i[1][0000.1111.1111.1111.1111][4294967295]/120
10.10.11.11 100 0 i
*> [1][0000.2222.2222.2222.2222][0]/120
0.0.0.0 0 i
*>i[3][0][32][10.10.11.11]/80
10.10.11.11 C:500
100 0 i
*> [3][0][32][10.10.33.33]/80
0.0.0.0 0
Note: When PE3 receives Route-type 1 or 3 with extended community color 500 , PE3 initiates ODN SRTE policy 500 which is destined to PE1
Each EVI route is attached with the colo- extended community and is attached to the SRTE policy:
RP/0/RSP0/CPU0:ASR9910-3-PE3#show bgp l2vpn evpn rd 10.10.33.33:500 [1][0000.1111.1111.1111.1111][0]/120
Not advertised to any peer
Local
10.10.11.11 C:500 (bsid:24020) (metric 20) from 10.10.11.11 (10.10.11.11)
Received Label 24015
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install
Received Path ID 0, Local Path ID 1, version 534
Extended community: Color:500 RT:100:500
SR policy color 500, up, registered, bsid 24020, if-handle 0x00000360
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 10.10.11.11:500
The per-ESI route is not colored:
RP/0/RSP0/CPU0:ASR9910-3-PE3# show bgp l2vpn evpn rd 10.10.33.33:500 [1][0000.1111.1111.1111.1111][4294967295]/120
Local
10.10.11.11 (metric 20) from 10.10.11.11 (10.10.11.11)
Received Label 0
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install
Received Path ID 0, Local Path ID 1, version 539
Extended community: EVPN ESI Label:0x01:24017 RT:100:100 RT:100:400 RT:100:500 RT:300:300
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 10.10.11.11:1
Note: The per-ESI route is not colored, as it is associated with multiple EVI and all the EVIs do not take the SRTE path.
Route Type -3 is colored:
RP/0/RSP0/CPU0:ASR9910-3-PE3#show bgp l2vpn evpn rd 10.10.33.33:500 [3][0][32][10.10.11.11]/80
Local
10.10.11.11 C:500 (bsid:24020) (metric 20) from 10.10.11.11 (10.10.11.11)
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported
Received Path ID 0, Local Path ID 1, version 524
Extended community: Color:500 RT:100:500
PMSI: flags 0x00, type 6, label 24016, ID 0x0a0a0b0b
SR policy color 500, up, registered, bsid 24020, if-handle 0x00000360
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 10.10.11.11:500
Route Type 2 is not colored:
RP/0/RSP1/CPU0:ASR9906-1-PE1# show bgp l2vpn evpn rd 10.10.11.11:500 [2][0][48][bce7.12a3.b716][0]/104
Local
10.10.33.33 (metric 10) from 10.10.33.33 (10.10.33.33)
Received Label 24010
Origin IGP, localpref 100, valid, internal, best, group-best, import-candidate, imported, rib-install
Received Path ID 0, Local Path ID 1, version 302
Extended community: SoO:10.10.33.33:500 0x060e:0000.0000.01f4 RT:100:500
EVPN ESI: 0000.2222.2222.2222.2222
Source AFI: L2VPN EVPN, Source VRF: default, Source Route Distinguisher: 10.10.33.33:500
RP/0/RSP0/CPU0:ASR9910-3-PE3#show segment-routing traffic-eng policy color 500
SR-TE policy database
---------------------
Color: 500, End-point: 10.10.11.11
Name: srte_c_500_ep_10.10.11.11
Status:
Admin: up Operational: up for 6d22h
Candidate-paths:
Preference: 200 (BGP ODN) (active)
Requested BSID: dynamic
Constraints:
Protection Type: protected-preferred
Maximum SID Depth: 10
Dynamic (valid)
Metric Type: TE, Path Accumulated Metric: 20
16001 [Prefix-SID, 10.10.1.1]
16005 [Prefix-SID, 10.10.5.5]
16011 [Prefix-SID, 10.10.11.11]
Preference: 100 (BGP ODN) (inactive)
Requested BSID: dynamic
PCC info:
Symbolic name: bgp_c_500_ep_10.10.11.11_discr_100
PLSP-ID: 1
Constraints:
Protection Type: protected-preferred
Maximum SID Depth: 10
Dynamic (pce) (inactive)
Metric Type: NONE, Path Accumulated Metric: 0
Attributes:
Binding SID: 24020
Forward Class: Not Configured
Steering labeled-services disabled: no
Steering BGP disabled: no
IPv6 caps enable: yes
Invalidation drop enabled: no
Max Install Standby Candidate Paths: 0
Unicast traffic for the EVI 500 is sent via SRTE, which can be confirmed by output:
RP/0/RSP0/CPU0:ASR9910-3-PE3#show evpn internal-label vpn-id 500 private
VPN-ID Encap Ethernet Segment Id EtherTag Label
---------- ------ --------------------------- ---------- --------
500 MPLS 0000.1111.1111.1111.1111 0 None
Multi-paths resolved: FALSE (Remote single-active)
Multi-paths Internal label: None
EAD/ES 10.10.11.11 0
Path Version:2, Originating PE:::
EAD/EVI SR-TE BSID 24020
10.10.11.11 24015
Path Version:4, Originating PE:::
Num EAD objects linked: 2
Source: MPLS
Local CW: Unknown
Local MTU: 0
Local ignore MTU mismatch: Enabled
Next path version: 5
Object: EVPN LABEL
Base info: version=0xdbdb000a, flags=0x4000, type=10, reserved=0
EVPN Internal-Label event history [Num events: 16]
----------------------------------------------------------------------------
Time Event Flags Flags
==== ===== ===== =====
Jan 28 19:53:08.224 LSD Label Req (Add/Del) 00000de1 00005dd8 - -
Jan 28 21:29:09.888 Modify Redundant 00000000 00000000 - -
Jan 28 21:29:09.888 Int-Lbl Multi-Path Resolution 01010100 0100020e - -
Jan 28 21:29:09.888 LSD Label Req (Add/Del) 00000add 00100001 - -
Jan 28 21:29:09.888 LSD Label Got 01f40000 01005dd8 - -
Jan 28 23:27:01.632 LSD Label Req (Add/Del) 00000de1 00005dd8 - -
Jan 29 01:06:15.808 Modify Redundant 00000000 00000000 - -
Jan 29 01:06:15.808 Int-Lbl Multi-Path Resolution 01010100 0100020e - -
Jan 29 01:06:15.808 LSD Label Req (Add/Del) 00000add 00100001 - -
Jan 29 01:06:15.808 LSD Label Got 01f40000 01005dd8 - -
Jan 29 03:00:44.416 LSD Label Req (Add/Del) 00000de1 00005dd8 - -
Jan 29 04:45:32.032 Modify Redundant 00000000 00000000 - -
Jan 29 04:45:32.032 Int-Lbl Multi-Path Resolution 01010100 0100020e - -
Jan 29 04:45:32.032 LSD Label Req (Add/Del) 00000add 00100001 - -
Jan 29 04:45:32.032 LSD Label Got 01f40000 01005dd8 - -
Jan 29 06:34:24.000 LSD Label Req (Add/Del) 00000de1 00005dd8 - -
----------------------------------------------------------------------------
Note: 24015 - is the per-EVI label advertised by PE1.
RP/0/RSP0/CPU0:ASR9910-3-PE3#show mpls forwarding labels 24020
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
24020 Pop No ID srte_c_500_e point2point 4182
RP/0/RSP0/CPU0:ASR9910-3-PE3#show l2vpn forwarding bridge-domain EVPN-ELAN-500:EVPN-ELAN-500 evpn inclusive-multicast detail location 0/1/CPU0
Bridge-Domain Name BD-ID XCID TEP-id Next Hop Label/VNI Encap Status E-Tree
-------------------------------- ------ ---------- ---------- -------------------- ---------- -------- ------- ------
EVPN-ELAN-500:EVPN-ELAN-500 2 0x8000000b
Status: bound
Flags: default multicast replication
0x02000001 SRTE BSID 24020 24016 10 bound Root
Note: 24016 - BUM label advertised in route type -3 by PE1.
Conclusion
EVPN over SR-TE brings together the benefits of EVPN’s robust service delivery with the traffic engineering and operational simplicity of SR-TE, resulting in an agile, scalable, and efficient network architecture.
Revision History
| Revision | Publish Date | Comments |
|---|---|---|
1.0 |
14-Feb-2025 |
Initial Release |
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