The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
Segment Routing (SR) is a flexible and scalable way of performing source routing. The source device selects a path and encodes it in the packet header as an ordered list of segments. Segments are identifiers for any type of instruction.
Segment routing for traffic engineering (SR-TE) takes place through a tunnel between a source and destination pair. SR-TE uses the concept of source routing, where the source calculates the path and encodes it in the packet header as a segment. In SR-TE preferred path, each segment is an end-to-end path from the source to the destination, and instructs the routers in the provider core network to follow the specified path instead of the shortest path calculated by the IGP. The destination is unaware of the presence of the tunnel.
The user can achieve better resilience and convergence for the network traffic, by transporting MPLS L2VPN services using segment routing, instead of MPLS LDP. Segment routing can be directly applied to the MPLS architecture without changing the forwarding plane. In a segment-routing network that uses the MPLS data plane, LDP or other signaling protocol is not required; instead label distribution is performed by IGP. Removing protocols from the network simplifies its operation and makes it more robust and stable by eliminating the need for protocol interaction. Segment routing utilizes the network bandwidth more effectively than traditional MPLS networks and offers lower latency.
Preferred tunnel path functionality allows you map pseudowires to specific traffic-engineering tunnel paths. Attachment circuits are cross-connected to specific SR traffic engineering tunnel interfaces instead of remote PE router IP addresses reachable using IGP or LDP. Using preferred tunnel path, the traffic engineering tunnel transports traffic between the source and destination PE routers. A path is selected for an SR Policy when the path is valid and its preference is the best (highest value) among all the candidate paths of the SR Policy.
The following L2VPN services are supported over SR-TE policy:
All L2VPN services such as VPLS, VPWS, and so on must use L2VPN preferred-path while using TE (SR-TE, and RSPV-TE) services as transport. Preferred-path CLI should be set to ensure that the L2VPN traffic is tunnel bound. This will bring up or tear down the L2VPN session based on the tunnel status.
The use of auto-route announce is not recommended as it impacts the way L2VPN tracks the nexthop reachability and causes the L2VPN to be independent of tunnel status.
EVPN VPWS Preferred Path over SR-TE Policy feature allows you to set the preferred path between the two end-points for EVPN VPWS pseudowire (PW) using SR-TE policy. SR policy allows you to choose the path on a per EVPN instance (EVI) basis. This feature is supported on bundle attachment circuit (AC) and physical AC.
If EVPN VPWS with On Demand Next Hop (ODN) is configured, and EVPN VPWS with preferred path is also configured for the same PW, then the preferred-path will take precedence.
EVPN VPWS SR policy is not supported on EVPN VPWS dual homing.
EVPN validates if the route is for a single home next hop, otherwise it issues an error message about a dangling SR TE policy, and continue to set up EVPN-VPWS without it. EVPN relies on ESI value being zero to determine if this is a single home or not. If the AC is a Bundle-Ether interface running LACP then you need to manually configure the ESI value to zero to overwrite the auto-sense ESI as EVPN VPWS multihoming is not supported.
evpn
interface Bundle-Ether12
ethernet-segment
identifier type 0 00.00.00.00.00.00.00.00.00
/* Or globally */
Evpn
ethernet-segment type 1 auto-generation-disable
Consider a topology where PE1 and PE3 are the two EVPN VPWS PW end-points. Traffic is sent from PE1 to PE3 through SR in the core. Traffic from PE1 can be sent to PE3 either through P1 or P2 node. In this example, the EVPN VPWS preferred path over SR policy is configured to show the traffic flow from PE1 to PE3 using prefix-SID. Using adjacency-SID, you can steer traffic flow from PE1 to PE3 and specify whether it should pass through P1 or P2 node.
You must complete these tasks to ensure the successful configuration of EVPN VPWS Preferred Path over SR-TE Policy feature:
Configure Prefix-SID on IGP — The following examples show how to configure prefix-SID in IS-IS.
Configure Adjacency-SID on IGP — The following examples show how to configure Adjacency-SID in IS-IS.
Configure segment-list
Configure SR-TE policy
Configure EVPN VPWS over SR-TE policy
/* Configure Prefix-SID on PE1 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 180000 200000
Router(config-sr)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# is-type level-2-only
Route(config-isis)# net 49.0002.0330.2000.0031.00
Route(config-isis)# nsr
Route(config-isis)# nsf ietf
Route(config-isis)# log adjacency changes
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide level 2
Route(config-isis-af)# mpls traffic-eng level-2-only
Route(config-isis-af)# mpls traffic-eng router-id 10.0.0.1
Route(config-isis-af)# segment-routing mpls sr-prefer
Route(config-isis-af)# segment-routing prefix-sid-map advertise-local
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback 0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 180010
Route(config-isis-af)# commit
Route(config-isis-af)# exit
/* Configure Prefix-SID on P1 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 180000 200000
Router(config-sr)# exit
!
Router# configure
Router(config)# router isis core
Router(config-isis)# is-type level-2-only
Router(config-isis)# net 49.0002.0330.2000.0021.00
Router(config-isis)# nsr
Router(config-isis)# nsf ietf
Router(config-isis)# log adjacency changes
Router(config-isis)# address-family ipv4 unicast
Router(config-isis-af)# metric-style wide level 2
Router(config-isis-af)# mpls traffic-eng level-2-only
Router(config-isis-af)# mpls traffic-eng router-id loopback0
Router(config-isis-af)# segment-routing mpls sr-prefer
Router(config-isis-af)# segment-routing prefix-sid-map advertise-local
Router(config-isis-af)# exit
!
Router(config-isis)# interface loopback 0
Router(config-isis-if)# address-family ipv4 unicast
Router(config-isis-af)# prefix-sid index 180015
Router(config-isis-af)# commit
Router(config-isis-af)# exit
/* Configure Prefix-SID on P2 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 180000 200000
Router(config-sr)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# is-type level-2-only
Route(config-isis)# net 49.0002.0330.2000.0022.00
Route(config-isis)# nsr
Route(config-isis)# nsf ietf
Route(config-isis)# log adjacency changes
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide level 2
Route(config-isis-af)# mpls traffic-eng level-2-only
Route(config-isis-af)# mpls traffic-eng router-id loopback0
Route(config-isis-af)# segment-routing mpls sr-prefer
Route(config-isis-af)# segment-routing prefix-sid-map advertise-local
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback 0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 180025
Route(config-isis-af)# commit
Route(config-isis-af)# exit
/* Configure Prefix-SID on PE3 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 180000 200000
Router(config-sr)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# is-type level-2-only
Route(config-isis)# net 49.0002.0330.2000.3030.0030.0035.00
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide level 2
Route(config-isis-af)# mpls traffic-eng level-2-only
Route(config-isis-af)# mpls traffic-eng router-id loopback0
Route(config-isis-af)# segment-routing mpls sr-prefer
Route(config-isis-af)# segment-routing prefix-sid-map advertise-local
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 180020
Route(config-isis-af)# commit
Route(config-isis-af)# exit
/* Configure Adjacency-SID on PE1 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# local-block 15000 15999
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface Bundle-Ether121
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15101
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/1/6
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15102
Route(config-isis-if-af)# commit
/* Configure Adjacency-SID on P1 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# local-block 15000 15999
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface Bundle-Ether121
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# metric 20
Route(config-isis-if-af)# adjacency-sid absolute 15200
Route(config-isis-if-af)# commit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/7
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15202
Route(config-isis-if-af)# commit
!
/* Configure Adjacency-SID on P2 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# local-block 15000 15999
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/7
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# metric 20
Route(config-isis-if-af)# adjacency-sid absolute 15201
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/5
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# metric 20
Route(config-isis-if-af)# adjacency-sid absolute 15204
Route(config-isis-if-af)# commit
/* Configure Adjacency-SID on PE3 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# local-block 15000 15999
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/1
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15301
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/2
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15302
Route(config-isis-if-af)# commit
/* Configure Segment-list on PE1 using prefix-SID */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 180000 200000
Router(config-sr)# traffic-eng
Router(config-sr-te)# logging
Router(config-sr-te-log)# policy status
Router(config-sr-te-log)# exit
!
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# segment-list name pref_sid_to_PE3
Router(config-sr-te-sl)# index 1 mpls label 180020 <-----------------------using prefix-SID
Router(config-sr-te-sl)# exit
/* Configure Segment-list on PE1 using adjacency-SID */
Router# configure
Router(config)# segment-routing
Router(config-sr)# local-block 15000 15999
Router(config-sr)# traffic-eng
Router(config-sr-te)# logging
Router(config-sr-te-log)# policy status
Router(config-sr-te-log)# exit
!
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# segment-list name pref_adj_sid_to_PE3
Router(config-sr-te-sl)# index 1 mpls label 15101 <-----------------------using adjacency-SID
Router(config-sr-te-sl)# index 2 mpls label 15202 <-----------------------using adjacency-SID
Router(config-sr-te-sl)# exit
/* Configure SR-TE Policy */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy pref_sid_to_PE3
Router(config-sr-te-policy)# color 9001 end-point ipv4 172.16.0.1
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 10
Router(config-sr-te-pp-info)# explicit segment-list pref_sid_to_PE3
Router(config-sr-te-pp-info)# commit
Router(config-sr-te-pp-info)# exit
!
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy pref_adj_sid_to_PE3
Router(config-sr-te-policy)# color 9001 end-point ipv4 172.16.0.1
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 200
Router(config-sr-te-pp-info)# explicit segment-list pref_adj_sid_to_PE3
Router(config-sr-te-pp-info)# commit
Router(config-sr-te-pp-info)# exit
/* You can configure multiple preferences for an SR policy. Among the configured preferences, the largest number takes the highest precedence */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 180000 200000
Router(config-sr)# local-block 15000 15999
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy 1013
Router(config-sr-te-policy)# color 1013 end-point ipv4 2.2.2.2
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-pp-info)# explicit segment-list PE1-P1_BE121
Router(config-sr-te-pp-info)# exit
!
Router(config-sr-te-policy-path)# preference 200
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE3-P1-t0016
Router(config-sr-te-pp-info)# exit
!
Router(config-sr-te-policy-path)# preference 700 <----------largest number takes the precendence
Router(config-sr-te-pp-info)# explicit segment-list PE1-P1
Router(config-sr-te-pp-info)# commit
Router(config-sr-te-pp-info)# exit
 Note |
Use the auto-generated SR-TE policy name to attach the policy to the L2VPN instance. The auto-generated policy name is based on the policy color and end-point. Use the show segment-routing traffic-eng policy candidate-path name policy_name command to display the auto-generated policy name. |
Router# show segment-routing traffic-eng policy candidate-path name pref_sid_to_PE3
SR-TE policy database
---------------------
Color: 9001, End-point: 172.16.0.1
Name: srte_c_9001_ep_172.16.0.1
Router# configure
Router(config)# l2vpn
Router(config-l2vpn)# pw-class 1001
Router(config-l2vpn-pwc)# encapsulation mpls
Router(config-l2vpn-pwc-mpls)# preferred-path sr-te policy srte_c_9001_ep_172.16.0.1 fallback disable
Router(config-l2vpn-pwc-mpls)# commit
Router(config-l2vpn-pwc-mpls)# exit
!
Router(config)# l2vpn
Router(config-l2vpn)# xconnect group evpn_vpws
Router(config-l2vpn-xc)# p2p evpn_vpws_1001
Router(config-l2vpn-xc-p2p)# interface tengi0/1/0/1.1001
Router(config-l2vpn-xc-p2p)# neighbor evpn evi 1001 target 10001 source 20001
Router(config-l2vpn-xc-p2p-pw)# pw-class 1001
Router(config-l2vpn-xc-p2p-pw)# commit
Router(config-l2vpn-xc-p2p-pw)# exit
/* If Fallback Enable is configured, which is the default option, and if the SR-policy is down, then EVPN VPWS will still continue to be UP using the regular IGP path, and not using the SR-policy */
show l2vpn xconnect detail
EVPN: neighbor 172.16.0.1, PW ID: evi 1001, ac-id 10001, state is up ( established )
Preferred path Inactive : SR TE srte_c_9001_ep_172.16.0.1, Statically configured, fallback enabled
Tunnel : Down
LSP: Up
/* If Fallback Disable is configured, and if the SR-policy is down, or if it misconfigured in dual homed mode, then the L2VPN PW will be down */
show l2vpn xconnect detail
EVPN: neighbor 172.16.0.1, PW ID: evi 1001, ac-id 10001, state is down ( local ready )
Preferred path Active : SR TE srte_c_9001_ep_172.16.0.1, Statically configured, fallback disabled
Tunnel : Down
/* Configure Prefix-SID in ISIS */
PE1:
configure
segment-routing
global-block 180000 200000
!
router isis core
is-type level-2-only
net 49.0002.0330.2000.0031.00
nsr
nsf ietf
log adjacency changes
address-family ipv4 unicast
metric-style wide level 2
mpls traffic-eng level-2-only
mpls traffic-eng router-id 10.0.0.1
segment-routing mpls sr-prefer
segment-routing prefix-sid-map advertise-local
interface Loopback0
address-family ipv4 unicast
prefix-sid index 180010
P1:
configure
segment-routing
global-block 180000 200000
router isis core
is-type level-2-only
net 49.0002.0330.2000.0021.00
nsr
nsf ietf
log adjacency changes
address-family ipv4 unicast
metric-style wide level 2
mpls traffic-eng level-2-only
mpls traffic-eng router-id Loopback0
segment-routing mpls sr-prefer
segment-routing prefix-sid-map advertise-local
interface Loopback0
address-family ipv4 unicast
prefix-sid index 180015
P2:
configure
segment-routing
global-block 180000 200000
router isis core
is-type level-2-only
net 49.0002.0330.2000.0022.00
nsr
nsf ietf
log adjacency changes
address-family ipv4 unicast
metric-style wide level 2
mpls traffic-eng level-2-only
mpls traffic-eng router-id Loopback0
segment-routing mpls sr-prefer
segment-routing prefix-sid-map advertise-local
interface Loopback0
address-family ipv4 unicast
prefix-sid index 180025
PE3:
configure
segment-routing
global-block 180000 200000
router isis core
is-type level-2-only
net 49.0002.0330.2000.3030.0030.0035.00
address-family ipv4 unicast
metric-style wide level 2
mpls traffic-eng level-2-only
mpls traffic-eng router-id Loopback0
segment-routing mpls sr-prefer
segment-routing prefix-sid-map advertise-local
interface Loopback0
address-family ipv4 unicast
prefix-sid index 180020
/* Configure Adjacency-SID in ISIS */
PE1:
configure
segment-routing
local-block 15000 15999
!
router isis core
!
interface Bundle-Ether121
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15101
interface TenGigE0/0/1/6
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15102
P1:
configure
segment-routing
local-block 15000 15999
router isis core
!
interface Bundle-Ether121
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
metric 20
adjacency-sid absolute 15200
interface TenGigE0/0/0/0/7
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
metric 20
adjacency-sid absolute 15202
P2:
configure
segment-routing
local-block 15000 15999
router isis core
!
interface TenGigE0/0/0/5
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
metric 20
adjacency-sid absolute 15204
interface TenGigE0/0/0/0/7
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
metric 20
adjacency-sid absolute 15201
PE3:
configure
segment-routing
local-block 15000 15999
router isis core
!
interface TenGigE0/0/0/1
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15301
!
!
interface TenGigE0/0/0/2
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15302
/* Configure Segment-list */
PE1:
configure
segment-routing
global-block 180000 200000
traffic-eng
logging
policy status
segment-routing
traffic-eng
segment-list name pref_sid_to_PE3
index 1 mpls label 180020
!
!
configure
segment-routing
local-block 15000 15999
traffic-eng
logging
policy status
segment-routing
traffic-eng
segment-list name pref_adj_sid_to_PE3
index 1 mpls label 15101
index 2 mpls label 15202
!
!
/* Configure SR-TE policy */
segment-routing
traffic-eng
policy pref_sid_to_PE3
color 9001 end-point ipv4 172.16.0.1
candidate-paths
preference 10
explicit segment-list pref_sid_to_PE3
!
!
segment-routing
traffic-eng
policy pref_adj_sid_to_PE3
color 9001 end-point ipv4 172.16.0.1
candidate-paths
preference 200
explicit segment-list pref_adj_sid_to_PE3
!
!
/* You can configure multiple preferences for an SR policy. Among the configured preferences, the largest number takes the highest precedence */
segment-routing
traffic-eng
policy 1013
color 1013 end-point ipv4 2.2.2.2
candidate-paths
preference 100
explicit segment-list PE1-P1_BE121
!
preference 200
explicit segment-list PE1-PE3-P1-t0016
!
preference 700
explicit segment-list PE1-P1
!
/* Configure EVPN VPWS over SR-TE policy */
PE1:
configure
l2vpn
pw-class 1001
encapsulation mpls
preferred-path sr-te policy srte_c_9001_ep_172.16.0.1 fallback disable
xconnect group evpn_vpws
p2p evpn_vpws_1001
interface tengi0/1/0/1.1001
neighbor evpn evi 1001 target 10001 source 20001
pw-class 1001
!
PE1#show segment-routing traffic-eng forwarding policy name pref_sid_to_PE3 detail
Policy Segment Outgoing Outgoing Next Hop Bytes
Name List Label Interface Switched
------------- --------------- ----------- ------------------- --------------- ------------
pref_sid_to_PE3
15102 TenGigE0/0/1/6 172.16.0.1 81950960
Label Stack (Top -> Bottom): { 15101, 15102 }
Path-id: 1, Weight: 0
Packets Switched: 787990
Local label: 34555
Packets/Bytes Switched: 1016545/105720680
(!): FRR pure backup
PE1#show segment-routing traffic-eng policy candidate-path name pref_sid_to_PE3
SR-TE policy database
---------------------
Color: 9001, End-point: 172.16.0.1
Name: srte_c_9001_ep_172.16.0.1
PE1#show mpls forwarding tunnels sr-policy name pref_sid_to_PE3
Tunnel Outgoing Outgoing Next Hop Bytes
Name Label Interface Switched
------------- ----------- ------------ --------------- ------------
pref_sid_to_PE3 (SR) 15102 TenGigE0/0/1/6 172.16.0.1 836516512
PE1#show l2vpn xconnect group evpn_vpws xc-name evpn_vpws_1001 detail
Group evpn_vpws, XC evpn_vpws_1001, state is up; Interworking none
AC: Bundle-Ether12.1001, state is up
Type VLAN; Num Ranges: 1
Outer Tag: 1000
Rewrite Tags: []
VLAN ranges: [1, 1]
MTU 1500; XC ID 0xc0000018; interworking none
Statistics:
packets: received 642304, sent 642244
bytes: received 61661184, sent 61655424
drops: illegal VLAN 0, illegal length 0
EVPN: neighbor 172.16.0.1, PW ID: evi 1001, ac-id 10001, state is up ( established )
XC ID 0xa0000007
Encapsulation MPLS
Source address 10.10.10.10
Encap type Ethernet, control word enabled
Sequencing not set
Preferred path Active : SR TE pref_sid_to_PE3, Statically configured, fallback disabled
Tunnel : Up
Load Balance Hashing: src-dst-mac
adjacency-sid
index
prefix-sid
segment-routing
The applicable segment routing commands are described in the Segment Routing Command Reference for Cisco NCS 5500 Series Routers and Cisco NCS 540 Series Routers
All L2VPN services such as VPLS, VPWS, and so on must use L2VPN preferred-path while using TE (SR-TE, and RSPV-TE) services as transport.
L2VPN VPWS Preferred Path over SR-TE Policy feature allows you to set the preferred path between the two end-points for L2VPN Virtual Private Wire Service (VPWS) using SR-TE policy.
Perform the following steps to configure L2VPN VPWS Preferred Path over SR-TE Policy feature. The following figure is used as a reference to explain the configuration steps.
Configure Prefix-SID on IGP — The following examples show how to configure prefix-SID in IS-IS.
Configure Adjacency-SID on IGP — The following examples show how to configure Adjacency-SID in IS-IS.
Configure segment-list
Configure SR-TE policy
Configure VPWS over SR-TE policy
/* Configure Prefix-SID on PE1 */
Router# configure
Route(config)# router isis core
Route(config-isis)# is-type level-2-only
Route(config-isis)# net 49.0002.0330.2000.0031.00
Route(config-isis)# nsr
Route(config-isis)# nsf ietf
Route(config-isis)# log adjacency changes
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide level 2
Route(config-isis-af)# mpls traffic-eng level-2-only
Route(config-isis-af)# mpls traffic-eng router-id 10.0.0.1
Route(config-isis-af)# segment-routing mpls sr-prefer
Route(config-isis-af)# segment-routing prefix-sid-map advertise-local
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback 0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 16100
Route(config-isis-af)# commit
Route(config-isis-af)# exit
/* Configure Prefix-SID on PE2 */
Router# configure
Route(config)# router isis core
Route(config-isis)# is-type level-2-only
Route(config-isis)# net 49.0002.0330.2000.0021.00
Route(config-isis)# nsr
Route(config-isis)# nsf ietf
Route(config-isis)# log adjacency changes
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide level 2
Route(config-isis-af)# mpls traffic-eng level-2-only
Route(config-isis-af)# mpls traffic-eng router-id loopback0
Route(config-isis-af)# segment-routing mpls sr-prefer
Route(config-isis-af)# segment-routing prefix-sid-map advertise-local
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback 0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 16200
Route(config-isis-af)# commit
Route(config-isis-af)# exit
/* Configure Prefix-SID on PE3 */
Router# configure
Route(config)# router isis core
Route(config-isis)# is-type level-2-only
Route(config-isis)# net 49.0002.0330.2000.3030.0030.0035.00
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide level 2
Route(config-isis-af)# mpls traffic-eng level-2-only
Route(config-isis-af)# mpls traffic-eng router-id loopback0
Route(config-isis-af)# segment-routing mpls sr-prefer
Route(config-isis-af)# segment-routing prefix-sid-map advertise-local
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback 0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 16300
Route(config-isis-af)# commit
Route(config-isis-af)# exit
/* Configure Adjacency-SID on PE1 */
Router# configure
Route(config)# router isis core
Route(config-isis)# interface Bundle-Ether121
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15100
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/1/6
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15101
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/1/9
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15102
Route(config-isis-if-af)# commit
/* Configure Adjacency-SID on PE2 */
Router# configure
Route(config)# router isis core
Route(config-isis)# interface Bundle-Ether121
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15200
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/1/4
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15201
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/7
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15202
Route(config-isis-if-af)# commit
/* Configure Adjacency-SID on PE3 */
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/1
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15301
Route(config-isis-if-af)# exit
!
Router# configure
Route(config)# router isis core
Route(config-isis)# interface TenGigE0/0/0/2
Route(config-isis-if)# circuit-type level-2-only
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-if-af)# adjacency-sid absolute 15302
Route(config-isis-if-af)# commit
/* Configure segment-list on PE1 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 16000 23999
Router(config-sr)# local-block 15000 15999
Router(config-sr)# traffic-eng
Router(config-sr-te)# segment-list segment-list name PE1-PE2
Router(config-sr-te-sl)# index 1 mpls label 16200
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE1-PE3
Router(config-sr-te-sl)# index 1 mpls label 16300
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE1-PE2-PE3
Router(config-sr-te-sl)# index 1 mpls label 16200
Router(config-sr-te-sl)# index 2 mpls label 16300
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE1-PE2_bad
Router(config-sr-te-sl)# index 1 mpls label 16900
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE1-PE3-PE2
Router(config-sr-te-sl)# index 1 mpls label 16300
Router(config-sr-te-sl)# index 2 mpls label 16200
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE1-PE2_BE121
Router(config-sr-te-sl)# index 1 mpls label 15100
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE1-PE3-PE2_link
Router(config-sr-te-sl)# index 1 mpls label 15101
Router(config-sr-te-sl)# index 2 mpls label 15302
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE1-PE3-PE2-t0016
Router(config-sr-te-sl)# index 1 mpls label 15101
Router(config-sr-te-sl)# index 2 mpls label 16200
Router(config-sr-te-sl)# commit
/* Configure segment-list on PE2 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 16000 23999
Router(config-sr)# local-block 15000 15999
Router(config-sr)# traffic-eng
Router(config-sr-te)# segment-list segment-list name PE2-PE1
Router(config-sr-te-sl)# index 1 mpls label 16100
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE2-PE3-PE1
Router(config-sr-te-sl)# index 1 mpls label 16300
Router(config-sr-te-sl)# index 2 mpls label 16100
Router(config-sr-te-sl)# commit
/* Configure segment-list on PE3 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 16000 23999
Router(config-sr)# local-block 15000 15999
Router(config-sr)# traffic-eng
Router(config-sr-te)# segment-list segment-list name PE3-PE1
Router(config-sr-te-sl)# index 1 mpls label 16100
Router(config-sr-te-sl)# exit
!
Router(config-sr-te)# segment-list segment-list name PE3-PE2-PE1
Router(config-sr-te-sl)# index 1 mpls label 16200
Router(config-sr-te-sl)# index 2 mpls label 16100
Router(config-sr-te-sl)# commit
/* Configure SR-TE policy */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy 100
Router(config-sr-te-policy)# color 1 end-point ipv4 172.16.0.1
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy)# preference 400
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE3-PE2
Router(config-sr-te-pp-info)# exit
!
Router(config-sr-te-policy)# preference 500 <-----------------largest number takes the precedence
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE2
Router(config-sr-te-pp-info)# commit
Router(config-sr-te-pp-info)# exit
!
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy 1013
Router(config-sr-te-policy)# color 1013 end-point ipv4 172.16.0.1
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy)# preference 100
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE2_BE121
Router(config-sr-te-pp-info)# exit
!
Router(config-sr-te-policy)# preference 200
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE3-PE2-t0016
Router(config-sr-te-pp-info)# exit
!
Router(config-sr-te-policy)# preference 500
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE2
Router(config-sr-te-pp-info)# exit
!
Router(config-sr-te-policy)# preference 600
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE3-PE2
Router(config-sr-te-pp-info)# exit
!
Router(config-sr-te-policy)# preference 700
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE3-PE2_link
Router(config-sr-te-pp-info)# commit
!
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# policy 1300
Router(config-sr-te-policy)# color 1300 end-point ipv4 192.168.0.1
Router(config-sr-te-policy)# candidate-paths
Router(config-sr-te-policy)# preference 100
Router(config-sr-te-pp-info)# explicit segment-list PE1-PE3
Router(config-sr-te-pp-info)# commit
!
Note |
Use the auto-generated SR-TE policy name to attach the policy to the L2VPN instance. The auto-generated policy name is based on the policy color and end-point. Use the show segment-routing traffic-eng policy candidate-path name policy_name command to display the auto-generated policy name. |
Router# show segment-routing traffic-eng policy candidate-path name 1300
SR-TE policy database
---------------------
Color: 1300, End-point: 192.168.0.1
Name: srte_c_1300_ep_192.168.0.1
Router# configure
Router(config)# l2vpn
Router(config-l2vpn)# pw-class pw1300
Router(config-l2vpn-pwc)# encapsulation mpls
Router(config-l2vpn-pwc-mpls)# load-balancing
Router(config-l2vpn-pwc-mpls-load-bal)# flow-label both
Router(config-l2vpn-pwc-mpls-load-bal)# exit
!
Router(config-l2vpn-pwc-mpls)# preferred-path sr-te policy srte_c_1300_ep_192.168.0.1 fallback disable
Router(config-l2vpn-pwc-mpls)# exit
!
Router(config)# l2vpn
Router(config-l2vpn)# xconnect group xcon1
Router(config-l2vpn-xc)# p2p vplw1002
Router(config-l2vpn-xc-p2p)# interface TenGigE0/0/1/1.1002
Router(config-l2vpn-xc-p2p)# neighbor 192.168.0.1 pw-id 1002
Router(config-l2vpn-xc-p2p-pw)# pw-class pw1300
Router(config-l2vpn-xc-p2p-pw)# commit
Router(config-l2vpn-xc-p2p-pw)# exit
/* Configure prefix-SID */
PE1:
router isis core
is-type level-2-only
net 49.0002.0330.2000.0031.00
nsr
nsf ietf
log adjacency changes
address-family ipv4 unicast
metric-style wide level 2
mpls traffic-eng level-2-only
mpls traffic-eng router-id 10.0.0.1
segment-routing mpls sr-prefer
segment-routing prefix-sid-map advertise-local
interface Loopback0
address-family ipv4 unicast
prefix-sid index 16100
PE2:
router isis core
is-type level-2-only
net 49.0002.0330.2000.0021.00
nsr
nsf ietf
log adjacency changes
address-family ipv4 unicast
metric-style wide level 2
mpls traffic-eng level-2-only
mpls traffic-eng router-id Loopback0
segment-routing mpls sr-prefer
segment-routing prefix-sid-map advertise-local
interface Loopback0
address-family ipv4 unicast
prefix-sid index 16200
PE3:
router isis core
is-type level-2-only
net 49.0002.0330.2000.3030.0030.0035.00
address-family ipv4 unicast
metric-style wide level 2
mpls traffic-eng level-2-only
mpls traffic-eng router-id Loopback0
segment-routing mpls sr-prefer
segment-routing prefix-sid-map advertise-local
interface Loopback0
address-family ipv4 unicast
prefix-sid index 16300
/* Configure Adjacency-SID */
PE1:
router isis core
!
interface Bundle-Ether121
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15100
!
interface TenGigE0/0/1/6
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15101
!
interface TenGigE0/0/1/9
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15102
PE2
router isis core
!
interface Bundle-Ether121
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15200
interface TenGigE0/0/0/0/4
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15201
interface TenGigE0/0/0/0/7
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15202
PE3:
router isis core
!
interface TenGigE0/0/0/1
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15301
!
!
interface TenGigE0/0/0/2
circuit-type level-2-only
point-to-point
hello-padding disable
address-family ipv4 unicast
adjacency-sid absolute 15302
/* Configure segment-list */
PE1:
segment-routing
global-block 16000 23999
local-block 15000 15999
traffic-eng
segment-list name PE1-PE2
index 1 mpls label 16200
!
segment-list name PE1-PE3
index 1 mpls label 16300
!
segment-list name PE1-PE2-PE3
index 1 mpls label 16200
index 2 mpls label 16300
!
segment-list name PE1-PE2_bad
index 1 mpls label 16900
!
segment-list name PE1-PE3-PE2
index 1 mpls label 16300
index 2 mpls label 16200
!
segment-list name PE1-PE2_BE121
index 1 mpls label 15100
!
segment-list name PE1-PE3-PE2_link
index 1 mpls label 15101
index 2 mpls label 15302
!
segment-list name PE1-PE3-PE2-t0016
index 1 mpls label 15101
index 2 mpls label 16200
PE2:
segment-routing
global-block 16000 23999
local-block 15000 15999
traffic-eng
segment-list name PE2-PE1
index 1 mpls label 16100
!
segment-list name PE2-PE3-PE1
index 1 mpls label 16300
index 2 mpls label 16100
PE3:
segment-routing
global-block 16000 23999
local-block 15000 15999
traffic-eng
segment-list name PE3-PE1
index 1 mpls label 16100
!
segment-list name PE3-PE2-PE1
index 1 mpls label 16200
index 2 mpls label 16100
/* Configure SR-TE policy */
segment-routing
traffic-eng
policy 100
color 1 end-point ipv4 172.16.0.1
candidate-paths
preference 400
explicit segment-list PE1-PE3-PE2
!
preference 500
explicit segment-list PE1-PE2
policy 1013
color 1013 end-point ipv4 172.16.0.1
candidate-paths
preference 100
explicit segment-list PE1-PE2_BE121
!
preference 200
explicit segment-list PE1-PE3-PE2-t0016
!
preference 500
explicit segment-list PE1-PE2
!
preference 600
explicit segment-list PE1-PE3-PE2
!
preference 700
explicit segment-list PE1-PE3-PE2_link
!
policy 1300
color 1300 end-point ipv4 192.168.0.1
candidate-paths
preference 100
explicit segment-list PE1-PE3
!
/*Configure VPWS over SR-TE policy
l2vpn
pw-class pw1300
encapsulation mpls
load-balancing
flow-label both
preferred-path sr-te policy srte_c_1300_ep_192.168.0.1 fallback disable
Xconnect group xcon1
p2p vplw1002
interface TenGigE0/0/1/1.1002
neighbor 192.168.0.1 pw-id 1002
pw-class pw1300
/* The prefix-sid and Adjacency-sid must be in the SR topology */
PE1#show segment-routing traffic-eng ipv4 topology | inc Prefix
Thu Feb 1 20:28:43.343 EST
Prefix SID:
Prefix 10.0.0.1, label 16100 (regular)
Prefix SID:
Prefix 192.168.0.1, label 16300 (regular)
Prefix SID:
Prefix 172.16.0.1, label 16200 (regular)
PE1#show segment-routing traffic-eng ipv4 topology | inc Adj SID
Thu Feb 1 20:30:25.760 EST
Adj SID: 61025 (unprotected) 15102 (unprotected)
Adj SID: 61023 (unprotected) 15101 (unprotected)
Adj SID: 65051 (unprotected) 15100 (unprotected)
Adj SID: 41516 (unprotected) 15301 (unprotected)
Adj SID: 41519 (unprotected) 15302 (unprotected)
Adj SID: 46660 (unprotected) 15201 (unprotected)
Adj SID: 24003 (unprotected) 15202 (unprotected)
Adj SID: 46675 (unprotected) 15200 (unprotected)
PE1# show segment-routing traffic-eng policy candidate-path name 100
SR-TE policy database
---------------------
Color: 100, End-point: 172.16.0.1
Name: srte_c_1_ep_172.16.0.1
PE1#show segment-routing traffic-eng policy name 100
Thu Feb 1 23:16:58.368 EST
SR-TE policy database
---------------------
Name: 100 (Color: 1, End-point: 172.16.0.1)
Status:
Admin: up Operational: up for 05:44:25 (since Feb 1 17:32:34.434)
Candidate-paths:
Preference 500:
Explicit: segment-list PE1-PE2 (active)
Weight: 0, Metric Type: IGP
16200 [Prefix-SID, 172.16.0.1]
Preference 400:
Explicit: segment-list PE1-PE3-PE2 (inactive)
Inactive Reason: unresolved first label
Weight: 0, Metric Type: IGP
Attributes:
Binding SID: 27498
Allocation mode: dynamic
State: Programmed
Policy selected: yes
Forward Class: 0
PE1#show segment-routing traffic-eng policy name 1013
Thu Feb 1 21:20:57.439 EST
SR-TE policy database
---------------------
Name: 1013 (Color: 1013, End-point: 172.16.0.1)
Status:
Admin: up Operational: up for 00:06:36 (since Feb 1 21:14:22.057)
Candidate-paths:
Preference 700:
Explicit: segment-list PE1-PE3-PE2_link (active)
Weight: 0, Metric Type: IGP
15101 [Adjacency-SID, 13.1.1.1 - 13.1.1.2]
15302
Preference 600:
Explicit: segment-list PE1-PE3-PE2 (inactive)
Inactive Reason:
Weight: 0, Metric Type: IGP
Preference 500:
Explicit: segment-list PE1-PE2 (inactive)
Inactive Reason:
Weight: 0, Metric Type: IGP
Preference 200:
Explicit: segment-list PE1-PE3-PE2-t0016 (inactive)
Inactive Reason: unresolved first label
Weight: 0, Metric Type: IGP
Preference 100:
Explicit: segment-list PE1-PE2_BE121 (inactive)
Inactive Reason: unresolved first label
Weight: 0, Metric Type: IGP
Attributes:
Binding SID: 27525
Allocation mode: dynamic
State: Programmed
Policy selected: yes
Forward Class: 0
PE1#show segment-routing traffic-eng forwarding policy name 100
Thu Feb 1 23:19:28.951 EST
Policy Segment Outgoing Outgoing Next Hop Bytes
Name List Label Interface Switched
------------- --------------- ----------- ------------------- --------------- ------------
100 PE1-PE2 Pop Te0/0/1/9 12.1.9.2 0
Pop BE121 121.1.0.2 0
PE1#show segment-routing traffic-eng forwarding policy name 1013 detail
Thu Feb 1 21:22:46.069 EST
Policy Segment Outgoing Outgoing Next Hop Bytes
Name List Label Interface Switched
------------- --------------- ----------- ------------------- --------------- ------------
1013 PE1-PE3-PE2_link
15302 Te0/0/1/6 13.1.1.2 0
Label Stack (Top -> Bottom): { 15302 }
Path-id: 1, Weight: 0
Packets Switched: 0
Local label: 24005
Packets/Bytes Switched: 0/0
(!): FRR pure backup
PE1#show mpls forwarding tunnels sr-policy name 1013
Thu Feb 1 21:23:22.743 EST
Tunnel Outgoing Outgoing Next Hop Bytes
Name Label Interface Switched
------------- ----------- ------------ --------------- ------------
1013 (SR) 15302 Te0/0/1/6 13.1.1.2 0
adjacency-sid
index
prefix-sid
segment-routing
The applicable segment routing commands are described in the Segment Routing Command Reference for Cisco NCS 5500, NCS 540 Series Routers, and NCS 560 Series Routers.
The EVPN VPWS On-Demand Next Hop with SR-TE feature enables you to fetch the best path to send traffic from the source to destination in a point-to-point service using IOS XR Traffic Controller (XTC). On-Demand Next Hop (ODN) with SR-TE is supported on EVPN Virtual Private Wire Service (VPWS) and Flexible Cross Connect (FXC) VLAN-unaware service.
When redistributing routing information across domains, provisioning of multi-domain services (Layer2 VPN and Layer 3 VPN) poses complexity and scalability issues. ODN with SR-TE feature delegates computation of an end-to-end Label Switched Path (LSP) to a path computation element (PCE). This PCE includes constraints and policies without any redistribution. It then installs the reapplied multi-domain LSP for the duration of the service into the local forwarding information base(FIB).
ODN uses BGP dynamic SR-TE capabilities and adds the path to the PCE. The PCE has the ability to find and download the end-to-end path based on the requirements. ODN triggers an SR-TE auto-tunnel based on the defined BGP policy. The PCE learns real-time topologies through BGP and/or IGP.
The path computation element (PCE) describes a set of procedures by which a path computation client (PCC) reports and delegates control of head-end tunnels sourced from the PCC to a PCE peer. The PCE peer requests the PCC to update and modify parameters of LSPs it controls. It also enables a PCC to allow the PCE to initiate computations and to perform network-wide orchestration.
Maximum number of auto-provisioned TE policies is 1000.
EVPN validates if the route is for a single home next hop, otherwise it issues an error message about a dangling SR-TE policy, and continue to setup EVPN-VPWS without it. EVPN relies on ESI value being zero to determine if this is a single home or not.
evpn
interface Bundle-Ether12
ethernet-segment
identifier type 0 00.00.00.00.00.00.00.00.00
/* Or globally */
evpn
ethernet-segment type 1 auto-generation-disablePerform the following steps to configure EVPN VPWS On Demand Next Hop with SR-TE. The following figure is used as a reference to explain the configuration steps:
Configure Prefix-SID in ISIS
Configure SR-TE
Configure PCE and PCC
Configure SR color
Configure EVPN route policy
Configure BGP
Configure EVPN VPWS
Configure Flexible Cross-connect Service (FXC) VLAN-unaware
Consider a topology where EVPN VPWS is configured on PE1 and PE2. Traffic is sent from PE1 to PE2 using SR-TE in the core. The PCE, which is configured on the P router, calculates the best path from PE1 to PE2. Path computation client (PCC) is configured on PE1 and PE2.
Configure Prefix-SID in ISIS and topology-independent loop-free alternate path (TI-LFA) in the core such that each router uses a unique segment identifier associated with the prefix.
/* Configure Prefix-SID in ISIS and TI-LFA on PE1 */
Router# configure
Route(config)# router isis ring
Route(config-isis)# is-type level-2-only
Route(config-isis)# net 49.0001.1921.6800.1001.00
Route(config-isis)# segment-routing global-block 30100 39100
Route(config-isis)# nsr
Route(config-isis)# distribute link-state
Route(config-isis)# nsf cisco
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide
Route(config-isis-af)# mpls traffic-eng level-1
Route(config-isis-af)# mpls traffic-eng router-id loopback0
Route(config-isis-af)# segment-routing mpls
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 30101
Route(config-isis-af)# exit
!
Route(config-isis)# interface HundredGigE0/0/0/0
Route(config-isis-if)# circuit-type level-1
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# fast-reroute per-prefix
Route(config-isis-if-af)# fast-reroute per-prefix ti-lfa
Route(config-isis-if-af)# commit
/*Configure Prefix-SID in ISIS and TI-LFA on P router */
Router# configure
Route(config)# router isis ring
Route(config-isis)# net 49.0001.1921.6800.1002.00
Route(config-isis)# segment-routing global-block 30100 39100
Route(config-isis)# nsr
Route(config-isis)# distribute link-state
Route(config-isis)# nsf cisco
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide
Route(config-isis-af)# mpls traffic-eng level-1
Route(config-isis-af)# mpls traffic-eng router-id loopback0
Route(config-isis-af)# segment-routing mpls
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 30102
Route(config-isis-af)# exit
!
Route(config-isis)# interface HundredGigE0/0/0/0
Route(config-isis-if)# circuit-type level-1
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# fast-reroute per-prefix
Route(config-isis-if-af)# fast-reroute per-prefix ti-lfa
Route(config-isis-if-af)# exit
!
Route(config-isis)# interface HundredGigE0/0/0/1
Route(config-isis-if)# circuit-type level-1
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# fast-reroute per-prefix
Route(config-isis-if-af)# fast-reroute per-prefix ti-lfa
Route(config-isis-if-af)# commit
/* Configure Prefix-SID in ISIS and TI-LFA on PE2 */
Router# configure
Route(config)# router isis ring
Route(config-isis)# net 49.0001.1921.6800.1003.00
Route(config-isis)# segment-routing global-block 30100 39100
Route(config-isis)# nsr
Route(config-isis)# distribute link-state
Route(config-isis)# nsf cisco
Route(config-isis)# address-family ipv4 unicast
Route(config-isis-af)# metric-style wide
Route(config-isis-af)# mpls traffic-eng level-1
Route(config-isis-af)# mpls traffic-eng router-id loopback0
Route(config-isis-af)# segment-routing mpls
Route(config-isis-af)# exit
!
Route(config-isis)# interface loopback0
Route(config-isis-if)# address-family ipv4 unicast
Route(config-isis-af)# prefix-sid index 30103
Route(config-isis-af)# exit
!
Route(config-isis)# interface HundredGigE0/0/0/1
Route(config-isis-if)# circuit-type level-1
Route(config-isis-if)# point-to-point
Route(config-isis-if)# hello-padding disable
Route(config-isis-if)# fast-reroute per-prefix
Route(config-isis-if-af)# fast-reroute per-prefix ti-lfa
Route(config-isis-if-af)# commit
Configure SR-TE for P and PE routers.
/Configure SR-TE on PE1 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# on-demand color 1
Router(config-sr-te-color)# dynamic mpls
Router(config-sr-te-color-dyn-mpls)# pcep
Router(config-sr-te-color-dyn-mpls)# exit
!
Router(config-sr-te)# on-demand color 2
Router(config-sr-te-color)# dynamic mpls
Router(config-sr-te-color-dyn-mpls)# pcep
Router(config-sr-te-color-dyn-mpls)# exit
!
Router(config-sr-te)# on-demand color 3
Router(config-sr-te-color)# dynamic mpls
Router(config-sr-te-color-dyn-mpls)# pcep
Router(config-sr-te-color-dyn-mpls)# commit
/*Configure SR-TE on P router */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# commit
/Configure SR-TE on PE2 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# on-demand color 11
Router(config-sr-te-color)# dynamic mpls
Router(config-sr-te-color-dyn-mpls)# pcep
Router(config-sr-te-color-dyn-mpls)# exit
!
Router(config-sr-te)# on-demand color 12
Router(config-sr-te-color)# dynamic mpls
Router(config-sr-te-color-dyn-mpls)# pcep
Router(config-sr-te-color-dyn-mpls)# exit
!
Router(config-sr-te)# on-demand color 13
Router(config-sr-te-color)# dynamic mpls
Router(config-sr-te-color-dyn-mpls)# pcep
Router(config-sr-te-color-dyn-mpls)# commit
Configure PCE on P router, and PCC on PE1 and PE2. Optionally, you can configure multiple PCEs as well.
/* Configure PCC on PE1 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# pcc
Router(config-sr-te-pcc)# source-address ipv4 205.1.0.1
Router(config-sr-te-pcc)# pce address ipv4 205.2.0.2
Router(config-sr-te-pcc)# commit
/* Configure PCE on P router */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# exit
Router(config)# pce
Router(config-pce)# address ipv4 205.2.0.2
Router(config-pce)# commit
/* Configure PCC on PE2 */
Router# configure
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# pcc
Router(config-sr-te-pcc)# source-address ipv4 205.3.0.3
Router(config-sr-te-pcc)# pce address ipv4 205.2.0.2
Router(config-sr-te-pcc)# commit
Configure SR colors on PE routers.
/* Define SR color on PE1 */
Router# configure
Router(config)# extcommunity-set opaque color1
Router(config-ext)# 1
Router(config-ext)# end-set
!
Router(config)# extcommunity-set opaque color2
Router(config-ext)# 2
Router(config-ext)# end-set
!
Router(config)# extcommunity-set opaque color3
Router(config-ext)# 3
Router(config-ext)# end-set
!
/* Define SR color on PE2 */
Router# configure
Router(config)# extcommunity-set opaque color11
Router(config-ext)# 11
Router(config-ext)# end-set
!
Router(config)# extcommunity-set opaque color12
Router(config-ext)# 12
Router(config-ext)# end-set
!
Router(config)# extcommunity-set opaque color13
Router(config-ext)# 13
Router(config-ext)# end-set
!
/* Configure EVPN route policy on PE1 */
Router# configure
Router(config)# route-policy evpn_odn_policy
Router(config-rpl)# if rd in (205.3.0.3:2) then
Router(config-rpl-if)# set extcommunity color color1
Router(config-rpl-if)# set next-hop 205.3.0.3
Router(config-rpl-if)# elseif rd in (205.3.0.3:3) then
Router(config-rpl-elseif)# set extcommunity color color2
Router(config-rpl-elseif)# set next-hop 205.3.0.3
Router(config-rpl-elseif)# elseif rd in (205.3.0.3:4) then
Router(config-rpl-elseif)# set extcommunity color color3
Router(config-rpl-elseif)# set next-hop 205.3.0.3
Router(config-rpl-elseif)# endif
Router(config-rpl)# pass
Router(config-rpl)# end-policy
/* Configure EVPN route policy on PE2 */
Router# configure
Router(config)# route-policy evpn_odn_policy
Router(config-rpl)# if rd in (205.1.0.1:2) then
Router(config-rpl-if)# set extcommunity color color11
Router(config-rpl-if)# set next-hop 205.1.0.1
Router(config-rpl-if)# elseif rd in (205.1.0.1:3) then
Router(config-rpl-elseif)# set extcommunity color color12
Router(config-rpl-elseif)# set next-hop 205.1.0.1
Router(config-rpl-elseif)# elseif rd in (205.1.0.1:4) then
Router(config-rpl-elseif)# set extcommunity color color13
Router(config-rpl-elseif)# set next-hop 205.1.0.1
Router(config-rpl-elseif)# endif
Router(config-rpl)# pass
Router(config-rpl)# end-policy
Configure BGP on PE1 and PE2.
/* Configure BGP on PE1 */
Router# configure
Router(config)# router bgp 100
Routerconfig-bgp)# bgp router-id 205.1.0.1
Routerconfig-bgp)# bgp graceful-restart
Router(config-bgp)# address-family l2vpn evpn
Router(config-bgp-af)# exit
!
Router(config-bgp)# neighbor 205.3.0.3
Router(config-bgp-nbr)# remote-as 100
Router(config-bgp-nbr)# update-source loopback 0
Router(config-bgp-nbr)# address-family l2vpn evpn
Router(config-bgp-nbr-af)# route-policy evpn_odn_policy in
Router(config-rpl)# commit
/* Configure BGP on PE2 */
Router# configure
Router(config)# router bgp 100
Routerconfig-bgp)# bgp router-id 205.3.0.3
Routerconfig-bgp)# bgp graceful-restart
Router(config-bgp)# address-family l2vpn evpn
Router(config-bgp-af)# exit
!
Router(config-bgp)# neighbor 205.1.0.1
Router(config-bgp-nbr)# remote-as 100
Router(config-bgp-nbr)# update-source loopback 0
Router(config-bgp-nbr)# address-family l2vpn evpn
Router(config-bgp-nbr-af)# route-policy evpn_odn_policy in
Router(config-rpl)# commit
Configure EVPN VPWS on PE1 and PE2.
/* Configure EVPN VPWS on PE1 */
Router# configure
Router(config)# interface GigE0/0/0/2.2 l2transport
Router(config-subif)# encapsulation dot1q 1
Router# exit
!
Router(config)# l2vpn
Router(config-l2vpn)# xconnect group evpn_vpws
Router(config-l2vpn-xc)# p2p e1_10
Router(config-l2vpn-xc-p2p)# interface GigE0/0/0/2.2
Router(config-l2vpn-xc-p2p)# neighbor evpn evi 2 target 10 source 10
Router(config-l2vpn-xc-p2p)#commit
/* Configure EVPN VPWS on PE2 */
Router# configure
Router(config)# interface GigE0/0/0/2.4 l2transport
Router(config-subif)# encapsulation dot1q 1
Router# exit
!
Router(config)# l2vpn
Router(config-l2vpn)# xconnect group evpn_vpws
Router(config-l2vpn-xc)# p2p e3_30
Router(config-l2vpn-xc-p2p)# interface GigE0/0/0/2.4
Router(config-l2vpn-xc-p2p)# neighbor evpn evi 2 target 10 source 10
Router(config-l2vpn-xc-p2p)#commit
/* Configure FXC on PE1 */
Router# configure
Router(config)# interface GigE0/0/0/2.3 l2transport
Router(config-subif)# encapsulation dot1q 3
Router# exit
!
Router(config)# l2vpn
Router(config-l2vpn)# flexible-xconnect-service vlan-unaware evpn_vu
Router(config-l2vpn-fxs-vu)# interface GigE0/0/0/2.3
Router(config-l2vpn-fxs-vu)# neighbor evpn evi 3 target 20
Router(config-l2vpn-fxs-vu)#commit
/* Configure FXC on PE2 */
Router# configure
Router(config)# interface GigE0/0/0/2.3 l2transport
Router(config-subif)# encapsulation dot1q 3
Router# exit
!
Router(config)# l2vpn
Router(config-l2vpn)# flexible-xconnect-service vlan-unaware evpn_vu
Router(config-l2vpn-fxs-vu)# interface GigE0/0/0/2.3
Router(config-l2vpn-fxs-vu)# neighbor evpn evi 3 target 20
Router(config-l2vpn-fxs-vu)#commit
/* Configure Prefix-SID in ISIS and TI-LFA */
PE1:
configure
router isis ring
net 49.0001.1921.6800.1001.00
segment-routing global-block 30100 39100
nsr
distribute link-state
nsf cisco
address-family ipv4 unicast
metric-style wide
mpls traffic-eng level-1
mpls traffic-eng router-id Loopback0
segment-routing mpls
!
interface Loopback0
address-family ipv4 unicast
prefix-sid index 30101
!
!
interface HundredGigE0/0/0/0
circuit-type level-1
point-to-point
hello-padding disable
address-family ipv4 unicast
fast-reroute per-prefix
fast-reroute per-prefix ti-lfa
!
!
P:
configure
router isis ring
net 49.0001.1921.6800.1002.00
segment-routing global-block 30100 39100
nsr
distribute link-state
nsf cisco
address-family ipv4 unicast
metric-style wide
mpls traffic-eng level-1
mpls traffic-eng router-id Loopback0
segment-routing mpls
!
interface Loopback0
address-family ipv4 unicast
prefix-sid index 30102
!
!
interface HundredGigE0/0/0/0
circuit-type level-1
point-to-point
hello-padding disable
address-family ipv4 unicast
fast-reroute per-prefix
fast-reroute per-prefix ti-lfa
!
!
interface HundredGigE0/0/0/1
circuit-type level-1
point-to-point
hello-padding disable
address-family ipv4 unicast
fast-reroute per-prefix
fast-reroute per-prefix ti-lfa
!
PE2:
configure
router isis ring
net 49.0001.1921.6800.1003.00
segment-routing global-block 30100 39100
nsr
distribute link-state
nsf cisco
address-family ipv4 unicast
metric-style wide
mpls traffic-eng level-1
mpls traffic-eng router-id Loopback0
segment-routing mpls
!
interface Loopback0
address-family ipv4 unicast
prefix-sid index 30103
!
!
interface HundredGigE0/0/0/1
circuit-type level-1
point-to-point
hello-padding disable
address-family ipv4 unicast
fast-reroute per-prefix
fast-reroute per-prefix ti-lfa
!
!
/* Configure SR-TE */
PE1:
configure
segment-routing
traffic-eng
on-demand color 1
dynamic mpls
pce
!
!
on-demand color 2
dynamic mpls
pce
!
!
!
on-demand color 3
dynamic mpls
pce
!
P:
configure
segment-routing
traffic-eng
!
PE2:
configure
segment-routing
traffic-eng
on-demand color 11
dynamic mpls
pce
!
!
on-demand color 12
dynamic mpls
pce
!
!
!
on-demand color 13
dynamic mpls
pce
!
/* Configure PCE and PCC */
PE1:
configure
segment-routing
traffic-eng
pcc
source-address ipv4 205.1.0.1
pce address ipv4 205.2.0.2
!
P:
configure
segment-routing
traffic-eng
pce
address ipv4 205.2.0.2
!
PE2:
configure
segment-routing
traffic-eng
pcc
source-address ipv4 205.3.0.3
pce address ipv4 205.2.0.2
!
/* Configure SR Color */
PE1:
configure
extcommunity-set opaque color1
1
end-set
!
extcommunity-set opaque color2
2
end-set
!
extcommunity-set opaque color3
3
end-set
!
PE2:
configure
extcommunity-set opaque color11
11
end-set
!
extcommunity-set opaque color12
12
end-set
!
extcommunity-set opaque color13
13
end-set
!
/* Configure EVPN route policy */
PE1:
configure
route-policy evpn_odn_policy
if rd in (205.3.0.3:2) then
set extcommunity color color1
set next-hop 205.3.0.3
elseif rd in (205.3.0.3:3) then
set extcommunity color color2
set next-hop 205.3.0.3
elseif rd in (205.3.0.3:4) then
set extcommunity color color3
set next-hop 205.3.0.3
endif
pass
end-policy
PE2:
configure
route-policy evpn_odn_policy
if rd in (205.1.0.1:2) then
set extcommunity color color11
set next-hop 205.1.0.1
elseif rd in (205.1.0.1:3) then
set extcommunity color color12
set next-hop 205.1.0.1
elseif rd in (205.1.0.1:4) then
set extcommunity color color13
set next-hop 205.1.0.1
endif
pass
end-policy
/* Configure BGP */
PE1:
configure
router bgp 100
bgp router-id 205.1.0.1
bgp graceful-restart
address-family l2vpn evpn
!
neighbor 205.3.0.3
remote-as 100
update-source Loopback0
address-family l2vpn evpn
route-policy evpn_odn_policy in
!
PE2:
configure
router bgp 100
bgp router-id 205.3.0.3
bgp graceful-restart
address-family l2vpn evpn
!
neighbor 205.1.0.1
remote-as 100
update-source Loopback0
address-family l2vpn evpn
route-policy evpn_odn_policy in
!
/* Configure EVPN VPWS */
PE1:
configure
interface GigE0/0/0/2.2 l2transport
encapsulation dot1q 1
!
l2vpn
xconnect group evpn_vpws
p2p e1_10
interface GigE0/0/0/2.2
neighbor evpn evi 2 target 10 source 10
!
!
PE2:
configure
interface GigE0/0/0/2.4 l2transport
encapsulation dot1q 1
!
l2vpn
xconnect group evpn_vpws
p2p e3_30
interface GigE0/0/0/2.4
neighbor evpn evi 2 target 10 source 10
!
!
!
/* Configure Flexible Cross-connect Service (FXC) */
PE1:
configure
interface GigE0/0/0/2.3 l2transport
encapsulation dot1q 3
!
l2vpn
flexible-xconnect-service vlan-unaware evpn_vu
interface GigE0/0/0/2.3
neighbor evpn evi 3 target 20
!
!
PE2:
configure
interface GigE0/0/0/2.3 l2transport
encapsulation dot1q 3
!
l2vpn
flexible-xconnect-service vlan-unaware evpn_vu
interface GigE0/0/0/2.3
neighbor evpn evi 3 target 20
!
!
Verify if SR-TE policy is auto-provisioned for each L2 service configured on EVPN ODN.
PE1# show segment-routing traffic-eng policy
SR-TE policy database
---------------------
Name: bgp_AP_1 (Color: 1, End-point: 205.3.0.3)
Status:
Admin: up Operational: up for 07:16:59 (since Oct 3 16:47:04.541)
Candidate-paths:
Preference 100:
Dynamic (pce 205.2.0.2) (active)
Weight: 0
30103 [Prefix-SID, 205.3.0.3]
Attributes:
Binding SID: 68007
Allocation mode: dynamic
State: Programmed
Policy selected: yes
Forward Class: 0
Distinguisher: 0
Auto-policy info:
Creator: BGP
IPv6 caps enable: no
PE1#show l2vpn xconnect group evpn_vpws xc-name evpn_vpws_1001 detail
Group evpn_vpws, XC evpn_vpws_1001, state is up; Interworking none
AC: Bundle-Ether12.1001, state is up
Type VLAN; Num Ranges: 1
Outer Tag: 1000
Rewrite Tags: []
VLAN ranges: [1, 1]
MTU 1500; XC ID 0xc0000018; interworking none
Statistics:
packets: received 642304, sent 642244
bytes: received 61661184, sent 61655424
drops: illegal VLAN 0, illegal length 0
EVPN: neighbor 20.20.20.20, PW ID: evi 1001, ac-id 10001, state is up ( established )
XC ID 0xa0000007
Encapsulation MPLS
Source address 10.10.10.10
Encap type Ethernet, control word enabled
Sequencing not set
Preferred path Active : SR TE pref_sid_to_PE3, On-Demand, fallback enabled
Tunnel : Up
Load Balance Hashing: src-dst-mac
PE1#show bgp l2vpn evpn route-type 1
BGP router identifier 205.1.0.1, local AS number 100
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0 RD version: 0
BGP main routing table version 36
BGP NSR Initial initsync version 25 (Reached)
BGP NSR/ISSU Sync-Group versions 36/0
BGP scan interval 60 secs
Status codes: s suppressed, d damped, h history, * valid, > best
i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 205.1.0.1:2 (default for vrf VPWS:2)
*>i[1][0000.0000.0000.0000.0000][1]/120
205.3.0.3 T:bgp_AP_1
100 0 i
PE1# show evpn evi ead detail
EVI Ethernet Segment Id EtherTag Nexthop Label SRTE IFH
----- ------------------------ -------- --------------------------------------- -------- ----------
2 0000.0000.0000.0000.0000 1 205.3.0.3 24000 0x5a0
Source: Remote, MPLS
adjacency-sid
index
prefix-sid
segment-routing
The applicable segment routing commands are described in the Segment Routing Command Reference for Cisco NCS 5500 Series Routers, Cisco NCS 540 Series Routers, and Cisco NCS 560 Series Routers.
Segment Routing (SR) is a flexible, scalable way of doing source routing. The source chooses a path and encodes it in the packet header as an ordered list of segments. Segments are identifier for any type of instruction. Each segment is identified by the segment ID (SID) consisting of a flat unsigned 32-bit integer. Segment instruction can be:
Go to node N using the shortest path
Go to node N over the shortest path to node M and then follow links Layer 1, Layer 2, and Layer 3
Apply service S
With segment routing, the network no longer needs to maintain a per-application and per-flow state. Instead, it obeys the forwarding instructions provided in the packet.
Segment Routing relies on a small number of extensions to Cisco Intermediate System-to-Intermediate System (IS-IS) and Open Shortest Path First (OSPF) protocols. It can operate with an MPLS (Multiprotocol Label Switching) or an IPv6 data plane, and it integrates with the rich multi service capabilities of MPLS, including Layer 3 VPN (L3VPN), Virtual Private Wire Service (VPWS), and Ethernet VPN (EVPN).
Segment routing can be directly applied to the Multiprotocol Label Switching (MPLS) architecture with no change in the forwarding plane. Segment routing utilizes the network bandwidth more effectively than traditional MPLS networks and offers lower latency. A segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels. The segment to process is on the top of the stack. The related label is popped from the stack, after the completion of a segment.
Segment Routing provides automatic traffic protection without any topological restrictions. The network protects traffic against link and node failures without requiring additional signaling in the network. Existing IP fast re-route (FRR) technology, in combination with the explicit routing capabilities in Segment Routing guarantees full protection coverage with optimum backup paths. Traffic protection does not impose any additional signaling requirements.
A router in a Segment Routing network is capable of selecting any path to forward traffic, whether it is explicit or Interior Gateway Protocol (IGP) shortest path. Segments represent subpaths that a router can combine to form a complete route to a network destination. Each segment has an identifier (Segment Identifier) that is distributed throughout the network using new IGP extensions. The extensions are equally applicable to IPv4 and IPv6 control planes. Unlike the case for traditional MPLS networks, routers in a Segment Router network do not require Label Distribution Protocol (LDP) and Resource Reservation Protocol - Traffic Engineering (RSVP-TE) to allocate or signal their segment identifiers and program their forwarding information.
SR-TE policy under "segment-routing traffic-eng" sub-mode
TE tunnel with SR option under "mpls traffic-eng" sub-mode
Note |
However, you can configure the above mentioned L2VPN and EVPN services using only "segment-routing traffic-eng" sub-mode. |
Each router (node) and each link (adjacency) has an associated segment identifier (SID). Node segment identifiers are globally unique and represent the shortest path to a router as determined by the IGP. The network administrator allocates a node ID to each router from a reserved block. On the other hand, an adjacency segment ID is locally significant and represents a specific adjacency, such as egress interface, to a neighboring router. Routers automatically generate adjacency identifiers outside of the reserved block of node IDs. In an MPLS network, a segment identifier is encoded as an MPLS label stack entry. Segment IDs direct the data along a specified path. There are two kinds of segment IDS:
Prefix SID: A segment ID that contains an IP address prefix calculated by an IGP in the service provider core network. Prefix SIDs are globally unique. A prefix segment represents the shortest path (as computed by IGP) to reach a specific prefix; a node segment is a special prefix segment that is bound to the loopback address of a node. It is advertised as an index into the node specific SR Global Block or SRGB.
Adjacency SID: A segment ID that contains an advertising router's adjacency to a neighbor. An adjacency SID is a link between two routers. Since the adjacency SID is relative to a specific router, it is locally unique.
A node segment can be a multi-hop path while an adjacency segment is a one-hop path.
Segment Routing Global Block (SRGB) is the range of labels reserved for segment routing. SRGB is local property of an segment routing node. In MPLS, architecture, SRGB is the set of local labels reserved for global segments. In segment routing, each node can be configured with a different SRGB value and hence the absolute SID value associated to an IGP Prefix Segment can change from node to node.
Router(config)# router isis 1
Router(config-isis)#segment-routing global-block 45000 55000
Feedback