Enabling segment routeing in IGP like ISIS or OSPF is to replace the traditional LDP protocol in the access rings in the service provider environment, especially with the mobility transport core network. There are a lot of advantages in enabling SR-ISIS, as it has features like TI-LFA that is more robust in finding the alternate path when the actual path is down; no need to overload routers with enabling the MPLS protocol on top of IGP.
Let's explore how to enable segment routeing in the Nokia 7750 SR. I followed the Nokia documentation to enable the SR. Topology
Segment routing SR-ISIS configuration and verification in Nokia SROS
As part of the configuration, Area 10 is configured on PE1, PE2, PE5, PE6, ASBR1 and ASBR2.
1. Enabling ISIS with segment routeing.
Configure the MPLS label space for the SR to use and configure the index for each router or the label based on design.
router Base
mpls-labels
sr-labels start 20000 end 20099
exit
we have 2 options to configure the index in Nokia SROS, i configured in global so that i can use it for future case when using different areas in the topology. we have also option to configure under ISIS context.
segment-routing
sr-mpls
prefix-sids "system"
ipv4-sid index 11
exit
exit
exit
ISIS Configuration:
#--------------------------------------------------
echo "ISIS (Inst: 1) Configuration"
#--------------------------------------------------
isis 1
level-capability level-2
area-id 49.0001
traffic-engineering
traffic-engineering-options
advertise-delay
application-link-attributes
exit
exit
advertise-router-capability as
level 2
wide-metrics-only
exit
segment-routing
prefix-sid-range global
no shutdown
exit
Verification:
MPLS SRGB Block and Index advertisement in ISIS advertisement
Verifying the SR-ISIS prefix advertisement
Verifying the mpls table
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