This article explains SBFD with SR doesnt come up if loopback interface is not having 127.0.0.0/32 configured & instead we need to do its manually by configuring "reverse-path binding-label 1000990" to run bfd session on policy "ASR9903-01-MX10K3-01-GROUP11C-BASELINE" between cisco and MX10k3
Customer is having issue with SBFD being used with Segment routing only between MX10k & Cisco device however the same setup & configuration in between Cisco & MX960 device works fine. Customer is making the setup work by manually configuring below extra knobs on both ends to bring LSP up along SBFD session. Cisco lab-asr9903-01 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd reverse-path binding-label 1000999 Juniper lab-mx10k3-01 set protocols source-packet-routing source-routing-path MX10K3-01-ASR9903-01-GROUP11C-BASELINE binding-sid 1000999 +++++++++++++++++++Configs+++++++++++++++++ source-routing-path LAB-MX960-01-LAB-ASR9903-01-GROUP11C-UAE { to 10.10.11.52; lsp-external-controller pccd; primary { GROUP11-20 { bfd-liveness-detection { sbfd { remote-discriminator 168430388; } minimum-interval 3000; multiplier 3; no-router-alert-option; } } } } ++++++++MX10k Configs+++++++++++++++ source-routing-path LAB-MX10K3-01-LAB-ASR9903-01-GROUP12C-UAE { to 10.10.11.52; install 10.10.12.52; lsp-external-controller pccd; primary { GROUP12-20 { bfd-liveness-detection { sbfd { remote-discriminator 168430388; } minimum-interval 3000; multiplier 3; no-router-alert-option; } } The LSP wont come up between cisco and MX10k3 routers however it comes up with MX960. Lab-asr9903-01 --- lab-asr9k10-02 --- lab-crs3-02 --- lab-ncs6k-01 ---- lab-crs3-01 --- lab-mx960-01 Lab-asr9903-01 --- lab-asr9k10-02 --- lab-crs3-02 --- lab-mx10k3-01 The configuration between Cisco ASR9903 and Juniper MX10K3 should be applied to make the sBFD effective Cisco lab-asr9903-01 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd reverse-path binding-label 1000999 Juniper lab-mx10k3-01 set protocols source-packet-routing source-routing-path MX10K3-01-ASR9903-01-GROUP11C-BASELINE binding-sid 1000999 Customer make use of the loopback11 IP as the endpoint address of the device, lab-asr9903-01 is Router-A, where Router-B is 10.11.11.70. User@Router-B> show configuration protocols source-packet-routing source-routing-path MX10K3-01-ASR9903-01-GROUP11C-BASELINE to 10.11.11.52; binding-sid 1000999; lsp-external-controller pccd; primary { GROUP11-00 { bfd-liveness-detection { sbfd { remote-discriminator 168495924; } minimum-interval 3000; multiplier 3; no-router-alert-option; } } } 1. User@Router-A> show configuration protocols source-packet-routing source-routing-path MX960-01-ASR9903-01-GROUP11C-BASELINE to 10.11.11.52; lsp-external-controller pccd; primary { GROUP11-00 { bfd-liveness-detection { sbfd { remote-discriminator 168495924; } minimum-interval 3000; multiplier 3; no-router-alert-option; } } } 1. At router-A segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE color 11 end-point ipv4 10.11.11.70 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE max-install-standby-cpaths 1 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd minimum-interval 3000 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd multiplier 3 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd invalidation-action down segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd reverse-path segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd reverse-path binding-label 1000999 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd logging segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE bfd logging session-state-change segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 dynamic segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 dynamic metric segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 dynamic metric type te segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity include-all name GROUP11 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP08 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP20 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP21 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP30 segment-routing traffic-eng policy ASR9903-01-MX10K3-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP31 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE color 11 end-point ipv4 10.11.11.72 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE max-install-standby-cpaths 1 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE bfd segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE bfd minimum-interval 3000 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE bfd multiplier 3 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE bfd invalidation-action down segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE bfd logging segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE bfd logging session-state-change segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 dynamic segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 dynamic metric segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 dynamic metric type te segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 constraints segments protection protected-preferred segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity include-all name GROUP11 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP08 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP20 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP21 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP30 segment-routing traffic-eng policy ASR9903-01-MX960-01-GROUP11C-BASELINE candidate-paths preference 100 constraints affinity exclude-any name GROUP31 Customer confirmed that they could see that the sBFD packets are leaving the Cisco ASR but we were never seeing it on Mx10k.
Basically the issue was not a buggy behaviour but its an expected behaviour in junos as per the design.
SBFD initiator packets will use the router-alert option in the packets, which will allow the responder to process these packets without additional logic. However, other vendors do not support the presence of router-alert option in the packet, in such cases, a user configurable knob is available to disable addition of the router-alert in the BFD packets. However, this will require 127.0.0.1/32 address to be configured for the lo0 interface of the responder to allow processing these packets in the host path.