All devices in this topology are configured to run SR with no LDP, with the exception of R5, which is LDP-only. This comparison looks at R4, which is configured to run SR and act as a mapping server so that those nodes that do not run LDP know what LFIB entry to install when forwarding traffic to R5’s loopback. This also highlights a key different between IOS-XE and IOS-XR Segment Routing capabilities in that IOS-XE does not support the configuration or forwarding of IPv6 Node-SIDs.
hostname R4 ! segment-routing mpls ! set-attributes address-family ipv4 sr-label-preferred exit-address-family ! global-block 16000 17999 ! connected-prefix-sid-map address-family ipv4 10.1.1.4/32 index 4 range 1 exit-address-family ! mapping-server ! prefix-sid-map address-family ipv4 10.1.1.5/32 index 5 range 1 exit-address-family ! ! ! interface Loopback5 ip address 10.1.1.4 255.255.255.255 ipv6 address 2001:1ab::4/128/128 ! interface GigabitEthernet1 description link to P7 ip address 10.4.7.4 255.255.255.0 ip router isis LAB ipv6 address 2001:1ab:4:7::4/64 ipv6 enable ipv6 router isis LAB mpls traffic-eng tunnels isis network point-to-point ! router isis LAB net 49.0100.1111.1111.0004.00 is-type level-2-only advertise passive-only metric-style wide log-adjacency-changes all segment-routing mpls segment-routing prefix-sid-map advertise-local passive-interface Loopback5 ! address-family ipv6 multi-topology advertise passive-only exit-address-family mpls traffic-eng router-id Loopback5 mpls traffic-eng level-2 !
hostname R4 ! interface Loopback0 ipv4 address 10.1.1.4 255.255.255.255 ipv6 address 2001:1ab::4/128 ! interface GigabitEthernet0/0/0/0 description link to R7 ipv4 address 10.4.7.4 255.255.255.0 ipv6 address 2001:1ab:4:7::4/64 ! ! router isis LAB is-type level-2-only net 49.0100.1111.1111.0004.00 log adjacency changes address-family ipv4 unicast metric-style wide advertise passive-only segment-routing mpls sr-prefer segment-routing prefix-sid-map advertise-local mpls ldp auto-config ! address-family ipv6 unicast metric-style wide advertise passive-only segment-routing mpls sr-prefer segment-routing prefix-sid-map advertise-local ! interface Loopback0 passive address-family ipv4 unicast prefix-sid absolute 17004 ! address-family ipv6 unicast prefix-sid absolute 17604 ! ! interface GigabitEthernet0/0/0/0 point-to-point address-family ipv4 unicast ! address-family ipv6 unicast ! ! ! segment-routing global-block 17000 23999 mapping-server prefix-sid-map address-family ipv4 10.1.1.5/32 5 range 1 ! address-family ipv6 2001:1ab::5/128 605 range 1 ! ! ! !