Objectives
The simulator ticks each one as soon as the network meets it.
On every switch enable feature mpls segment-routing and, under router isis CORE → address-family ipv4 unicast, segment-routing mpls.
Map each Loopback0 to its SID: segment-routing → mpls → connected-prefix-sid-map → address-family ipv4 → 1.1.1.1/32 index 1 on PE1, and so on.
All five switches run SR and every loopback has its own SID (show isis segment-routing sids).
PE1 has label 16005 toward PE2 (show mpls switching), and P1 pops it (PHP).
PE1’s LSP to 5.5.5.5 uses segment routing; ping 5.5.5.5 from PE1.
Before you start
A prefix-SID is an index into the SR global block (SRGB, 16000–23999 by default), so the same label means the same destination on every switch. The switch before the owner pops the label, as LDP does. SR needs no label protocol: IS-IS carries the SIDs.
Concept
MPLS on NX-OS: a feature set, then features
NX-OS keeps MPLS behind a feature set, one step above ordinary features. The set is installed once and then enabled, and only then do feature mpls ldp, feature mpls traffic-engineering and feature mpls segment-routing exist. Each one in turn makes its own commands appear. The protocols themselves work as on any Cisco router: IS-IS carries the routes, TE data and SIDs, and labels are swapped hop by hop.
Concept
Segment routing: one label per destination, everywhere
With segment routing the IGP itself distributes labels. Each router gives its loopback a prefix-SID, an index into the SR global block (SRGB, 16000–23999 by default). Every SR router then reaches that loopback with the same label, 16000 + index. No LDP sessions are needed.
