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--- network_stuff:arista:mpls [2022/05/18 09:56] – jotasandoku
+++ network_stuff:arista:mpls [2026/03/15 00:06] (current) – jotasandoku
@@ Line 2: / Line 2: @@
 TODO
 ----
-MPLS SEGMENT ROUTING NOTES (SR-MPLS NOTES)\\
+MPLS SEGMENT ROUTING NOTES (SRv6)
+\\
+think of SRv6–using IPv6 addresses as segment IDs, and breaking the least significant /64 to create microsids for service differentiation
+\\
 Is mostly MPLS but:
   * **labels** are distributed/encapsulated **in the IGP**
-  * labels are globally unique (not reused) so better control of the paths.
+  * labels are **globally unique** (not reused) so better control of the paths.
+Options:
+  * Control plane: ipv4 / ipv6
+  * Data plane: **mpls or native ipv6**
 ----
@@ Line 84: / Line 91: @@
         neighbor 10.0.0.3 activate
         neighbor 10.0.0.3 encapsulation mpls next-hop-self source-interface Loopback0
+----
+__IMPLICIT/EXPLICIT NULL__
+\\
+  * This null label is always 'sent' by the PE as signalling to the PHP.
+    * implicit null is no signalling and letting the PHP do its thing and send the mpls label as an IP packet (no labels) towards the PE
+    * explicit null is the PHP sending the mpls packet with the last label as a 'dummy' one (value 0(2 in IPv6)). The advantage is that EXP and QoS values are preserved.
+----
+SHOW COMMANDS:
+\\
+  show ip bgp vrf red
+  show ip route vrf red | begin Gateway
+  show mpls lfib route    # arista only labels for lo. You'll only see transport labels here
+  show bgp vpn-ipv4 172.16.0.0/24 detail # this is for the vpnv4 of the customer prefix 172
+  !
+  pe1#show bgp vpn-ipv4 172.16.2.0/24 detail
+  BGP routing table information for VRF default
+  Router identifier 10.0.0.1, local AS number 65000
+  BGP routing table entry for IPv4 prefix 172.16.2.0/24, Route Distinguisher: 65000:2
+   Paths: 1 available
+    Local
+.0.0.2 from 10.0.0.2 (10.0.0.2)
+        Origin IGP, metric -, localpref 100, weight 0, valid, internal, best
+        Extended Community: Route-Target-AS:65000:2
+        Remote MPLS label: 100001    <<< the vpnv4 label for 172.16.2.0/24
+  !
+  traceroute mpls ldp ip 10.0.0.1/32    # this shows the swapping of the transport label
+  show mpls ldp neighbor    # luk lesson 2.3
+  show mpls ldp bindings     # luk lesson 2.3
+----
+===MPLS SEGMENT ROUTING - SR-MPLS===
+== Modes: shortest-path , explicit , PCE(controller)==
+In the **shortest-path mode the label encodes the destination it stays __the same__ (the last router label) the entire journey. Eg: P2 router receives the last router's label (doesn't change) looks it up in its LFIB, finds "next hop toward the last router is P3, outgoing label (same label)", forwards it. Each P router has a LFIB that __has been synchronized via ISIS__ so they know what is the next hop as soon as they check the label**
+\\
+Configure explicit TE:
+  PE1
+  management te
+  mpls traffic-eng
+  router traffic-engineering
+     segment-routing
+        policy endpoint 10.0.0.6 color 100
+           name TO-PE2-EXPLICIT
+           binding-sid 1000100
+           path-group preference 100
+              segment-list label-stack 900007 900008 900009 900010 900006
+  route-map SET-COLOR-100 permit 10
+     set extcommunity color 100
+  router bgp 65001
+     neighbor 10.0.0.6 route-map SET-COLOR-100 in
+  show traffic-engineering segment-routing policy
+  Endpoint 10.0.0.6 Color 100, Name: TO-PE2-EXPLICIT, Counters: not available
+          Path group: State: active (for 00:02:05), modified: 00:02:05 ago
+                  Protocol: Static
+                  Originator: 0.0.0.0(AS0)
+                  Preference: 100
+                  IGP metric: 0 (static)
+                  Binding SID: 1000100
+                  Explicit null label policy: IPv6 (system default)
+                  Segment List: State: Valid, ID: 1, Counters: not available
+                  Protected: No, Reason: The top label is not protected
+                          Label Stack: [900007 900008 900009 900010 900006], Weight: 1
+                          Resolved Label Stack: [900008 900009 900010 900006], Next hop: 10.1.0.2, Interface: Ethernet1
+  show traffic-engineering segment-routing policy
+  show isis segment-routing prefix-segments
+  show ip route vrf t1 172.16.1.0/24 detail
+  <ios-xr commands>
+  show mpls forwarding labels <label>
+  show segment-routing traffic-eng  policy summary
+  show source-routing sr-te policy color 100 endpoint <IP> detail
+  show segment-routing traffic-eng  policy endpoint ipv4

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