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MPLS NOTES
TODO

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.

Options:

Control plane: ipv4 / ipv6
Data plane: mpls or native ipv6

MPLS FOR ARISTA:
Review limitations here specially regarding next-hop-self in RR topologies.

!! PE CONFIGURATION

ip routing vrf BLUE
ip routing vrf RED
vrf instance RED
vrf instance BLUE
interface Ethernet4
   description pe1 -> c12
   mac-address 52:dc:ca:fe:03:04
   no switchport
   vrf BLUE
   ip address 10.1.12.1/24
!
router bgp 65000
   router-id 10.0.0.3
   bgp advertise-inactive
   neighbor 10.0.0.1 remote-as 65000
   neighbor 10.0.0.1 next-hop-self
   neighbor 10.0.0.1 update-source Loopback0
   neighbor 10.0.0.1 description rr1
   neighbor 10.0.0.1 send-community standard extended
   !
   address-family ipv4
      neighbor 10.0.0.1 activate
   !
   address-family vpn-ipv4
      neighbor 10.0.0.1 activate
      neighbor 10.0.0.1 encapsulation mpls next-hop-self source-interface Loopback0
   !
   vrf BLUE
      rd 1.1.1.1:200
      route-target import vpn-ipv4 200:0
      route-target export vpn-ipv4 200:0
      redistribute connected
      redistribute static
      redistribute ospf
   !
   vrf RED
      rd 1.1.1.1:100
      route-target import vpn-ipv4 100:0
      route-target export vpn-ipv4 100:0
      redistribute connected
      redistribute static
      redistribute ospf

!! P CONFIGURATION configure terminal

! note we don't need to enable ldp in each interface individually
interface Loopback0
mpls ip
mpls ldp
router-id interface Loopback0
no shutdown

!! ROUTE REFLECTOR:

router bgp 65000
   router-id 10.0.0.1
   bgp cluster-id 10.0.0.1
   bgp route-reflector preserve-attributes
   bgp advertise-inactive
   neighbor 10.0.0.2 remote-as 65000
   ! neighbor 10.0.0.2 next-hop-self
   neighbor 10.0.0.2 update-source Loopback0
   neighbor 10.0.0.2 description rr2
   neighbor 10.0.0.2 send-community standard extended
   !
   address-family ipv4
      neighbor 10.0.0.2 activate
   !
   address-family vpn-ipv4
      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
    10.0.0.2 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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MPLS SEGMENT ROUTING - SR-MPLS

Modes: shortest-path , explicit , PCE(controller)

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