MPLS NOTES\\
TODO
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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
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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**  

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MPLS FOR ARISTA:\\
Review limitations [[https://www.arista.com/en/um-eos/eos-bgpmpls-l3-vpn#xx1221179|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__
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  * 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 neighbord    # luk lesson 2.3
  show mpls ldp bindings     # luk lesson 2.3