dokucama

This is an old revision of the document!

---

MPLS NOTES
TODO

---

MPLS SEGMENT ROUTING NOTES (SR-MPLS NOTES)
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 neighbord    # luk lesson 2.3
show mpls ldp bindings     # luk lesson 2.3