Introduction to Multicast VPN

Introduction to Multicast VPN


The new way refers to the setting up of Multipoint LSP in the MPLS VPN environment to carry multicast traffic in the VPN. Here, all CE routers belong to a single customer at different branches. There is no multicast receiver behind CE3 router. The MPLS core is PIM-free. Only PE routers will run PIM with the CE routers.

A separate function is required to enable IP multicast over a Multiprotocol Label Switching Virtual Private Networks (MPLS VPNs) network, as MPLS has no native ability to support it.

The Service Provider MVPN network forwards the customer IP multicast data to remote customer sites. To achieve this, customer traffic (C-packets) is encapsulated at the Service Provider PE inside P- packets. The encapsulated P-packet is then forwarded to remote PE sites as native multicast inside the P-Network.

During this process, the P-Network has no knowledge of the C-Network traffic. The PE is the device that participates in both networks. Note there may be more than one Customer Network per PE

PE routers configuration

The Loopback 0 interface of PE1 router is configured to be used as the Root Node IP address. The Opaque value for the multipoint LSP is constructed based on the VPN ID value of 1:1. The mdt default mpls mldp command creates the MP2MP LSP known to all PE routers for that particular VRF. This LSP is used to forward all customer multicast traffic by default.

Fig 1.1- Multicast VPN


Configuration on PE1 Router
!
ip vrf CUST1
 rd 1:1 vpn id 1:1                             
 route-target both 1:1 mdt default mpls mldp 1.1.1.1            
!
interface Loopback 0
 ip address 1.1.1.1 255.255.255.255
 ip ospf 1 area 0!ip multicast-routing vrf CUST1         
!ip pim vrf CUST1 rp-address 12.1.1.1
!
interface fastethernet 1/1
 ip vrf forwarding CUST1
 ip address 192.168.1.1 255.255.255.0 ip pim sparse-mode
!
router bgp 100
 neighbor 3.3.3.3 remote-as 100
 neighbor 3.3.3.3 update-source Loopback 0
 neighbor 4.4.4.4 remote-as 100
 neighbor 4.4.4.4 update-source Loopback 0
 !
 address-family vpnv4
 neighbor 3.3.3.3 activate
 neighbor 4.4.4.4 activate
 exit-address-family
 !
 address-family ipv4 vrf CUST1
 redistribute connected
 exit-address-family
!

The configuration of PE2 and PE3 is same as PE1 router.

Configuration on PE2 Router
!
ip vrf CUST1
 rd 1:1
 vpn id 1:1        
 route-target both 1:1
 mdt default mpls mldp 1.1.1.1          
!
interface Loopback 0
 ip address 3.3.3.3 255.255.255.255
 ip ospf 1 area 0!ip multicast-routing vrf CUST1        
!ip pim vrf CUST1 rp-address 12.1.1.1
!
interface fastethernet 1/1
 ip vrf forwarding CUST1
 ip address 192.168.2.1 255.255.255.0 ip pim sparse-mode
!
router bgp 100
 neighbor 1.1.1.1 remote-as 100
 neighbor 1.1.1.1 update-source Loopback 0
 neighbor 4.4.4.4 remote-as 100
 neighbor 4.4.4.4 update-source Loopback 0
 !
 address-family vpnv4
 neighbor 1.1.1.1 activate
 neighbor 4.4.4.4 activate
 exit-address-family
 !
 address-family ipv4 vrf CUST1
 redistribute connected
 exit-address-family
!

Configuration on PE3 Router
!
ip vrf CUST1
 rd 1:1
 vpn id 1:1        
 route-target both 1:1
 mdt default mpls mldp 1.1.1.1          
!
interface Loopback 0
 ip address 4.4.4.4 255.255.255.255
 ip ospf 1 area 0!ip multicast-routing vrf CUST1        
!ip pim vrf CUST1 rp-address 12.1.1.1
!
interface fastethernet 1/1
 ip vrf forwarding CUST1
 ip address 192.168.3.1 255.255.255.0 ip pim sparse-mode
!
router bgp 100
 neighbor 1.1.1.1 remote-as 100
 neighbor 1.1.1.1 update-source Loopback 0
 neighbor 3.3.3.3 remote-as 100
 neighbor 3.3.3.3 update-source Loopback 0
 !
 address-family vpnv4
 neighbor 1.1.1.1 activate
 neighbor 3.3.3.3 activate
 exit-address-family
 !
 address-family ipv4 vrf CUST1
 redistribute connected
 exit-address-family
!

No multicast traffic is sent by CE routers at this stage.