Alcatel-Lucent 7750 SR - IP Interworking VLL Datapath; Figure 43: IP Interworking VLL Datapath

Virtual Leased Line Services
7750 SR OS Services Guide Page 207
IP Interworking VLL Datapath
Figure 43: IP Interworking VLL Datapath
In order to be able to forward IP packets between CE 1 and CE 2 in Figure 43, PE 2 is manually
configured with both CE 1 and CE 2 IP addresses. These are host addresses and are entered in /32
format. PE 2 maintains an ARP cache context for each IP interworking VLL. PE 2 responds to
ARP request messages received on the Ethernet SAP. PE 2 responds with the Ethernet SAP
configured MAC address as a proxy for any ARP request for CE 1 IP address. PE 2 silently
discards any ARP request message received on the Ethernet SAP for an address other than that of
CE 1. Likewise, PE 2 silently discards any ARP request message with the source IP address other
than that of CE 2. In all cases, PE 2 keeps track of the association of IP to MAC addresses for ARP
requests it receives over the Ethernet SAP.
In order to forward unicast frames destined to CE 2, PE 2 needs to know CE 2 MAC address.
When the Ipipe SAP is first configured and administratively enabled, PE2 sends an ARP request
message for CE 2 MAC address over the Ethernet SAP. Until an ARP reply is received from CE2,
providing CE2's MAC address, unicast IP packets destined for CE2 will be discarded at PE2. IP
broadcast and IP multicast packets are sent on the Ethernet SAP using the broadcast or direct-
mapped multicast MAC address.
In order to forward unicast frames destined to CE 1, PE 2 validates the MAC destination address
of the received Ethernet frame. It should match that of the Ethernet SAP. It then removes the
Ethernet header and encapsulates the IP packet directly into a pseudowire without a control word.
PE 1 removes the pseudowire encapsulation and forwards the IP packet over the Frame Relay SAP
using RFC 2427, Multiprotocol Interconnect over Frame Relay, routed PDU encapsulation.
In order to forward unicast packets destined to CE1, PE2 validates the MAC destination address of
the received Ethernet frame. If the IP packet is unicast, the MAC destination must match that of
IP/MPLS
CE 2 [64.47.30.2/32]CE 1 [64.47.30.1/32]
CE 3 [64.47.31.1/32] CE 4 [64.47.31.2/32]
Ethernet/VLAN
SAP 1/1/1:1000
FR SAP
1/1/1:100
ATM SAP
2/1/1:0/100
Ethernet VLAN
SAP 3/1/1:1001
PE 1
PE 2
7750 SR
7750 SR
IPIPE_001
IP PW