Mpls Forwarding; Php - HP HPE FlexNetwork MSR Router Series Configuration Manual

MPLS forwarding

Figure 5 MPLS forwarding
Dest Out label
40
10.1.0.0
Router A
As shown in
1. Router B (the ingress LSR) receives a packet with no label. Then, it performs the following
operations:
a. Identifies the FIB entry that matches the destination address of the packet.
b. Adds the outgoing label (40, in this example) to the packet.
c. Forwards the labeled packet out of the interface GigabitEthernet 2/0/2 to the next hop LSR
Router C.
2. When receiving the labeled packet, Router C processes the packet as follows:
a. Identifies the LFIB entry that has an incoming label of 40.
b. Uses the outgoing label 50 of the entry to replace label 40 in the packet.
c. Forwards the labeled packet out of the outgoing interface GigabitEthernet 2/0/2 to the next
hop LSR Router D.
3. When receiving the labeled packet, Router D (the egress LSR) processes the packet as follows:
a. Identifies the LFIB entry that has an incoming label of 50.
b. Removes the label from the packet.
c. Forwards the packet out of the outgoing interface GigabitEthernet 2/0/2 to the next hop LSR
Router E.
If the LFIB entry records no outgoing interface or next hop information, Router D performs the
following operations:
a. Identifies the FIB entry by the IP header.
b. Forwards the packet according to the FIB entry.

PHP

An egress node must perform two forwarding table lookups to forward a packet:
•
Two LFIB lookups (if the packet has more than one label).
FIB table
Nexthop Out int
GE2/0/2
Router C
In label
40
IP:10.1.1.1 40
GE2/0/1 GE2/0/2
Router B
Ingress
Figure 5, a packet is forwarded over the MPLS network as follows:
LFIB table
Oper Out label Nexthop
Swap 50
Router D
IP:10.1.1.1 50 IP:10.1.1.1
GE2/0/1 GE2/0/1
GE2/0/2
Router C
Router F
4
LFIB table
In label Oper Out label
50 Pop --
Out int
GE2/0/2
IP:10.1.1.1
GE2/0/2
Router D
Egress
MPLS network
Nexthop Out int
GE2/0/2
Router E
Router E