HPE FlexNetwork 5510 HI Series, Руководство по настройке Mpls

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MPLS forwarding
Figure 5 MPLS forwarding
As shown in Figure 5 , a packet is forwarded over the MPLS network in the following steps:
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 VLAN-interface 20 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 VLAN-interface 30 to the next hop
LSR Router D.
3. When receiving the labeled packet, Router D (the egress) 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 VLAN-interface 40 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).
Router A
Router B
Ingress
Router C
Router D
Egress
Router E
Router F
IP:10.1.1.1
MPLS network
IP:10.1.1.1 40 IP:10.1.1.1 50 IP:10.1.1.1
Vlan10 Vlan20 Vlan20 Vlan30 Vlan30 Vlan40
FIB table
LFIB table
LFIB table
Nexthop Dest Out int Out label
10.1.0.0 Vlan20 40 Router C
Nexthop
Router D
Out int
Vlan30
Out label
50
Oper
Swap
In label
40
Nexthop
Router E
Out int
Vlan40
Out label
--
Oper
Pop
In label
50