Juniper JUNOSE, Руководство по настройке

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Each LSP is unidirectional for data traffic, so you must establish LSPs in both directions
for two-way data transport. Figure 74 on page 386 shows that two LSPs have been
created between PE 1 and PE 2. PE 1 and PE 2 have an MP-BGP session as shown
previously in Figure 73 on page 384.
Figure 74: LSP Creation for BGP/MPLS VPN
The PE 1–PE 2 LSP carries traffic only from PE 1 to PE 2, using label 21 for the PE
1 to P 1 link, label 19 for the P 1 to P 2 link, and label 46 for the P 2 to PE 2 link. PE
1 can forward data packets along the LSP to PE 2 and its customer sites.
Similarly, the PE 2–PE 1 LSP carries traffic only from PE 2 to PE 1, using label 58
for the PE 2 to P 2 link, label 12 for the P 2 to P 1 link, and label 37 for the P 1 to
PE 1 link. PE 2 can forward data packets along the LSP to PE 1 and its customer
sites.
Example: Data Transport
The process of data transport is shown in Figure 75 on page 387. PE 1 has already
received announcements from PE 2; an LSP has been established between PE 1 and
PE 2.
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Transporting Packets Across an IP Backbone with MPLS
JUNOSe 11.0.x BGP and MPLS Configuration Guide