Zte ZXR10 5900E series Configuration Manual page 9

Here, "P" refers a router in the core of an operator network, which does not connect
to any router in any customer site, but is a part of MPLS L3 VPN tunnel. "P" supports
MPLS LSP or LDP function, but it does not need to support VPN.
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CE
CE refers to a router or switch connected to an operator network in a customer site.
Normally, IP router act as CE device.
VPN function is provided by PE routers, while P and CE routers do not have special
requirements for VPN configuration.
VPN-IPv4 Address and Route Distinguisher
Since L3 VPN may be connected to private networks through Internet and these private
networks can either use public or private addresses, the addresses used by different
private networks may be repeated when private networks use private addresses.
To avoid the repetition of private addresses, public addresses can be used by network
devices to replace private addresses. A solution is provided in RFC2547bis that uses an
existent private network ID to generate a definite new address.
The new address is a part of VPN-IPv4 address family, and it also is a BGP address family
of the MP-BGP protocol. In a VPN-IPv4 address, there is a value used to differentiate
different VPNs, called Route Distinguisher (RD).
The format of a VPN-IPv4 address is an eight-byte RD plus a four-byte IP address. RD is
the eight-byte value used for VPN differentiation. An RD consists of the following fields:
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Type field (two bytes): It determines the length of the other fields.
If the value of the type field is 0, Administrator (ADM) field covers two bytes and
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the Assignment Number (AN) field covers four bytes.
If the value of the type field is 1, ADM field covers four bytes and the Assignment
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Number (AN) domain covers two bytes.
If the value of the type field is 2, ADM field covers four bytes and the Assignment
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Number (AN) domain covers two bytes.
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ADM field: It identifies an administration assignment number
If the type domain is 0, the administrator domain contains an Autonomous System
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(AS) ID. RFC2547bis recommends a public AS ID allocated by Internet Assigned
Numbers Authority (IANA) be used (it is much better that the AS ID of the ISP or
customer itself is used).
If the value of the type field is 1, ADM field contains an IPv4 address. RFC2547bis
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recommends to use switch IP address (this address is normally configured as
switch ID). Router IP address is a public address.
If the type domain is 2, the administrator domain contain four bytes Autonomous
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System ID.
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AN field: The number assigned by a network operator
SJ-20150114102049-016|2015-03-10 (R1.0)
Chapter 1 MPLS L3VPN Configuration
1-3
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