Juniper JUNOSE 11.2.X BGP AND MPLS, Руководство по настройке

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When IP packets arrive at the ingress LER, they are looked up in the relevant IP forwarding
table and then are forwarded into an LSP. Every IP route eventually points to an IP
interface. The IP interface contains IP attributes that affect how the IP packet is forwarded.
IPv4 routes point only to IPv4 interfaces and IPv6 routes point only to IPv6 interfaces.
Because IP routes cannot point directly to MPLS major interfaces, MPLS automatically
creates up to four dynamic IP shared interfaces that are stacked on each MPLS major
interface. When you issue the
mpls command in Interface Configuration mode, the
interfaces are created dynamically and provide the interfaces an IP route needs to point
to. You can specify a profile (created with the
profile command) to configure attributes
for these interfaces with the mpls create-dynamic-interfaces command. You can use
the same command to enable or disable the creation of specific interface types or all
types.
Each dynamic interface is one of the following types:
•
By default, MPLS creates one dynamic IPv4 interface per MPLS major interface for
non-VPN traffic. This interface is used by default for VPN traffic as well.
• By default, but only if IPv6 is enabled in the virtual router, MPLS creates one dynamic
IPv6 interface per MPLS major interface for non-VPN traffic. This interface is used by
default for VPN traffic as well.
•
If you configure it to do so, MPLS creates one dynamic IPv4 interface per MPLS major
interface for VPN traffic. If this interface is not created, then the VPN traffic uses the
default IPv4 interface for non-VPN traffic.
Typically, you request the creation of separate IPv4 interfaces for VPN traffic only when
you want the IPv4 interface for VPN traffic to have different attributes, such as a
different IP policy, from the IPv4 interface for non-VPN traffic. When it is acceptable
for the VPN traffic and the non-VPN traffic to receive the same IP treatment, then you
do not need to create separate IPv4 interfaces for the VPN traffic.
•
If you configure it to do so, but only if IPv6 is enabled in the virtual router, MPLS creates
one dynamic IPv6 interface per MPLS major interface for VPN traffic. If this interface
is not created, then the VPN traffic uses the default IPv6 interface for non-VPN traffic.
Typically, you request the creation of separate IPv6 interfaces for VPN traffic only
when you want the IPv6 interface for VPN traffic to have different attributes, such as
a different IP policy, from the IPv6 interface for non-VPN traffic. When it is acceptable
for the VPN traffic and the non-VPN traffic to receive the same IP treatment, then you
do not need to create separate IPv6 interfaces for the VPN traffic.
IPv6 must be enabled in the parent virtual router so that IPv6 dynamic interfaces can be
created over MPLS interfaces. Otherwise, IPv6 VPNs do not work correctly,
All VPN traffic sent onto or received from the same layer 2 interface uses the same IPv4
VPN or IPv6 VPN interface. Consequently, any policy attached to the interface applies
to all that VPN traffic.
Related Topics TTL Processing in the Platform Label Space Overview on page 222
•
•
IP Data Packet Mapping onto MPLS LSPs Overview on page 229
Copyright © 2010, Juniper Networks, Inc. 230
JunosE 11.2.x BGP and MPLS Configuration Guide