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Cisco 10000 Series Router Software Configuration Guide
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Chapter 4 Configuring Multiprotocol Label Switching
Half-Duplex VRF
The Cisco 10000 series router redistributes routes from the downstream VRF into Multiprotocol Border
Gateway Protocol (MP-BGP). The spoke PE router typically advertises a summary route across the
MPLS core for the connected spokes. The upstream VRF configured on the hub PE router imports the
advertised summary route.
Reverse Path Forwarding Check Support
Reverse Path Forwarding (RPF) check ensures that an IP packet entered the router using the correct
inbound interface. The HDVRF feature supports unicast RPF check on the spoke-side interfaces.
Because different VRFs are used for downstream and upstream forwarding, HDVRF extends the RPF
mechanism to ensure that source address checks occur in the downstream VRF.
Feature History for Half-Duplex VRF
Restrictions for Half-Duplex VRF
The Half-Duplex VRF feature has the following restrictions:
• In both the upstream and downstream VRFs, routing protocols are not supported on interfaces
configured for half-duplex VRFs.
• Half-duplex VRFs apply only to virtual access interfaces (VAIs) and virtual template interfaces.
Only IP unnumbered interfaces are supported.
• It is not supported with Routing with Bridged Encapsulation (RBE).
Prerequisites for Half-Duplex VRF
The Half-Duplex VRF feature has the following requirements:
• The spoke PE routers must be running Cisco IOS Release 12.2(16)BX2, Cisco IOS Release
12.3(7)XI1, or a later release.
• The performance routing engine (PRE), part number ESR-PRE2, must be installed in the router’s
chassis.
Cisco IOS Release Description Required PRE
12.2(16)BX2 This feature was introduced on the Cisco 10000 series
router.
PRE2
12.3(7)XI1 This feature was integrated into Cisco IOS Release
12.3(7)XI1.
PRE2
12.2(28)SB This feature was integrated into Cisco IOS Release
12.2(28)SB.
PRE2
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