H3C Technologies H3C S7500E Series Switches - Manual (Page 59)

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The IP address specified as the LDP transport address must be the IP address of an interface on
the device.
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The remote peer IP address to be configured must be different from all existing remote peer IP
addresses.
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If a local adjacency exists between two peers, no remote adjacency can be established between
them. If a remote adjacency exists between two peers, you can configure a local adjacency for
them. However, the local adjacency can be established only when the transport address and
keepalive settings for the local peer and those for the remote peer match respectively, in which
case the remote adjacency will be removed. That is, only one remote session or local session can
exist between two LSRs, and the local session takes precedence over the remote session.
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By default, LDP does not advertise any prefix-based label mapping message through a remote
session, and remote sessions are used only to transfer messages for L2VPNs. For applications of
remote sessions, see information about Martini MPLS L2VPN configuration in MPLS L2VPN
Configuration of the MPLS Configuration Guide.
Configuring PHP
Follow these steps to configure PHP:
To do… Use the command… Remarks
Enter system view system-view —
Enter MPLS view mpls —
Specify the type of the label to be
distributed by the egress to the
penultimate hop
label advertise { explicit-null |
implicit-null | non-null }
Optional
By default, an egress distributes to
the penultimate hop an implicit null
label.
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For the S7500 series Ethernet switches, a label with a value of 0 can be at the top of a label stack.
After receiving a packet with such a label, the switch will pop the label directly and check whether
there is any inner layer label. If finding an inner layer label, the switch will forward the packet
based on the inner layer label; otherwise, the switch will forward the packet based on the IP
address.
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The device supports PHP when it works as a penultimate hop.
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For LDP sessions existing before the label advertise command is configured, you need to reset
the LDP sessions by using the reset mpls ldp command for the PHP configuration to take effect.