Address And Fec Distribution - Alcatel-Lucent 7450 Manual

6 : MP2MP IPv6 forwarding
Each CapFlag appears no more than once in the TLV. If duplicates are found, the D-bit of the first
element is used. For forward compatibility, if the CapFlag is unknown, the receiver must silently
discard the element and continue processing the rest of the TLV.

Address and FEC Distribution

After an LDP LSR initializes the LDP session to the peer LSR and the session comes up, local
IPv4 and IPv6 interface addresses are exchanged using the Address and Address Withdraw
messages. Similarly, FECs are exchanged using Label Mapping messages.
By default, IPv6 address distribution is determined by whether the Dual-stack capability TLV,
which is defined in draft-ietf-mpls-ldp-ipv6, is present in the Hello message from the peer. This
coupling is introduced because of interoperability issues found with existing third-party LDP IPv4
implementations.
The following is the detailed behavior:
•
•
•
The above behavior applies to LDP IPv4 and IPv6 addresses and FECs. The procedure is
summarized in the flowchart diagrams in
7450 ESS MPLS Guide
If the peer sent the dual-stack capability TLV in the Hello message, then IPv6 local
addresses will be sent to the peer. The user can configure a new address export policy to
further restrict which local IPv6 interface addresses to send to the peer. If the peer
explicitly stated enabling of LDP IPv6 FEC type by including the IPv6 SAC TLV with the
D-bit (Disable-bit) set to 0 in the initialization message, then IPv6 FECs will be sent to the
peer. FEC prefix export policies can be used to restrict which LDP IPv6 FEC can be sent
to the peer.
If the peer sent the dual-stack capability TLV in the Hello message, but explicitly stated
disabling of LDP IPv6 FEC type by including the IPv6 SAC TLV with the D-bit (Disable-
bit) set to 1 in the initialization message, then IPv6 FECs will not be sent but IPv6 local
addresses will be sent to the peer. A CLI is provided to allow the configuration of an
address export policy to further restrict which local IPv6 interface addresses to send to the
peer. FEC prefix export policy has no effect because the peer explicitly requested
disabling the IPv6 FEC type advertisement.
If the peer did not send the dual-stack capability TLV in the Hello message, then no IPv6
addresses or IPv6 FECs will be sent to that peer, regardless of the presence or not of the
IPv6 SAC TLV in the initialization message. This case is added to prevent interoperability
issues with existing third-party LDP IPv4 implementations. The user can override this by
explicitly configuring an address export policy and a FEC export policy to select which
addresses and FECs to send to the peer.
Label Distribution Protocol
Figure 58 and Figure 59.
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