Handling of Duplicate Link-Local IPv6 Addresses in FEC Resolution
Page 608 7450 ESS MPLS Guide
To avoid the automatic advertisement and resolution of IPv6 system FEC when the LDP session is
IPv4, the following procedure must be followed before and after the upgrade to the SR OS version
which introduces support of LDP IPv6.
1. Before the upgrade, implement a global prefix policy which rejects prefix [::0/0 longer] to
prevent IPv6 FECs from being installed after the upgrade.
2. In MISSU case:
→ If new IPv4 sessions are created on the node, the per-peer FEC-capabilities must be
configured to filter out IPv6 FECs.
→ Until an existing IPv4 session is flapped, FEC-capabilities have no effect on filtering
out IPv6 FECs, thus the import global policy must remain configured in place until the
session flaps. Alternatively, a per-peer-import-policy [::0/0 longer] can be associated
with this peer.
3. In cold upgrade case:
→ If new IPv4 sessions are created on the node, the per-peer FEC-capabilities must be
configured to filter out IPv6 FECs.
→ On older, pre-existing IPv4 sessions, the per-peer FEC-capabilities must be
configured to filter out IPv6 FECs.
4. When all LDP IPv4 sessions have dynamic capabilities enabled, with per-peer FEC-
capabilities for IPv6 FECs disabled, then the GLOBAL IMPORT policy can be removed.
Handling of Duplicate Link-Local IPv6 Addresses in FEC
Resolution
Link-local IPv6 addresses are scoped to a link and, as such, duplicate addresses can be used on
different links to the same or different peer LSR. When the duplicate addresses exist on the same
LAN, routing will detect them and block one of them. In all other cases, duplicate links are valid
because they are scoped to the local link.
In this section, LLn refers to Link-Local address (n).
FEC Resolution in LAN
---------(LL3)-[C]-(LL1)-----[E]
|
[Root LSR]-------[A]-(LL1)---[LAN] ----------[B]------
|
|
---------(LL2)-[D]------
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