In a Synchronous Digital Hierarchy (SDH) based communications network
comprising a plurality of Intermediate Systems (IS), the IS being divided
between at least one IS--IS Area and at least one non-IS--IS Area, an
IS--IS Area being an area within which a routeing protocol forming part
of the Network Layer (Layer 3) of the Open Systems Interconnection
including routeing (OSI), is provided for routeing messages between
areas, a method is provided wherein static routes (Manual Adjacencies
(MA) are created at IS within the IS--IS Area to point to routes to a
group of one or more Network Equipments (NEs) within the non-IS--IS Area
and where a failure occurs in a link to or within a group and messages
from the IS--IS Area to the non-IS--IS Area are looped to the originating
IS--IS Area, identification of the NEs from which messages have been
looped are removed from the respective MAs allowing routeing of messages
via alternative MAs.