Avaya ERS 8600 series, Configuration Manual

Page: 36 / 420

adding the black hole route a check is made to ensure that no other static route to that identical
destination in an enabled state exists. If such a route exists, you cannot add the black hole
route, and the system generates an error message.
However, if an enabled-black hole route exists, you cannot add another static route to that
destination. You must first delete or disable the black hole route before you can add a regular
static route to that destination.
Open Shortest Path First protocol
Open Shortest Path First (OSPF) protocol is an Interior Gateway Protocol (IGP) that distributes
routing information between routers belonging to a single autonomous system (AS). OSPF is a
link-state protocol intended for use in large networks.
This section contains the following topics:
• Overview on page 36
• Benefits on page 37
• Autonomous system and areas on page 37
• Neighbors on page 38
• OSPF routers on page 40
• Router types on page 40
• OSPF interfaces on page 41
• OSPF and IP on page 43
• OSPF packets on page 43
• Link-state advertisements on page 44
• AS external routes on page 45
• OSPF virtual links on page 45
• OSPF routing algorithm on page 46
• Specifying ASBRs on page 46
Overview
In an OSPF network, each router maintains a link-state database that describes the topology of
the autonomous system (AS). The database contains the local state for each router in the AS,
including usable interfaces and reachable neighbors. If the router detects changes, it shares
them by flooding link-state advertisements (LSAs) throughout the AS. Routers synchronize
topological databases based on shared information from LSAs.
IPv6 routing fundamentals
36 Configuration — IPv6 Routing November 2010