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Introduction | 37
Aprisa LTE User Manual 2.1
OSPF
OSPF (Open Shortest Path First) is a standardize Interior Gateway Protocol (IGP) and commonly used in large
enterprise networks. OSPF is a link-state routing protocol providing fast convergence and excellent
scalability. As a link-state protocols, OSPF is very efficient in its use of network bandwidth. It realizes the
Link State routes and distribute routing information in an area.
OSPF introduce the following benefits:
✓ OSPF is loop free (derived by its own algorithm) and scalable supporting high number of routers in
an AS.
✓ OSPF protocol design to minimize the traffic overhead and ensures a better use of bandwidth by
sending updates only in case routing changes occur instead of periodically, uses short multicast hello
message (for discovery and n
eighbours’ maintenance), multicast instead of broadcast, minimize
route exchange, NSSA (not-so-stubby area) concept to reduce route injection into extension of stub
area, and ABRs (Area Border Routers) route aggregation to reduce route info.
✓ OSPF providing fast convergence time since routing changes are propagated instantaneously in short
time and not periodically.
✓ OSPF allows load balancing.
✓
OSPF allows the concept of logical area division of networks where routers can be divided into areas
in an Autonomous System (AS) to limit link state advertise updates over the whole network/AS. This
also provides a mechanism for aggregating routes and summary of routing information between
regions and cutting down on the unnecessary propagation of subnet information.
✓ OSPF supports routing authentication by using password and MD5 authentication.
✓
OSPF interoperable with BGP and IGP routing protocols, allowing external routes injection and keeps
their tracks.
More Information on DMVPN, BGP, OSPF Setup Applications
For more information on setting up basic BGP network, DMVPN network, DMVPN behind NAT network, DMVPN
over BGP network, basic OSPF network, and DMVPN over OSPF network see the
‘ Aprisa LTE Dynamic Routing
Protocols ’ network configuration guide.