Draytek Vigor 2960 series, User Manual

Page: 34 / 424

Vigor2960 Series User’s Guide 26
3
3
.
.
2
2
H
H
o
o
w
w
t
t
o
o
C
C
o
o
n
n
f
f
i
i
g
g
u
u
r
r
e
e
O
O
S
S
P
P
F
F
?
?
OSPF (Open Shortest Path First) uses the algorithm of SPF (Shortest Path First) to calculate
the route metric. It is suitable for large network and complicated data exchange. Both
Vigor3900 and Vigor2960 support up to OSPF version 2(only for IPv4).
The autonomous system (AS) used in OSPF indicates the largest entity and can be divided
into several
area s. Usually, Area 0 will be used as OSPF backbone which distributing the
routing information among areas.
When you need faster convergence than distance vector, want to support much larger
networks or want to have less susceptible to bad routing information, you can enable OSPF
feature to fit your request. Note that both routers must support OSPF function at the same
time to build the OSPF connection.
In the following example, a PC can go 192.168.2.0/24 and 192.168.4.0/24 without setting
any Static Route. Refer to the OSPF topology diagram listed below.
OSPF can place each router (e.g., Vigor3900A, Vigor3900B and Vigor2960 shown above) at
the root of a tree and calculate the shortest path to each destination according to the
cumulative cost to reach the destination.
Each router has its own view of the topology and calculates its own SPF tree, even though all
the routers build a shortest-path tree using the same link-state database.