405
layer3 switches through link-state update (LSU) packages. Thus each layer3
switches receives LSAs from other layer3 switches, and all LSAs combined to
the link-state database.
2
）
Since a LSA is the description of the network topology structure around a layer3
switch, the LS database is the description of the network topology structure of
the whole network. The layer3 switches can easily create a weighted vector map
according to the LS database. Obviously, all layer3 switches in the same
autonomous system will have the same network topology map.
3
）
Each layer3 switch uses the shortest path finding (SPF) algorithm to calculate a
tree of shortest path rooted by itself. The tree provides the route to all the nodes
in the autonomous system, leaf nodes consist of the exterior route information.
The exterior route can be marked by the layer3 switch broadcast it, so that
additional information about the autonomous system can be recorded. As a
result, the route table of each layer3 switch is different.
OSPF protocol is developed by the IETF, the OSPF v2 widely used now is fulfilled
according to the content described in RFC2328.
13.6.2 OSPF Configuration Task List
The OSPF configuration for Edge-core series switches may be different from the
configuration procedure to switches of the other manufacturers. It is a two-step process:
1
、
Enable OSPF in the Global Mode;
2
、
Configure OSPF area for the interfaces.
The configuration task list is as follows:
1. Enable/disable OSPF protocol (required)
（
1
）
Enable/disable OSPF protocol (required)
（
2
）
Configure the ID number of the layer3 switch running OSPF (optional)
（
3
）
Configure the network scope for running OSPF (optional)
（
4
）
Configure the area for the interface (required)
2. Configure OSPF protocol parameters (optional)
（
1
）
Configure OSPF package sending mechanism parameters
1
）
Configure OSPF package verification
2
）
Set the OSPF interface to receive only
3
）
Configure the cost for sending packages from the interface
4
）
Configure OSPF package sending timer parameter (timer of broadcast interface
sending HELLO package to poll, timer of neighboring layer3 switch invalid
timeout, timer of LSA transmission delay and timer of LSA retransmission.
