3Com SuperStack 4 Configuration Manual page 140

152 C 6: IP R P O
HAPTER OUTING ROTOCOL PERATION
[Switch D-ospf-1]area 0
[Switch D-ospf-1-area-0.0.0.0]network 196.1.1.0 0.0.0.255
On Switch A, run the command to show the Switch's OSPF
display ospf peer
neighbors. Note that Switch A has three neighbors.
The status of each neighbor is full, which means that adjacency is set up between
Switch A and each neighbor. Switch A and Switch C should be set up with
adjacencies to all the routers on the network so that they can serve as the DR and
BDR on the network. Switch A is DR, while Switch C is BDR on the network. All
the other neighbors are DROthers (which means that they are neither DRs nor
BDRs).
5 Modify the priority of Switch B to 200:
[Switch B-Vlan-interface2000]ospf dr-priority 200
Execute the command on Switch A to show its OSPF
display ospf peer
neighbors. Please note the priority of Switch B has been modified to 200, but it is
still not the DR.
Only when the current DR is offline does the DR change. Shut down Switch A, and
run command on Switch D to display its neighbors. Note that
display ospf peer
the original BDR (Switch C) becomes the DR, and Switch B is the new BDR.
If all Ethernet Switches on the network are removed and added again, Switch B is
elected as the DR (with a priority of 200), and Switch A becomes the BDR (with a
priority of 100). Switching off and restarting all the switches initiates a new round
of DR and BDR selection.
Example: Configuring Networking requirements
OSPF Virtual Link
In Figure 34, Area 2 and Area 0 are not directly connected. Area 1 is used as the
transit area for connecting Area 2 and Area 0.