User manual

Chapter 4 - Layer 3 Command Set - IP Networking OSPFv2 (Dynamic Routing Protocol Module)
Alvarion BreezeNET B130/B300 GigE 158 Operational User Manual
The value of the parameter is specified in seconds. "IP-address" defines
IP-address of a specific link, if you need to configure this particular link (optional
parameter). If this IP-address is not specified, the parameter will be applied to the
network interface. Note that in order to creating adjacency relationship between
two routers these parameters should be equal.
One of the routers connected to the network is automatically selected to be a
designated router (DR) judging by three parameters. If a link priority is specified
for the router it acts as a major criterion for DR selection. If priority is not set, only
router-id and IP-address affect the selection.
To set up router's priority for the interface one can using the following command
in config-if mode:
priority <0-255> [A.B.C.D]
Alike previously mentioned parameters, the priority can be set either to every link
on the interface individually or to the interface as a whole. The bigger the priority
the more chances this router has to become a designated router for this network.
If this parameter is set to zero, this router will never be selected as a designated
router.
OSPF protocol requires that Link-State databases of one area routers should be
identical. To do that routers exchange LSA information. In particular, transit
networks are used. In order to minimize network traffic, routers exchange their
LSA not directly with each other but using DR and Backup DR (BDR). BDR is
used for backing up DR in case of DR failure. BDR selection rules are identical to
DR selection rules. While Link-state database synchronization the routers
exchange database descriptions using master-slave relationship and broadcast
IP-packets. Each packet reception should be acknowledged. If acknowledge is not
received, initiating party makes a series of retransmits. OSPF administrator can
control periodicity of these retransmits for each interface and/or interface's links
in config-if mode:
retransmit-interval <3-65535> [A.B.C.D]
This retransmit interval is specified in seconds.
LSA exchange is performed in the following cases:
 start of the router or its connection to the network (link creation) after
selecting a network designated router
 after receiving LSA from any other area's router
 periodically after old database information expiration