BROCADE IP PRIMER

BI4XGBI24CT X RX T X RX T X RX T X RXBI4XGBI24CT X RX T X RX T X RX T X RXBI24C6 12 18 2430 36 42 48BI24CBigIron RX-8NETWORKS1 7 13 1925 31 37 43BI24CBI24CBI24CAC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMBI24CBI4XGBI4XGT X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RXEJECT SYSBI4XGBI4XGBI24CBI24CBI24C16T X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RX12BigIron RX-8NETWORKS7131819242530313637424348AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMBI24CBI24CBI24CBI24CBI24CBI4XGBI4XGT X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RXEJECT SYSBI4XGBI4XGBI24CBI24CBI24C16T X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RX12BigIron RX-8NETWORKS7131819242530313637424348AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMBI24CBI24CBI24CBI24CBI24CBI4XGBI4XGT X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RXEJECT SYSBI4XGBI4XGBI24CBI24CBI24C16T X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RX12BigIron RX-8NETWORKS7131819242530313637424348AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMBI24CBI24CBI24CBI24CBI24CBI4XGBI4XGT X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RXEJECT SYSBI4XGBI4XGBI24CBI24CBI24C16T X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RX12BigIron RX-8NETWORKS7131819242530313637424348AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMEJECT SYS AC OK DC OK ALMBI24CBI24CBI24CBI24CBI24CBI4XGBI4XGT X RX T X RX T X RX T X RXT X RX T X RX T X RX T X RXEJECT SYSChapter 11: Open Shortest Path First (OSPF)The priority is an eight-bit number (0-255) that can be configured on eachrouter. By default, this value is 1. If you configure the value to 0, that tells therouter (and its neighbors) that it will never take part in DR/BDR elections. Themain reason to do this is if you have a router whose resources (CPU, RAM, etc.)are limited. Being a DR or a BDR takes a fair amount of processing and RAM. Ifyou've got a very old router, you may want to make sure it never takes on thatrole. To do so, you would configure its priority to 0.The router with the highest priority wins the election, and becomes the DesignatedRouter. The router with the second highest priority becomes BDR.What if no priorities are configured? All the routers will have the same priority(default value is 1). The decision will then be made by looking at the router'sRouter ID. The Router ID is the IP address of the lowest-numbered loopbackinterface. If there are no loopback interfaces configured on the router, theRouter ID is the IP address of the lowest-numbered interface. When you havetwo or more routers with the same highest priority, the decision is made bywhich of those has the highest Router ID. The second-highest Router ID wouldbecome BDR.Priority 1Priority 5Priority 0Priority 100L1 - 1.2.3.4Priority 100L1 - 4.3.2.1BDRDRNeighbor StatesThe neighbors on a given router will go through six states on their way to fullybecoming synchronized with its routing table. The first three states arereferred to as the neighboring process. These are the states neighbors gothrough in order to establish themselves as neighbors.• Down. The router has not sent a Hello packet, nor has it received one• Init. A Hello packet has been sent to a neighbor, but no Hello packet hasbeen received from that neighbor• 2 Way. The router has sent a Hello packet to a neighbor, and hasreceived a Hello packet back; the reply will contain your router's Router IDinside; now, your router knows that the neighbor knows your router as well242 Brocade IP Primer