Dell PowerSwitch S4128F-ON OS10 Enterprise Edition User Guide Release 10.4.3.0 - Page 532

The LSA header is common to LSA types. Its size is 20 bytes. One of the fields of the LSA header is the link-state ID. Each router link is defined as one of four types-type 1, 2, 3, or 4. The LSA includes a link ID field that identifies the object this link connects to, by the network number and mask. Depending on the type, the link ID has different meanings. 1 Point-to-point connection to another router or neighboring router 2 Connection to a transit network IP address of the DR 3 Connection to a stub network IP network or subnet number 4 Virtual link neighboring router ID Router priority Router priority determines the designated router for the network. The default router priority is 1. When two routers attach to a network, both attempt to become the DR. The router with the higher router priority takes precedence. If there is a tie, the router with the higher router ID takes precedence. A router with a router priority set to zero cannot become the DR or BDR. If not assigned, the system selects the router with the highest priority as the DR. The second highest priority is the BDR. Priority rates from 0 to 255, with 255 as the highest number with the highest priority. OSPF route limit OS10 supports up to 16,000 OSPF routes. Within this range, the only restriction is on intra-area routes that scale only up to 1000 routes. Other OSPF routes can scale up to 16 K. Shortest path first throttling Use shortest path first (SPF) throttling to delay SPF calculations during periods of network instability. In an OSPF network, a topology change event triggers an SPF calculation that is performed after a start time. When the start timer finishes, a hold time can delay the next SPF calculation for an additional time. When the hold timer is running: • Each time a topology change occurs, the SPF calculation delays for double the configured hold time up to maximum wait time. 532 Layer 3