Dell Force10 S4820T S4820T Configuration Guide - Page 693

• 3: connection to a stub network IP network/subnet number • 4: virtual link neighboring router ID LSA throttling LSA throttling provides configurable interval timers to improve OSPF convergence times. The default OSPF static timers (5 seconds for transmission, 1 second for acceptance) ensure sufficient time for sending and resending LSAs and for system acceptance of arriving LSAs. However, some networks may require reduced intervals for LSA transmission and acceptance. The throttling timers allow for this improved convergence times. The LSA throttling timers are configured in milliseconds, with the interval time increasing exponentially until a maximum time has been reached. If the maximum time is reached, the system, the system continues to transmit at the max-interval until twice the max-interval time has passed. At that point, the system reverts to the start-interval timer and the cycle begins again. When the LSA throttle timers are configured, syslog messages appear, indicating the interval times. Message 1 SYSLOG message for LSA transmit timer (45000 msec in this example) Mar 15 09:46:00: %STKUNIT0-M:CP %OSPF-4-LSA_BACKOFF: OSPF Process 10,Router lsa id 2.2.2.2 router-id 2.2.2.2 is backed off to transmit after 45000ms Message 2 SYSLOG message for L:SA arrival timer (1000 msec in this example) Mar 15 09:46:06: %STKUNIT0-M:CP %OSPF-4-LSA_BACKOFF: OSPF Process 10,Router lsa id 3.3.3.3 rtrid 3.3.3.3 received before 1000ms time Virtual Links In the case in which an area cannot be directly connected to Area 0, you must configure a virtual link between that area and Area 0. The two endpoints of a virtual link are ABRs, and the virtual link must be configured in both routers. The common non-backbone area to which the two routers belong is called a transit area. A virtual link specifies the transit area and the router ID of the other virtual endpoint (the other ABR). A Virtual Link cannot be configured through a Stub Area or NSSA. Router Priority and Cost Router priority and cost is the method the system uses to "rate" the routers. For example, if not assigned, the system will select the router with the highest priority as the DR. The second highest priority is the BDR. Priority is a numbered rating 0-255. The higher the number, the higher the priority. Cost is a numbered rating 1-65535. The higher the number, the greater the cost. The cost assigned reflects the cost should the router fail. When a router fails and the cost is assessed, a new priority number results. Open Shortest Path First (OSPFv2) | 693