Using the default-information originate Command
OSPF does not support redistribution of statically defined default routes. Instead, OSPF requires the default-information originate router subcommand, which essentially tells OSPF tore distribute any default routes found in the routing table, either static routes or routes from another routing protocol. The following list summarizes the default routing features when using the default-information originate command with OSPF: ■ Redistributes any default route (0.0.0.0/0) in ..
RIP Convergence When Routing Updates Cease
When a router ceases to receive routing updates, RIP must wait for some timers to expire before it decides that routes previously learned from the now-silent router can be considered to be failed routes. To deal with such cases, RIP uses its Invalid, Flush, and Holddown timers to prevent loops. Coincidentally, RIP’s convergence time increases to several minutes as a result. Example 8-3 details just such a case, where R1 simply ceases to hear RIP updates from R3. (To create..
Converging to a New STP Topology
STP logic monitors the normal ongoing Hello process when the network topology is stable; when the Hello process changes, STP then needs to react and converge to a new STP topology. When STP has a stable topology, the following occurs: 1. The root switch generates a Hello regularly based on the Hello timer. 2. Each non-root switch regularly (based on the Hello timer) receives a copy of the root’s Hello on its RP. 3. Each switch updates and forwards the Hello out its Desi..
With ad hoc wireless LANs, there are no access points; therefore, the radio cards must send beacons. The ad hoc mode of operation transpires as follows: 1. After a user switches to ad hoc mode, the radio card begins sending beacons if one is not received within a specific period of time. 2. After receiving a beacon, each radio card waits a random period of time. 3. If a beacon is not heard from another station in this time, then the station sends a beacon. The random wait ..
Strive for Operational Simplicity
Network designers make decisions regarding operational complexity every day. Most don't call it that, though; they tend to think along the lines of the difficulty and burden that specific technology places on administrators or users. This section gets to a key aspect of your network security system: achieving operational simplicity can mean the difference between a security system that works for you and a security system that you work for. Some hard and soft metrics to measu..
