Injecting Information Statically into BGP
Listing prefixes with the network command has the same drawbacks as dynamic redistribution. If a route that is listed with the network command goes down, BGP will send an update; if the route comes back, BGP will send another update. If this behavior continues, the IGP instability will translate into BGP instabilities. The only way around this is to use a combination of statically defined prefixes in conjunction with the network command. This will ensure that the prefixes w..
The Database Description Packet
The database description (DBD) packet, which is OSPF packet type 2, is sent after routers have listed each other in their hello packets, and after two-way communication has been established. This is the initialization of adjacency. DBD packets describe the contents of link-state databases; describing the entire database requires that multiple packets be sent. During the database-exchange process, one router is elected as master and the other as slave. The master..
The development of routers can be characterized through three generations. The first generation consists of a single CPU controlling relatively unsophisticated line cards through a general- purpose shared I/O bus. Packet queues between line cards are maintained in central or shared memory by the CPU, which coordinates all packet forwarding. In the worst case, packets may traverse the I/O bus twice to complete the forwarding process. A second-generation switch su..
Cisco Router and Security Device Manager
Cisco Router and Security Device Manager (SDM) is an intuitive, secure, web-based embedded device manager of Cisco IOSenabled devices. SDM provides intelligent wizards, detects mis-configured devices, steps security managers through firewall and VPN configurations, and has been certified and recommended by some key organizations within Cisco, such as the Cisco Network Supported Accounts (NSA), a group of expert engineers within Cisco whose services are sold to high-end client..
Recall that the traditional STP offers the PortFast feature, in which switch ports are allowed to immediately enter the Forwarding state as soon as the link comes up. Normally, PortFast provides quick network access to end-user devices, where bridging loops never are expected to form. Even while PortFast is enabled on a port, STP still is running and can detect a bridging loop. However, a loop can be detected only in a finite amount of time— the length of time require..
