The Routing Process Simplified
Until now, this chapter has examined discrete aspects of routing—specifically, peer negotiation and static versus dynamic routing. Before diving into details of routing configuration, it makes sense to pause here and briefly overview the BGP routing process in its entirety. BGP is a fairly simple protocol, which is why it's so flexible. Routes are exchanged between BGP peers via UPDATE messages. BGP routers receive the UPDATE messages, run some policies or filters over the ..
Instead of forming an infrastructure wireless LAN, the 802.11 standard allows users to optionally connect directly to each other in what is referred to as ad hoc mode, illustrated in Figure 22-3. The rationale behind this form of networking is to enable users to spontaneously set up wireless LANs. This optional mode is available to users on most radio cards. With ad hoc mode, there is no need for access points. The wireless connection is made directly between the users in a..
Processes of Link-State Protocols
The link-state protocols consist of four processes: Receive process The received information is processed, and then is given to the update process. The receive process does not make decisions—it simply forwards information to the two other processes. Update process Receives information from the receive process, processes the information received from all the neighbors, and creates information about the local router states. The updat..
IPsec Modes of Operation and Security Options
IPsec has many protocol options. This section provides a brief look at the main elements. One concept that's important to understand for IPsec is the concept of security associations, or SAs. An SA is simply a connection that provides security services to the traffic carried by it. When you use IPsec, you build SAs between the communicating devices. The SA contains information about which data traffic is going to be encrypted, how it is encrypted, whether and how it is authen..
Creating an Encrypted Router-to-Router VPN in a GRE Tunnel
There are several steps to these configurations, but they are the same on both routers. The first step is to create an appropriate key exchange policy using ISAKMP. The following set of commands defines the policy with priority 10. When ISAKMP negotiates the security association (SA) parameters, it starts with the lowest priority and goes to the highest. The highest possible priority value is 10,000: Router1(config)#crypto isakmp policy 10 Router1(config-isakmp)#encr aes 256..
