NEXT_HOP Behavior Over Nonbroadcast Multiaccess Media
Media such as Frame Relay and ATM are referred to as nonbroadcast multiaccess media. Themany-to-many direct interaction between routers is not guaranteed unless virtual circuits areconfigured from each router to all other routers. This is referred to as a full-mesh topology,and it is not always implemented for a number of reasons. In practice, Frame Relay or ATMvirtual circuits are provided by the access carrier at a certain dollar amount per circuit, andadditional circuits t..
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 ..
The following list describes the process that occurs when a radio card uses passive scanning: 1. The radio card automatically tunes to each RF channel, listens for a period of time, and records information it finds regarding access points on each channel. 2. 2. By default, each access point transmits a beacon frame every 100 milliseconds on a specific RF channel, which the administrator configures. 3. While tuned to a specific channel, t..
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..
Your Service Provider Doesn't Do What You Want
Some service providers support only a limited range of MPLS features. The most common missing features are specific routing protocols for PE-CE routing and multicast support. This example will assume that you want to pass OSPF and multicast through an MPLS network that supports only BGP: Router-CE-A1#configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router-CE-A1(config)#ip multicast-routingRouter-CE-A1(config)#interface FastEthernet0/0.1Route..
