BGP Messages and Neighbor States
The desired state for BGP neighbors is the established state. In that state, the routers have formed a TCP connection, and they have exchanged Open messages, with the parameter checks having passed. At this point, topology information can be exchanged using Update messages. Table 12-3 lists the BGP neighbor states, along with some of their characteristics. Note that if the IP addresses mismatch, the neighbors settle into an active state. Table 12-3 BGP Neighbor States
802.11 shared key authentication goes a step further than open system authentication by using the common WEP key to authenticate radio cards. This is a four-way handshaking process: 1. The radio card sends an authentication request. 2. The access point responds with an authentication frame containing challenge text, which is a string of unencrypted text. 3. The radio card encrypts the challenge text with the WEP key and sends the result to the access point. 4. The access ..
Case Study: Troubleshooting OSPF Neighbor Adjacencies
One of the various problems you often run into with OSPF is a pair of routers attached to the same network that will not become fully adjacent. If you know the right things to look for, you can quickly deal with this type of problem. Before troubleshooting neighbors that do not bring up an adjacency, though, you need to make certain they should become fully adjacent. For example, the routers in Figure 4-23 are connected to the same link, but they will never become fully adja..
Basic Foundation Identity Concepts
Almost all network-connected applications support some basic form of identity. Most often this takes the form of a username and a password. By proactively checking for bad passwords, educating users about choosing good passwords, and giving preference to applications with some form of secure transport (for example, Secure Shell [SSH]), you can achieve reasonable security for most systems. This chapter discusses more advanced identity systems that usually benefit very specific..
Cisco routers can watch the physical signals on an interface and trigger a backup interface if the primary link fails. The router will automatically drop the call after the primary circuit comes back up: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#interface Serial0/0 Router1(config-if)#backup delay 0 300 Router1(config-if)#backup interface BRI0/0 Router1(config-if)#encapsulation frame-relay Router1(config-if)..
