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
Defaults Inside the AS: Primary/Backup BGP Policy
Consider the routing scenario shown in Figure 8-2. AS1 is connected to the Internet via twoconnections. RTC in SF is running Exterior Border Gateway Protocol (EBGP) with oneprovider, whereas RTD in NY is running EBGP with another provider. Inside the AS, RTCand RTD are running IBGP; however, they are not physically connected. As a result, trafficbetween RTC and RTD must flow through routers RTA and RTB. Figure 8-2. Following Defaults: Loop Situation Assume that RTC a..
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 ..
Integrated Services Digital Network (ISDN) is used by telephone companies to carry digitized voice and data over the existing telephone system. ISDN has emerged as one of the leading technologies for telecommuting and remote office connection into the corporate headquarters. On the seven layer model, ISDN operates at the physical, data link, and network layers. ISDN basic rate interface (BRI) provides two barrier channels (commonly referred as B channels). Each of these B ch..
GP/MPLS Graceful Restart Operation
This section describes the operation of the BGP with an MPLS graceful restart mechanism using the network shown in Figure 7-11. The following discussion assumes that LSR1 and LSR2 are capable of both BGP with MPLS graceful restart and NSF. The following sequence of steps does not necessarily indicate the processing steps of a specific implementation. This description is intended to provide a functional view. • During BGP session establishment, LSR1 and LS..
