KEEPALIVE messages are comprised only of the 19-byte BGP message header shown in Figure 11-3. These are exchanged whenever an update-free period exceeds the holdtime negotiated in the OPEN message exchange. A KEEPALIVE is also sent to acknowledge the OPEN message before moving from the OPEN_SENT to ESTABLISHED session state. If the holdtime is zero, KEEPALIVE messages are not sent, except to acknowledge an OPEN. TIP The minimum keepalive period is ..
Mitigating the Detrimental Effects of BGP with MPLS Restart
you learned that the BGP graceful restart mechanism allows a speaker to announce its capability to preserve the BGP-related IP forwarding state across the BGP restart. The BGP with the MPLS graceful restart mechanism[5] extends the BGP graceful restart procedure to MPLS. In essence, during the establishment of the pre-restart BGP session, an LSR informs its peers about its capability to preserve the MPLS forwarding state across the BGP restart. When the LSR restarts, its pee..
Cisco Unified Wireless Network Architecture
Cisco has collected a complete set of functions that are integral to wireless LANs and called them the Cisco Unified Wireless Network. This new architecture offers the follow ing capabilities, which are centralized so that they affect wireless LAN devices located anywhere in the network: ■ WLAN security ■ WLAN deployment ■ WLAN management ■ WLAN control To centralize these aspects of a WLAN, many of the functions found within autonomous APs have to be shifted toward ..
This section looks at an advanced queuing feature for Frame Relay known as CBWFQ. CBWFQ is essentially an extension of the original flow-based WFQ algorithm discussed .In contrast to WFQ, CBWFQ allows and supports up to 64 user-defined traffic classes. Figure 18-2 illustrates the basic concepts of CBWFQ. The next section discusses how WFQ and CBWFQ compare. Figure 18-2. How CBWFQ Works In the previous chapter, the WFQ algorithm was briefly introduced. Before diving in..
Using IP Helper Addresses for DHCP
The ip helper-address configuration command allows the router to forward local DHCP requests to one or more centralized DHCP servers: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z.Router1(config)#interface Ethernet0Router1(config-if)#ip helper-address 172.25.1.1Router1(config-if)#ip helper-address 172.25.10.7Router1(config-if)#exitRouter1(config)#endRouter1# The traditional role of routers in DHCP has been simply to act as a pro..
