cisco ccna labs

cisco ccna labs.. PVCs are similar to leased lines and are always available. while SVCs are similar to telephone circuit-switched connections that are established when data needs to be sent and removed after the data has been transmitted. PVCs are most appropriate when the information being transmitted is latency sensitive or when data is to be transmitted continuously; SVCs are suitable for occasional transmission of information or as a backup connection.. LMI specifies how the Frame Relay DTE and DCE interact and is only locally meaningful. There are three LMI implementations: ITU-TAnnex AANSIAnnexD and GangofFouro Cisco routers automatically detect the LMI type. By default, the Cisco router sends an LMI query message every 10 seconds and a full status update message after every five query messages.. DLCIs are used to locally identify the VC,they are the address of the VC. This numbering is only meaningful locally, so the DLCI can vary from hop to hop.. The FECN bit is set when the frame encounters congestion on its way to the destination DTE. In this case, the destination DTE will send a frame with the BECN bit set to the source DTE, indicating that congestion has occurred.. The command encapsulation frame-relay specifies the encapsulation type. There are two frame types: cisco and ietf, where cisco is the default setting and ietf is an open standard used in multi-vendor environments.. To explicitly specify the LMI type. use the command frame-relay hni-type. the Cisco router can automatically detect the LMI type. To troubleshoot LMI. use the following commands: show interfaces show frame-relay Imi and debug frame-relay lmio. To configure a manually resolved PVC, use the command frame-relay map. local broadcasts and multicasts will not be propagated through the VC if the parameter broadcast is not specified. Reverse ARP is used for dynamic resolution. this is done when a full status update is received and the VC is found not to be manually resolved.. There are three VC statuses: active (VC is operating normally between two DTEs), inactive (VC is operating normally between at least the DTE and the DCE), and deleted (the connection between the local DTE and the local DCE is not operating normally). o To view the PVC, use the command showframe.relay pvc; to view the resolution entry, use the command show (frame~relaymap). In a partially meshed network, routers have VC connections only to some (not all) of the routers. The star (central branch) topology is partially meshed. Partial-mesh networks that use VCs have a horizontal segmentation problem. to solve this problem. use the following Chapter 25 Frame Relay 715Any of the following solutions can be used: use a full mesh topology, use static routes, disable horizontal segmentation, or use subinterfaces. When using subinterfaces, the encapsulation and LMI type are configured on the physical interface, while all other configuration is done on the subinterface. To remove a subinterface from RAM after deleting it, you need to save the configuration and reboot the router. When solving horizontal segmentation problems, you must use point-to-point subinterfaces. To associate a VC to a subinterface, use the command frame-relay interface-dlcio