第6个模块：实现园区网的高有效性-2-优化HSRP CCNP交换部分中文版 教学课件.pptVIP

* Purpose: This slide discusses how one router may exist in multiple HSRP groups. Emphasize: To facilitate load sharing, a single router may be a member of multiple HSRP standby groups on a single segment. Each standby group emulates a single virtual router. There can be up to 255 standby groups on any LAN. Increasing the number of groups in which a router participates increases the load on the router and can impact the performance of the router. Discuss the example. Transition: Following discusses ISL links and HSRP. * Purpose: This slide discusses how multiple groups transmit data over a single link. Emphasize: Routers can simultaneously provide redundant backup and perform load sharing across different IP subnets. For each standby group, an IP address and a single well-known MAC address with a unique group identifier is allocated to the group. The IP address of a group is in the range of addresses belonging to the subnet in use on the LAN. However, the IP address of the group must differ from the addresses allocated as interface addresses on all routers and hosts on the LAN, including virtual IP addresses assigned to other HSRP groups. Work through the example. Transition: Following continues the discussion of multi-group HSRP. * Purpose: This slide discusses the standby debug command. Emphasize: HSRP supports the debug command. To enable HSRP debugging, enter the debug standby Enabling the debug facility displays the HSRP state changes and debugging information regarding transmission and receipt of HSRP packets. Caution the students that because debugging output is assigned high priority in the CPU process, this command can consume router processing cycles. Other commands that are supported by HSRP. Standby authentication assigns an eight character password to the group. This command is useful in preventing configuration errors. The default authentication string is cisco. Standby mac-refresh alters the interval at which packets are sent to refresh the MAC cach