The EIGRP Topology Table

EIGRP uses three tables: the neighbor table, the topology table, and the IP routing table. The neighbor table keeps state information regarding neighbors, and is displayed using the show ip eigrp neighbors command. EIGRP Update messages fill the routers’ EIGRP topology tables. Based on the contents of the topology table, each router chooses its best routes and installs these routes in its respective IP routing table. An EIGRP router calculates the metric for each route bas..

EIGRP Reliable Transport Protocol

Five types of EIGRP packets exist, further categorized as reliable packets and unreliable packets. The reliable EIGRP packets are as follows: • Update— Update packets contain EIGRP routing updates sent to an EIGRP neighbor. • Query— Queries are sent to neighbors when a route is not available and the router needs to ask the status of the route for fast convergence. • Reply— Reply packets to the queries contain the status of the route being queried..

DSCP-Based Weighted Random Early Detection

DSCP-based WRED was introduced in Cisco IOS Software Release 12.1(5)T. DSCP-based WRED configures the WRED algorithm to use the AF drop-preference values (as defined in RFC 2597) of a packet's DSCP markings to influence its drop probability as queues fill. Remember that the second digit of an AF codepoint indicates drop preference and can range from 1 (lowest drop preference) to 3 (highest drop preference). For example, if DSCP-based WRED is enabled on an interface, AF23 woul..

Defining Per Port Privileges

To configure the privilege level of a particular line, use the following configuration command: Router1#configure terminal Enter configuration commands, one per line.  End with CNTL/Z.Router1(config)#line aux 0Router1(config-line)#privilege level 5Router1(config-line)#exitRouter1(config)#privilege exec level 5 show ip routeRouter1(config)#privilege exec level 1 show ip      Router1(config)#privilege exec level 1 show   Router1(config)#e..

Using HSRP Preempt

You can ensure that a particular router is always selected as the HSRP active router if it is available. On the router that you wish to make your primary active HSRP router, you need to set a higher priority level and use the standby preempt command: Router1#configure terminal Enter configuration commands, one per line.  End with CNTL/Z. Router1(config)#interface FastEthernet 0/1 Router1(config-if)#standby 1 ip 172.22.1.1   Router1(config-if)#standby 1 pr..