Summary of Rules for Routes Advertised in BGP Updates
The following list summarizes the rules dictating which routes a BGP router sends in its Update messages: ■ Send only the best route listed in the BGP table. ■ To iBGP neighbors, do not advertise paths learned from other iBGP neighbors. ■ To eBGP neighbors, do not advertise paths for which the neighbor’s AS is already in the AS_PATH PA. ■ Do not advertise suppressed or dampened routes. ■ Do not advertise routes filtered via configuration. The first two rules..
Finding an Alternative Path to a Remote Network
When the path to a network is lost, EIGRP goes to a lot of trouble to find an alternative path. The method that EIGRP uses to find alternative paths is very reliable and very fast. The following list describes the process after a neighbor goes offline: 1. The router marks the routes that were reached by sending the traffic to that neighbor. 2. The router looks in the topology table, which has every advertisement received, to determine whether there is an alterna..
Hierarchical Queuing Architecture for Frame Relay
When Frame Relay encapsulation is configured for serial interfaces on Cisco routers, two levels of queuing can exist for the serial interfaces. By default, when the Frame Relay interface is congested, the interface-level queue is used to store the excess packets at the interface level until the interface becomes free to send them. In addition, a second level of queuing at the Frame Relay PVC level is possible with Frame Relay Traffic Shaping. NOTE WFQ is the default queuing..
By default, a switch operates in Per-VLAN Spanning Tree Plus (PVST+) mode using traditional 802.1D STP. Therefore, RSTP cannot be used until a different spanning-tree mode (MST or RPVST+) is enabled. Remember that RSTP is just the underlying mechanism that a spanning-tree mode can use to detect topology changes and converge a network into a loop-free topology. The only configuration changes related to RSTP affect the port or link type. The link type is used to determine how ..
Using HSRP for Home Agent Redundancy
For this recipe, we must configure two nearly identical Home Agent routers. Here is the configuration of the first one: RouterHome1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. RouterHome1(config)#interface FastEthernet0/0 RouterHome1(config-if)#ip address 192.168.9.2 255.255.255.0 RouterHome1(config-if)#standby 1 ip 192.168.9.1 RouterHome1(config-if)#standby 1 name HA-GROUP RouterHome1(config-if)#exit RouterHome1(config)#route..
