Avoiding Routing Loops When Redistributing
Routing loops occur when a routing protocol redistributes routes into another protocol and then receives the same routes back—a process called route feedback. Because the metric is reset through redistribution, the routing protocol could see the redistributed path as more attractive. The potential for confusion is enormous, as shown in Figure 11-3; routes distributed from OSPF to EIGRP are distributed back to EIGRP at two redistribution points, causing the routing tables of..
RSVP is a soft-state signaling system that enables receivers to reserve resources for incoming traffic flows. Flows are identified by destination address and the transport-layer protocol, and are, therefore, unidirectional. The destination address can be a multicast group address; therefore, from an RSVP perspective, unicast flows are simply a special case of multicast. More specifically, in the unicast case, it is not necessary for a host to join a group prior to reserving r..
Easy VPN is a Cisco feature that allows you to deploy IPsec remote access devices easily using Cisco VPN Client software; their 800, 900, and 1700 series routers; the VPN 3002 hardware client; and the 501 and 506E PIX security appliances. Policies are defined on the Easy VPN Server and pushed down to the Easy VPN Remotes during IKE Mode Config. However, as you'll see in this section, the configuration of the Easy VPN Server function from the router's CLI is not a simple ende..
Managing the Router's ARP Cache
Every LAN device has an Address Resolution Protocol (ARP) cache. This is a table that the device uses to map Layer 2 MAC addresses to Layer 3 IP addresses. Without this mapping, the device could build its IP packets, but couldn't build the Layer 2 frames to carry these packets. Devices discover the information in the ARP cache dynamically. If a device needs to send a packet to an IP destination, and it doesn't have a corresponding MAC address, it sends out a broadcast ARP re..
Monitoring PPP over Frame Relay
The PPP over Frame Relay feature is configured between two Cisco routers, as shown in Figure 10-4. This figure is used to explain the show and debug commands for PPP over Frame Relay. Figure 10-4. PPP over Frame Relay Configuration Between Two Routers Example 10-3 shows the configuration files of routers R1 and R2. Example 10-3. Running Configuration of R1 and R2 ! R1 <output omitted> interface Virtual-Template1 ip address 192.168.1.2 255.255.255.0 ..
