Identifying Issues That Might Need Escalation

Earlier in this tutorial we discussed the procedures that must be followed when issue escalation is required. Although any number of issues might need escalation, the Network objectives list specific scenarios in which escalation might be necessary. Each of these issues will not always require escalation; an administrator with an Internet connection and a little determination can track these down. Nevertheless, we quickly identify each of the issues listed in the CompTIA objectives:

• Switching loop-On an Ethernet network, only a single active path can exist between devices on a network. When multiple active paths are available, switching loops can occur. Switching loops are simply the result of having more than one path between two switches in a network. The Spanning Tree Protocol (STP) is designed to prevent these loops from occurring. If the packet in the loop is a broadcast message, the loop can create a full broadcast storm. Broadcast storms are discussed in this section. Switching loops occur at the data link (Layer 2) of the OSI model.
• Routing loop-As the name suggests, a routing loop occurs when data packets continue to be routed in an endless circle. In a proper operation, a router forwards packets according to the information presented in the routing table. If the routing table is correct, the packet takes the optimal path from the source to the destination. It is not common, but if the information in the routing table is incorrect through a manual misconfiguration or a faulty router route detection, routing loops can form. A routing loop is a path through the internetwork for a network ID that loops back onto itself. Routing loops are detectable because they can quickly bog down a network, and some packets are not received by the destination system.
• Route problems-Route problems typically occur when routing tables contain information that does not reflect the correct topology of the internetwork. Out-of-date or incorrect routing tables mean that packets cannot be correctly routed through the network, and route problems occur. Verify the routing table to ensure that it is correct. Sometimes static routes are entered and cause problems when the network topology is changed.
• Proxy ARP-The ARP protocol is used to resolve IP addresses to MAC addresses. This is important because on a network, devices find each other using the IP address, but communication between devices requires the MAC address. In a proxy ARP configuration, one system or network device answers ARP requests for another system. It is a proxy ARP because one network system is proxying for another's ARP communications.
• Broadcast storms-A broadcast address is an IP address that you can use to target all systems on a subnet or network instead of single hosts. In other words, a broadcast message goes to everyone on the network. A broadcast storm occurs when a network is overwhelmed with constant broadcast or multicast traffic. Broadcast storms can eventually lead to a complete loss of network connectivity because the network is bogged down with the broadcast storm. As with other network problems, you might suspect a broadcast storm when network response times are poor and people complain of a slow network. These broadcast storms can be caused by faulty hardware, such as a NIC that continually sends out data, switching loops, or even faulty applications running on the network. Baselines work well for identifying broadcast storms.