IP ARP is widely understood and relatively simple. As a result, it is hard to ask difficult questions about ARP on an exam. However, the topics of Frame Relay Inverse ARP (InARP), its use, defaults, and when static mapping must be used lend themselves to being the source of tricky exam questions. So, this section covers Frame Relay InARP to show some of the nuances of when and how it is used. InARP discovers the DLCI to use to reach a particular adjacent IP address. However, ..
The show ip ospf virtual-links Command
The following command shows the configured virtual links: Router#show ip ospf virtual-links The show ip ospf neighbors command is also useful for discovering details about neighbors. Even though virtual-link partners might not be directly attached, they will show as neighbors because of the virtual connection. Example 7-11 shows the output of the show ip ospf virtual-links command. Example 7-11. The show ip ospf virtual-links Command Output Table 7-5 explains ..
Configuring IPX Type 20 Packet Forwarding
Many applications in the NetWare environment use the Network Basic Input/Output System (NetBIOS) request services from IPX servers. These services include session establishment and termination and information transfer. On a NetWare client, a NetBIOS application using IPX broadcasts type 20 propagation packets to all IPX networks to get information about named nodes on the network. NetBIOS uses named nodes for resources on the network. To communicate with these resources, Net..
The link-state request packet, OSPF packet type 3, is sent in response to a router during the database exchange process. This request is sent when a router detects that it is missing parts of the database or when the router has a copy of LSA older than the one it received during the database exchange process. Figure 9-5 shows fields in the link-state request packet. The request packet contains each LSA specified by its LS type, link-state ID, and advertising router. This uniq..
The trick behind this load balancing lies in the GLBP group. One router is elected the active virtual gateway (AVG). This router has the highest priority value, or the highest IP address in the group, if there is no highest priority. The AVG answers all ARP requests for the virtual router address. Which MAC address it returns depends on which load-balancing algorithm it is configured to use. In any event, the virtual MAC address supported by one of the routers in the group is..
