About CCNA ICND2 certification:  ICND2 (640-816), short for  Interconnecting Cisco Networking Devices Part 2 is required to be passed when a candidate is pursuing two-exam CCNA certification path. The other exam that needs to be passed is CCENT. This exam tests a candidate's knowledge and skills required to successfully install, operate, and troubleshoot a small to medium size enterprise branch network. The exam covers topics on VLSM and IPv6 addressing; extending switched networks with VLANs; configuring, verifying and troubleshooting VLANs; the VTP, RSTP, OSPF and EIGRP protocols; determining IP routes; managing IP traffic with access lists; NAT and DHCP; establishing point-to- point connections; and establishing Frame Relay connections.

1. ISL: A Cisco proprietary trunking protocol, associated with Ethernet.. Supported by Catalyst switches and routers. ISL uses "encapsulation" of Ethernet frame for multiplexing multiple VLANs over a trunk line.
2. 802.1Q: This is an IEEE standard for the VLAN trunking protocols, associated with Ethernet. A VLAN identifier is inserted into the frame header, a technique called frame tagging.
3. 802.10: A Cisco proprietary method for transporting VLAN information inside the standard 802.10 FDDI frames.
4. LANE : LANE stands for LAN Emulation and is associated with ATM. This is an IEEE standard for transporting frames over ATM networks.

To verify any configuration change, "show vtp" privileged executive command can be used. This command displays, among other things, VTP domain name, VTP password if any, VTP pruning mode (enabled or disabled) and the IP address of the device that last modified the configuration.

1. NAT allows several hosts be connected to Internet by using fewer globally unique IP addresses. This in turn results in conserving the scarce public IP addresses. The terms public / global is used in the sense that the IP addresses are globally unique and officially registered.
2. NAT supports load sharing on inside machines. The inside machines are accessed in a round robin fashion, thus sharing load.
3. NAT offers some degree of security since IP addresses are not easily traceable. This is because, the actual host IP that is accessing the Internet is translated into outside IP address and vice versa. Thus, NAT offers protection against hacking.
4. One disadvantage of NAT is that it increases delay. This is obvious since address translation is involved.
5. Another disadvantage of NAT is that, when an application uses physical IP address, it may not function properly. This is because the physical IP address is changed by NAT.

1. The command:
show frame-relay pvc 100
displays the traffic statistics for PVC 100. The out put include input packets, output packets, BECN packets, FECN packets, etc.
2. The command
show interface serial 0
displays whether the interface is up, line protocol is up, LMI type, LMI DLCI, among other details.
3. The command
frame-relay lmi
displays the LMI traffic statistics.
4. The command that displays the current map entries is:
show frame-relay map.

The command 'show ip ospf interfaces' shows the summary information for OSPF interfaces. The information provided include autonomous system number, router id, designated router id, backup designated router id, hello time, and adjacent neighbors.

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