Example of OSPF Network Types and NBMA

On NBMA networks with an OSPF network type that requires that a DR be elected, you must take care to make sure the correct DR is elected. The reason is that the DR and BDR must each have a PVC connecting it to all the DROther routers

Summary of PIM-DM Messages

This section concludes the coverage of PIM-DM. Table 20-2 lists the key PIM-DM messages covered in this chapter, along with a brief definition of their use. Table 20-2 Summary of PIM-DM Messages   The next two short sections introduce two other dense-mode protocols, DVMRP and MOSPF

Mitigating Detrimental Effects of the LDP Restart

As discussed previously, when the LDP control-plane component of an LSR restarts, it causes the failure of LDP sessions between that LSR and its peers. As soon as a peer detects the failure of an LDP session with the restarting neighbor, that peer immediately terminates the concerned LDP session and...

Variable-Length Subnet Masks

A variable-length subnet mask (VLSM) is designed to allow greater use of IP address space by borrowing bits from the subnet mask and allocating them to host devices. To allow a greater number of devices to connect to the Internet and intranets, the standards bodies of various routing protocols desig...


With the emergence of voice traffic into data networks, the need to differentiate between the various classes of service has become greater. PQ/CBWFQ, most commonly known as LLQ, is a new feature that provides a strict priority queue for voice traffic and a weighted fair queue for each of the other ...

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