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—otherwise, LSA flooding will not be possible. So, with partial meshes, the election should be influenced by configuring the routers’ priority and RIDs such that the hub site of a hub-and-spoke partial mesh becomes the DR. Figure 10-3 shows an..

Configuring OSPF with the Broadcast Network Type

With the broadcast OSPF network type, neighbors are automatically discovered and the hello timer is faster than with NBMA. Configuring a broadcast interface just involves changing the OSPF network type—no neighbor statements are required.  The broadcast OSPF network type works best with a fully meshed network. Example 6-3 shows a typical configuration of the broadcast OPSF network type.  Example 6-3. Configuring a Broadcast Network

Circuit-Switching Links: Synchronous Optical Network

Synchronous Optical Network (SONET) was defined in the 1980s as a standard by which carriers could build multivendor transport infrastructure. SONET is divided into three areas: Physical, Payload, and DCC.   SONET uses a frame structure that repeats itself every 125 ms, enables providers to set up a hub topology rather than just point-to-point connections, and supports a fiber optic ring, which is created by fiber optics. In case of a failure, a bidirectional ring..

Certificate Enrollment Protocol

CEP is a protocol jointly developed by Cisco and VeriSign, Inc. CEP is an early implementation of Certificate Request Syntax (CRS), a proposed standard to the IETF. CEP specifies how a device communicates with the CA, how to retrieve the CA's public key, and how to enroll a device with the CA. CEP uses Public Key Cryptography Standards (PKCS). CEP uses HTTP as a transport mechanism and uses the same TCP port (80) used by HTTP. Note You can find more details on CEP at http:..

Data Structures of IP Routing Protocols

As traffic is routed through a network, the routers encountered along the way from the source to the destination need consistency in how they route traffic. For example, if one router selected the best path based on hop count, and another router selected the best path based on a link’s bandwidth, a routing loop could conceivably occur. Fortunately, having a common routing protocol configured on all routers within a topology helps ensure consistency in routing decisions. T..