Private VLANs on the Catalyst 6000

The Catalyst 6000 product line has introduced some enhancements to the switching arena for security purposes. We will discuss some of these in this section and see how they can be a useful security element in Layer 2 design. A normal VLAN does not allow devices connected to it to be segregated from each other on Layer 2. This means that if a device on a VLAN becomes compromised, other devices on the same VLAN can also be attacked from that compromised device. Private VLANs ..

Single-Homing Scenario: Addresses Taken from Outside the Provider's Address Space

The routing rules discussed so far, along with the nature of a network's address space and whether it is single-homed or multihomed, have implications for whether and how the network can aggregate addresses. This section and the next three sections examine several scenarios. In the single-homing scenario, the customer is connected to a single provider and has IP address space totally different from the provider's. This could have occurred because the customer changed provider..

Configuring OSPF in a Nonbroadcast Environment

This section illustrates the configuration commands needed for implementing OSPF in a nonbroadcast environment. Interfaces default to the NBMA OSPF network type in a nonbroadcast environment. To change this, apply the ip ospf network command on the interface, as follows:  Router(config-if)#ip ospf network {broadcast | non-broadcast | {point-to-multipoint [non-broadcast]}}  For example, to change the OSPF network type to point-to-multipoint the command would be ip ..

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..

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..