Switch-I0S-1-IDS# Configuration of the IDSM is quite different from that of other devices, and is a topic for a book unto itself. FlexWAN modules. FlexWAN modules allow the connection of WAN links such as T1s as well as high-speed links such as DS3s up to OC3s. There are two types of FlexWA modules: FlexWAN and Enhanced FlexWAN. The primary differences between the two versions are CPU speed, memory capacity, and connection to the crossbar fabric bus. Enhanced FlexWAN modules use the same WAN port adapters used in the Cisco 7600- series routers. The module is Layer-3 specific and requires either a Supervisor-720 or a Supervisor-2 with an MSFC to operate. When running in hybrid IOS mode, the Flex- WAN interfaces are not visible to Layer 2 with CatOS. Communication Media Modules. The Communication Media Module (CMM) provides tel- ephony integration into 6500-series switches. This fabric-enabled module contains three slots, which accept a variety of port adapters. The port adapters available for the CMM include Foreign eXchange Service (FXS) modules for connection to analog phones, modems, and fax machines; T1/E1 CAS and PRI gateway modules; conferencing and transcoding port adapters that allow confer- encing services; and Unified Survivable Remote Site Telephony (SRST) modules that will manage phones and connections should the connection to a Unified Call Manager become unavailable. The port adapters can be mixed and matched in each CMM installed. A 6500-series chassis can be filled with CMMs and a supervisor, providing large port density for VoIP connectivity. CatOS Versus IOS Cisco Catalyst switches originally did not run IOS-the early chassis-based switches were CatOS-based. This was because the technology for these switches came from other companies that Cisco acquired, such as Crescendo, Kalpana, and Grand Junction. CatOS may appear clunky to those who have used only IOS, but there are some distinct advantages to using CatOS in a switching environment. One of these advantages can also be considered a disadvanta