Thursday, May 31, 2012

FAQ to Help You Realize Cisco Aironet 1250 Series Access Point

The Cisco Aironet 1250 Series is a component of the Cisco Unified Wireless Network, which can scale up to 18,000 access points with full Layer 3 mobility across central or remote locations on the enterprise campus, in branch offices, and at remote sites. The Cisco Unified Wireless Network is the industry's most flexible, resilient, and scalable architecture, delivering secure access to mobility services and applications and offering the lowest total cost of ownership and investment protection by integrating seamlessly with the existing wired network.

There are several general questions to help you figure out what Cisco Aironet 1250 Series Access Point is.
Q: What is the Cisco Aironet 1250 Series Access Point?
A: The Cisco Aironet 1250 Series Access Point is the first enterprise-class access point to support the IEEE 802.11n draft 2.0 standard. With its modular design, the Cisco Aironet 1250 Series Access Point supports current and future wireless technologies, ensuring investment protection. With both 2.4-GHz and 5-GHz 802.11n draft 2.0 standard radio modules, the access point delivers total data rates of up to 600 Mbps, meeting the performance requirements of the most demanding applications. Integrated MIMO technology provides more reliable coverage and greater throughput for both existing 802.11a/b/g clients and new 802.11n clients in even the most challenging wireless environments. Users can now rely on wireless networks to give them a similar experience to wired networks, providing them with mobile access to high-bandwidth data, voice, and video applications regardless of their location.

Q: How does the Cisco Aironet 1250 Series Access Point fit in the Cisco WLAN product portfolio?
A: The Cisco Aironet 1250 Series Access Point Series is a critical component of the Cisco Unified Wireless Network solution and can be deployed in either standalone (autonomous) or unified (light weight) mode. The full breadth of Cisco unified wireless features and mobility services is only available when deployed in lightweight mode with a wireless LAN controller, and the Cisco Wireless Control System (WCS) management solution. The unified feature set represents the most comprehensive set of capabilities in the industry, including guest access, wireless intrusion detection and intrusion prevention, voice-ready services, scalable Layer 3 mobility, and location services. When configured with LWAPP, the Cisco Aironet 1250 Series can automatically detect the best-available Cisco Wireless LAN Controller and download appropriate policies and configuration information with no manual intervention. Access points deployed in standalone mode have a subset of capabilities suitable for basic enterprise deployments. Access points deployed in standalone mode may later be upgraded in the field to lightweight mode, thereby providing customers a smooth path to benefit from the complete set of unified features.

Q: What are the major benefits of the Cisco Aironet 1250 Series?
A: The Cisco Aironet 1250 Series has the following benefits:
RF Leadership: The Aironet 1250 Series is the industry’s first enterprise draft 11n AP. The Aironet 1250 Series supports physical layer (PHY) data rates up to 300 Mbps per radio, a greater than five-fold increase over the performance of 802.11a/g networks. Integrated MIMO technology improves coverage, reduces dead spots, and augments overall client throughput. Integrated RF management capabilities increase system capacity, improve system performance, perform automated self-healing to compensate for RF dead zones and access point failures, and provide a comprehensive way to manage spectrum.  Combined, these capabilities enhance reliability and throughput to provide a better overall end-user experience for users relying on the wireless network for business functions.
Investment protection: The Cisco Aironet 1250 Series is a powerful, modular and upgradeable platform that provides support for the IEEE 802.11n draft 2.0 standard today. Platform modularity ensures a smooth migration path to emerging higher-performance wireless technologies and future advanced services.
Extensive Interoperability: The Aironet 1250 Series Access Point has undergone extensive interoperability testing to ensure simple, secure interoperability with other 802.11 devices. It is the first Wi-Fi CERTIFIED 802.11n draft 2.0 access point, has earned the Intel Connect with Centrino certification, and has undergone extensive testing in 802.11n plug fests.
Enterprise-class security: The Cisco Secure Wireless solution provides a comprehensive approach to wireless security to help ensure the integrity of sensitive corporate information Cisco’s wireless security solution supports:
Standards-based authentication and encryption including support for 802.11i, Wi-Fi Protected Access (WPA), WPA2, and numerous Extensible Authentication Protocol (EAP) types. These certifications support IEEE 802.1X for user-based authentication, Temporal Key Integrity Protocol (TKIP) for WPA encryption, and Advanced Encryption Standard (AES) for WPA2 encryption.
Integration with the Cisco Secure Wireless solution, providing the industrys first integrated wired and wireless security solution.
Industry-leading wireless intrusion prevention system (IPS):
◦ Detects and suppresses rogue access points
◦ Mitigates sophisticated passive and active WLAN attacks
◦ Supports management frame protection (MFP) for day-zero intrusion detection
Management and deployment flexibility: The Cisco Aironet Series access points are key components of the Cisco Unified Wireless Network, a comprehensive solution that delivers an integrated, end-to-end wired and wireless network. Using the radio and network management features of the Cisco Unified Wireless Network for simplified deployment, the access points extend the security, scalability, reliability, ease of deployment, and manageability available in wired networks to the wireless LAN.

Q: What are the key similarities between the Cisco Aironet 1250 Series and the Cisco Aironet 1240AG Series?
A: Both series are designed for challenging RF environments such as factories, warehouses, and large retail establishments that require the antenna versatility associated with connectorized antennas, a rugged metal enclosure, and a broad operating temperature range.

Q: What are the key differences between the Cisco Aironet 1250 Series and the Cisco Aironet 1240AG Series?
A: The Cisco Aironet 1250 Series is the only Cisco access point designed to support the IEEE 802.11n draft 2.0 standard. It supports 10/100/1000 Ethernet and was specifically engineered to support the power, throughput, and mechanical requirements of MIMO and 802.11n. The Cisco Aironet 1250 Series is a modular, dual-band access point with a choice of 2.4-GHz and 5-GHz IEEE 802.11n draft 2.0 radio modules. The platform modularity ensures a smooth migration path to emerging higher-performance wireless technologies, including the final 802.11n standard. The Cisco Aironet 1240AG Series is a fixed-configuration access point and the 802.11a/b/g radios cannot be upgraded. The Cisco 1250 Series has 32 MB of flash memory and 64 MB of DRAM, while the Cisco Aironet 1240AG Series has 16 MB of flash memory and 32 MB of DRAM.

Q: Will the Cisco Aironet 1240AG Series become obsolete due to the introduction of the Cisco Aironet 1250 Series?
A: No. The Cisco 1240 Series provides a lower-cost rugged indoor 802.11a/b/g alternative for customers who do not require an access point that supports the IEEE 802.11n draft 2.0 standard.

Cisco Aironet 1250 Series Detailed Questions
Q: What are the powering options for the Cisco Aironet 1250 Series? Is the Cisco Aironet 1250 Series 802.3af-compliant?
A: The Cisco Aironet 1250 Series Access Point may be powered by a Cisco Ethernet switch, a power injector, or a local power supply.
The Aironet 1250 Series Access Point with one RM1252 radio module installed requires 12.95W, which is within the 802.3af Power over Ethernet standard.  Any Cisco switch supporting 802.3af may be used to power the Aironet 1250 Series Access Point with one RM1252 radio module installed.
Beginning late 2007, Cisco will enable auto-negotiating, single-port power for the Aironet 1250 Series access point on leading switches across the Catalyst portfolio. This unique, integrated solution provides the full power requirements for dual radio modules and eliminates the need to run an additional cabling drop or insert a separate power injector.
The Cisco Aironet 1250 Series Access Point may also be powered remotely using a Cisco Aironet Power Injector (AIR-PWRINJ4) or locally using a power supply (AIR-PWR-SPLY1).

Q: Can the Cisco Aironet 1250 Series be powered using both the DC input (that is, external AC power supply) and PoE? If both are used, do they load share? Or is it one or the other?
A: The Cisco Aironet 1250 Series Access Point can be powered by either PoE or the DC input. If the Cisco Aironet 1250 Series Access Point powers up over PoE (using either an 802.3af or a high-power injector), then that is the power source. If the Cisco Aironet 1250 Series is plugged into a DC power source, the access point resets and the unit is run from the DC jack and does not go through 802.3af discovery so the Ethernet port will not have power.

Q: Will third-party Power over Ethernet mid-span devices be able to consistently power the Cisco Aironet 1250 Series?
A: No interoperability testing has been done with third-party Power over Ethernet mid-span devices.

Q: What antenna options are available for the Cisco Aironet 1250 Series?
A: Several new antennas were specifically designed for the Cisco Aironet 1250 Series. To support the 2.4-GHz and 5-GHz IEEE 802.11n draft 2.0 radio modules with MIMO technology, new 2.4-GHz and 5-GHz ceiling omnidirectional antennas were developed. Each enclosure contains three antenna elements in a single white flush mount enclosure, providing an aesthetically pleasing option for installation in drop-ceiling office environments. Also available are new 2.4-GHz and 5-GHz straight dipole antennas in gray to match the accent colors of the Cisco Aironet 1250 Series access point. Table 1 contains a list of the new antennas being introduced with the Cisco Aironet 1250 Series.  Note that Cisco Aironet 1250 Series access points are certified for operation only with Cisco Aironet antennas; to ensure regulatory compliance, select Cisco Aironet antennas for use with Cisco 1250 Series Access Points.
For more information on antenna options, visit:

Table: 2.4-GHz and 5-GHz Non-articulating Dipole Antennas

Q: Will the articulating dipole antennas work with the Cisco Aironet 1250 Series?
A: Yes. These antennas are also supported for operation with the Access Point 1250 series.

Q: Is the Cisco Aironet 1250 Series UL 2043 plenum rated?
A: Yes. UL 2043 is a standard specified by Underwriters Laboratories. In the United States, most municipal building codes require certain UL certifications for equipment used in buildings. Municipalities often specify UL 2043 certification for equipment used in the plenum air spaces. Municipalities also define what they consider to be plenum air space. In some U.S. municipalities, the plenum air space includes only the area above a suspended ceiling.
In others, the area below the suspended ceiling may also be considered the plenum area.

Q: What client devices are compatible with the Cisco Aironet 1250 Series?
A: The Cisco Aironet 1250 Series is interoperable with any 802.11n draft 2.0, 802.11a, 802.11b, or 802.11g Wi-Fi-certified clients. Cisco has also conducted extensive testing to ensure interoperability with enterprise-class 802.11n draft 2.0 clients from leading manufacturers such as Intel and other major silicon vendors. Cisco has also completed Intel’s Connect with Centrino compatibility testing program to help ensure high performance and complete interoperability between our respective next-generation 802.11n draft 2.0 solutions.
In addition, Cisco clients and third-party Cisco Compatible Extensions (CCX) clients enjoy the enhanced wireless security and mobility capabilities provided by the Cisco Unified Wireless Network solution.

Q: Will the Cisco Aironet 1250 Series support the Cisco Unified Wireless IP Phone 7921?
A: Yes. The Cisco Unified Wireless IP Phone 7921 is Wi-Fi-compliant and will interoperate with any Wi-Fi-compliant access point, including the Cisco Aironet 1250 Series. The 802.11n standard ensures backwards compatibility for 802.11a/b/g devices.

Q: What is the coverage model of the Aironet 1250 Series with 802.11n draft 2.0 radio modules compared to existing IEEE 802.11a/b/g access points?
A: If you plan to replace your existing IEEE 802.11a/b/g access points with the AP1250, you can simply replace them one for one and experience enhanced wireless performance.

Q: Will my current WLAN controllers support the Cisco Aironet 1250 Series and 802.11n ?
A: All currently shipping WLAN controllers support the Cisco Aironet 1250 Series. These include:
Cisco Wireless LAN Controller Modules for Integrated Services Routers
Cisco 2100 Series Wireless LAN Controller
Cisco Catalyst 3750G Integrated Wireless LAN Controller
Cisco 4400 Series Wireless LAN Controller
Cisco Catalyst 6500 Series Wireless Services Module

Q: What considerations do I need to take into account when designing my controller infrastructure?
A: With a wide range of WLAN controllers to choose from, flexible controller deployment options, and ‘n+1’ controller scalability, Cisco’s Unified Wireless Network is designed to support both a gradual migration to 802.11n as well as an immediate large scale 802.11n deployment. This scale-as-you-grow flexibility is an ideal solution for customers looking for a flexible, customized solution for their pervasive wireless deployments.  As customers migrate from 802.11a/b/g deployment to 802.11n, no major redesign or re-architecture is needed for most customer deployments.

Q: Does the Cisco Aironet 1250 Series support bridging and backhaul functions, in addition to its access point function?
A: Yes. When operating in the standalone (autonomous) mode, the Cisco Aironet 1250 Series supports link role flexibility, providing both access point and bridge functions through configuration of each radio as an access point, repeater, root bridge, non-root bridge, or workgroup bridge (Table 2). This array of configuration flexibility enables the Cisco Aironet 1250 Series to address applications including basic wireless LAN coverage, wireless LAN coverage with wireless backhaul, and more traditional bridging applications.

Table 2: Cisco Aironet 1250 Series Deployment Options Overview

Q: Does the Aironet 1250 Series support dynamic frequency selection (DFS) to provide access to the channels in the UNII-2 and UNII-2 Extended bands?
A: Yes. The Cisco Aironet 1250 Series supports a very robust DFS algorithm, enabling the effective use of the UNII-2 and UNII-2 Extended bands in the United States, Europe, and other countries around the world. This is especially important for 802.11n deployments, where the additional channels can be leveraged to support a greater number of 40-MHz wide channels.

Q: Will the Cisco Aironet 1250 Series IEEE 802.11n draft 2.0 radio modules support 40-MHz channel widths in both the 2.4-GHz and 5-GHz bands?
A: Yes. Although 40-MHz channel widths are supported in the 2.4 GHz band, Cisco does not recommend using it because of the restricted amount of available spectrum; only one non-overlapping 40-MHz channel can be supported by the entire band. The 5-GHz band is much better suited to the use of 40-MHz channel widths.

Q: Which 802.11n packet aggregation modes will the Cisco Aironet 1250 Series IEEE 802.11n draft 2.0 radio modules support?
A: The Cisco Aironet 1250 Series IEEE 802.11n draft 2.0 radio modules support both A-MPDU and A-MSDU packet aggregation modes. These modes are supported for both transmit and receive functions.

Q: Will the Cisco Aironet 1250 Series IEEE 802.11n draft 2.0 radio modules support 802.11n legacy beam forming?
A: Yes. The Cisco Aironet 1250 Series IEEE 802.11n draft 2.0 radio module hardware supports legacy beam forming. Legacy beam forming uses an Open Loop mechanism to determine the coefficients necessary for forming a beam in the direction of the client. This feature will be enabled in a future software release.

Q: What accessories are available for the Cisco Aironet 1250 Series?
A: Additional accessories that can be ordered for the Cisco Aironet 1250 Series include:
2.4-GHz and 5-GHz antennas
Cisco Aironet Power Injector (AIR-PWRINJ4)
Cisco Aironet Power Supply (AIR-PWR-SPLY1)
Console Cable (AIR-CONCAB1200)
1250 Series Ceiling, Wall Mount Bracket kit; Spare (AIR-AP1250MNTGKIT=)

Q: What is the warranty for the Cisco Aironet 1250 Series Access Points?
A: Cisco Aironet 1250 Series access points come with the standard Cisco 90-day limited warranty for hardware and software, as described at

Q: What is the procedure for upgrading radios in the Cisco Aironet 1250 Series Access Points once future technologies become available?
A: The Cisco Aironet 1250 Series was designed as a modular and upgradable access point platform. When new radio modules become available, the old radio module may easily be removed and replaced in the field.
NOTE: Cisco Aironet 1250 Series Access Point Data Sheet

Q: What is IEEE 802.11n?
A: IEEE 802.11n is a new wireless standard designed to deliver an approximate five-fold increase over 802.11a/g network performance. 802.11n uses MIMO technology to increase the reliability and predictability of the wireless network by optimizing the effects of multipath propagation. The standard allows operation in both the 2.4-GHz and 5-GHz frequencies, and is backward-compatible with existing 802.11a/b/g networks. The Wi-Fi Alliance has begun certification of 802.11n products adhering to the draft 2.0 standard. This certification will ensure interoperability between access points and devices.

Q: What is the status of the Draft 802.11n version 2.0 standard?
A: The IEEE 802.11n working group has passed letter ballot, and this is what is known as 802.11 Draft 2.0. Subsequently, the Wi-Fi Alliance commenced compatibility testing in June 2007 to ensure interoperability of products adhering to the 802.11n draft 2.0 standard. The Cisco Aironet 1250 Series Access Point was selected as the reference platform for the Wi-Fi Alliance test bed. All products receiving Wi-Fi Alliance draft 2.0 certification must be tested with the Cisco Aironet 1250 Series Access Point. Further information can be found here Error!
Hyperlink reference not valid..

Q: What is the status of the final 802.11n standard?
A: The final standard is expected to be ratified in Sep 2008 but this date may change as the working group continues its work.  The current IEEE timeline for 802.11n ratification may be found at

Q: When will the final 802.11n solution from Cisco be available?
A: Cisco works closely with and monitors all relevant IEEE standards, including 802.11n. Shortly after 802.11n ratification occurs, Cisco plans to deliver solutions that are compliant with the final 802.11n standard.

Q: Will Cisco guarantee that the Cisco Aironet 1250 Series can be upgraded to support the final 802.11n standard?
A: Cisco cannot guarantee that the current Cisco Aironet 1250 IEEE 802.11n draft 2.0 standard radio modules can be software-upgraded to support the final 802.11n standard. However, the modularity of the Cisco Aironet 1250 helps ensure that should the final 802.11n standard require a hardware modification, the impact will be limited to just the radio modules, and will not require a change to the access point. The Cisco Aironet 1250 Series radio modules are field-upgradeable and easy to change.

Q: What is multiple-input multiple-output (MIMO) technology?
A: Multiple-input multiple-output (MIMO) technology uses advanced signal processing with multiple antennas to improve the throughput, reliability and predictability of the wireless LAN.
By operating with multiple transmitters and receivers, MIMO-based access points can take advantage of the effects of multipath propagation to decrease packet retries and improve the fidelity of the wireless network. The benefits of MIMO technology extend to 802.11a/b/g clients in the form of improved reliability and predictability of the network. More consistent throughput and improved reliability will provide a better overall end-user experience for high-bandwidth data, voice, and video applications.

Q: How is it possible to increase the typical throughput for 802.11a/b/g and 802.11n clients with MIMO, when the data rates for the clients are fixed by the 802.11 standard?
A: Access points and clients equipped with MIMO smart antenna technology are able to receive signals more reliably over greater distances than those with standard diversity antennas. This means that 802.11 data rates extend further from the access point using MIMO than with a standard diversity access point. For example, a client operating at a specific distance from an access point with standard diversity may be experiencing data rates of 36 Mbps, as compared to sustaining 54 Mbps when connecting to an access point with MIMO.

Q: What about my investment in 802.11a/b/g?
A: 802.11a and 802.11g each offer a 54-Mbps data rate, supporting a broad range of applications, including voice and video. With the relative under-utilization of these frequencies, especially the 5-GHz band, and the large installed base of 802.11a/b/g clients, most enterprises should anticipate their investments in business-class 802.11a/b/g access points to have many years of service. Additionally, the 802.11n standard requires backward compatibility with existing 802.11a/b/g infrastructure. Cisco expects 802.11a/b/g and 802.11n technologies to coexist for a long time.

Q: Do Distributed Antenna Systems (DAS) work with 802.11n?
A: MIMO technology relies extensively on multiple transmitters and multiple receivers to attain the throughput, reliability, and predictability benefits of 802.11n. The current generation of DAS systems only support a single transmit/receive chain per access point. Therefore, the throughput, reliability, and predictability benefits of 802.11n will be lost when used in conjunction with a DAS.

Q: What are the differences in performance between a 2x3 and a 3x3 MIMO implementation?
A: Theoretical calculations show that a 3x3 radio will have slightly better performance over a 2x3 radio. However, in our real world performance testing we have not seen any significant performance differences between 2x3 and 3x3 implementations.  Note that the current generation of both 2x3 and 3x3 802.11n silicon supports up to 2 spatial streams, so there is no throughput advantage for a 3x3 implementation.

Friday, May 25, 2012

Wireless Bridge Vs. Access Point

Wireless bridge and access point offer radio link connectivity over a computer network, but they are structurally and functionally designed to serve slightly different purposes. Setting up a vast wireless network for a corporate office space requires the installation of many networking devices that facilitate connectivity over the entire network. Two such devices are 'Wireless Bridges' and 'Wireless Access Points'. Since both have overlapping areas of functionality, there seems to be confusion regarding how they differ from each other.

Does anyone know the differences between bridges and access points? Are they the same thing? And any info of wireless bridges vs. wireless access points.

Can anybody tell me what the difference between a wireless Bridge and an Access Point?

I am confused in Concepts of Access Point and Wireless Bridges.
What i have figured out is that Wireless bridges relay frames between 802.11 WLAN and 802.3 LAN.
What about AP?

I have a Linksys 10/100 wireless router with several computers connected to it, both wired and wirelessly.

I recently purchased a ReplayTV digital video recorder for my living room, which I attach to my router via an ethernet cable every two weeks to download new program listings from the Internet. I would like to replace this cable with a wireless solution by buying a wiress device and plugging my ReplayTV into it, and having this device give me access to the Internet through my router.

My question is: A) Do I need a wireless access point or a wireless bridge, and B) what's the difference between the two?

All the questions mentioned above show that many network users may be confused with what are wireless bridge and access points, and the main difference between Wireless Bridge and Access Point.

Well, let’s have an overview on wireless bridge and access point, the main features, the main difference…

Wireless Bridges
A computer network tends to be divided into various segments that need to be integrated together. A network bridge connects such divided network segments together, facilitating data sharing. Before the advent of Wi-Fi technology, network bridges were connected through wired ethernet cables. Specifically, in context of the OSI model, network bridges connect segments on layer 2 (data link layer).

These are intelligent devices compared to hubs and repeaters, that control data flow to and fro, from the connected network segments. A wireless bridge performs the same function of linking network segments, but it does that through a Wi-Fi link, instead of a wired ethernet link. It can connect two networks together with a radio link, to facilitate connectivity and data transfer between them.

Such bridges may also be used to connect an ethernet network, with an access point or wireless router, for Internet connectivity. Using a 'Wireless Distribution System', bridges are set up to connect multiple networks. There are more than one types of wireless bridges, ranging from basic ones, which facilitate ethernet connectivity with a wireless access point, to ones that double up as a wireless access point and a bridge. That seems to be the source of confusion between the two devices.

Wireless Access Points
Wireless access points primarily provide Internet access by connecting wireless devices with routers. They act as extenders of a Wi-Fi network, by directly providing Internet access over long distances. Popularly known as 'Wireless Hotspots', they are some of the most widely used networking instruments. Thus a wireless access point provides Internet and LAN connectivity to multiple devices simultaneously.

Some wireless access points also provide the functionality of a wireless bridge, by providing connectivity between two wireless networks. Modern access points can connect more than 200 wireless devices simultaneously. Some wireless access points are in fact wireless routers which directly provide Internet access, through connection with a modem.

Wireless Bridge vs. Access Point
Firstly, look at the simple illustration of wireless bridge and Access Point:
Wireless Bridge 
<Wired LAN>---<Wireless Bridge> ------ <Wireless Bridge>---<Wired LAN>

<Wired LAN>---<AP>----<Wireless Clients>

In the *strict* use of the terminology, the following does NOT work

<Wired LAN>---<AP> ------ <AP>----<Wired LAN>

The AP cannot associate with an AP. 

With that being said, this is usually a software limitation and a lot of AP's can actually function as a bridge.

The central point of difference between the two devices lies in their functionality. While wireless bridges are designed to integrate two physically separated networks through a radio link, an access point connects multiple wireless devices with a router. Thus, a wireless bridge connects two computer clusters together and a wireless bridge connects multiple devices with a single Internet connection simultaneously. A bridge can also be used to connect an existing ethernet network with an access point.

Though wireless bridges and access points were separately manufactured before, today a combination of these two devices is more popularly used. These devices offer both bridging and multiple device wireless connectivity. Therefore, the boundary between the functionality of both devices has become blurred. If you are thinking of buying a wireless access point/bridge device, make sure that you go for a 802.11n wireless networking standard based device, which offers the highest data transmission speed currently.

More Related Wireless Info:
List of Featured Cisco Access Points for Enterprises
Cisco’s New Aironet Wireless Access Points Make Networks Faster and Steadier

In common wireless usage, a "bridge" is a device which allows for a wireless connection between two physically-isolated wired networks. A wireless LAN bridge can interface an Ethernet network directly to a particular access point. This may be necessary if you have a few devices, possibly in a far reaching part of the facility, that are interconnected via Ethernet. A wireless LAN bridge plugs into this Ethernet network and uses the 802.11 protocol to communicate with an access point that's within range. In this manner, a bridge enables you to wirelessly connect a cluster of users (actually a network) to an access point. Most wireless game adapters are transparent bridges as well.

Access points connect multiple wireless clients to each other and to a wired network. A non-bridging access point will allow association of wireless users, but will generally not allow you to connect to a remote wired network, or to another wireless access point (since they lack a common transparent bridging protocol to replicate the MAC to port table on both ends). Note that there are some access points that can operate in wireless bridge mode as well.

Some access points can also do WDS (wireless distribution system) which can connect to other access points at the same time as client radios. WDS is effectively a store and forward repeater between access points.

wireless bridge is a hardware component used to connect two or more network segments (LANs or parts of a LAN) which are physically and logically (by protocol) separated. It does not necessarily always need to be a hardware device, as some operating systems (such as Windows, Linux, Mac OS X and FreeBSD) provide software to bridge different protocols. This is seen commonly in protocols over wireless to cable. So in a sense the computer acts as a bridge by using bridging OS software.

Many wireless routers and wireless access points offer either a "bridge" mode or a "repeater" mode, both of which perform a similar common function, the difference being the bridge mode connects two different protocol types and the repeater mode relays the same protocol type. Wireless routers, access points, and bridges are available that are compliant with the IEEE802.11a, b, g and n standards. The frequency bands for these wireless standards can be used license-free in most countries.

Wireless bridge devices work in pairs (point-to-point), one on each side of the "bridge". However, there can be many simultaneous "bridges" using one central device (point to multipoint).

Bridging can be via WDS (Wireless Distribution System) which creates a transparent Level 2 wireless bridge between two or more points. Alternately the bridge can be set up as an access point – client relationship which requires the wireless devices used for the bridge to be set to the same service set identifier (SSID) and radio channel.

An example of a point-to-point bridge application would be connecting two commercial buildings. An example of a combination point-to-point bridge and point to multipoint application would be connecting multiple farm buildings.

Bridging has historically referred to propagation of data across a device without traversing a network stack, such as TCP/IP. Wireless bridging is a colloquial term. A more accurate description of connecting two local area networks would be a Wireless LAN to LAN Bridge. The distinction is important. While a device may not support bridging to a remote wireless access point to connect two LANs, it may be desirable (and supported) that a wireless access point support true bridging; where packets traverse from a wireless to wired network without passing through an internal protocol stack, firewall or other network abstraction. Two bridged networks could be treated as parts of a single subnet under Internet Protocol (IP). A wireless client would be able to make a DHCP request to a wired DHCP server if the wired and wireless networks were bridged. In the ISO OSI model, a device in which packets traverse the network layer is considered a router; a device in which packets traverse the data link layer only is considered a bridge.

Sunday, May 20, 2012

Cisco Nexus 5500, A Viable Core Switch for the Midsized Enterprise?

Mix of Nexus 5500 & Catalyst 6500?
Hi there,
Does Nexus 5500 series require a Nexus 7000 parent device? or it will be supported with Catalyst 6509? 
If this is the scenario : 
CAT6509 - Core Layer 3
CAT6509 - Distribution Layer 2/3
NX-5548 - Access Layer 2
 And FYI, no VSS on Catalyst 6509.
 Thanks in advance,
---A Q from Cisco Support Community.

For years, the Cisco Catalyst 6509 has been the workhorse of small and medium-sized enterprises, used for access, aggregation and core layers. Yet modern CPUs, motherboard chip architectures, virtualization, and more powerful storage arrays are moving the data center performance bottleneck back to the network infrastructure, creating demand for performance that exceeds the 6509. While some might think the Cisco Nexus 7000 would be the obvious replacement, midsized companies could benefit more with a Cisco Nexus 5500, specifically the Nexus 5596UP, as their network core switch.

Why not just upgrade the Catalyst with a Supervisor 2T to replace the core switch?
With new traffic demands on the Catalyst 6509, one upgrade option is certainly a new Supervisor and line cards to keep the old 6509 fighting. However, those upgrades aren’t trivial expenditures. Plus, it’s well known that Cisco has exhausted the raw forwarding capability of the 6500 with the Supervisor 2T.

Why not go with the Nexus 7009 as a core switch replacement?
The Cisco Nexus 7009 could be viewed as the natural 6509 successor, as, its form factor is similar to the 6509, allowing for a forklift upgrade without having to allocate additional rack units in the data center. Furthermore, the Nexus 7009 will even mount into a 2-post rack while its bigger brothers, the 7010 and 7018, require a 4-post rack. The Nexus 7K family of line cards also offers high port densities of 10GbE at favorable levels of oversubscription, as well as a migration path to 40GbE and 100GbE.

These are all great benefits, but the Nexus 7009 is a pricey bit of gear. Additionally, if an IT shop specifies a pair of the gear to build in the resiliency, then it becomes pricey times two. The list price for a Cisco Nexus 7009 bundle containing 2 Supervisor-1 engines, 5 Fabric-2 modules, and 2 6KW power supplies, the enterprise L3 feature license, and a single Fabric-2 48-port 10GbE line card, totals up to a whopping $157,500.  That total doesn’t even include the 10GbE optics that must be purchased. If you add a year of 24x7x4 SNTP SmartNet coverage, that’s another $13,600 to add to the OPEX budget.

Enter the Nexus 5K: A network core switch alternative
If the Supervisor 2T and Cisco Nexus 7009 aren’t the right fit, the question then becomes: what is a viable replacement for the Catalyst 6509 that will meet growth demand for 10 GbE ports without busting the budget? The market is replete with choices of densely packed 10 GbE L3 switches from Juniper, Arista, Brocade, HP, and others. However, for a Cisco-centric shop, the Nexus 5596UP could be the answer.

The Nexus 5596UP may have a small 2U footprint in the data center, but packs a lot of packet forwarding punch, offers multi-chassis link aggregation and fault-tolerance when configured according to Cisco best practices.

Additionally, the Nexus 5596UP is a non-blocking 10GbE switch that ships with 48 fixed ports and three slots that can be populated with additional modules. In order to use the 5596UP as a core switch, engineers will have to use one of those slots with the L3 routing engine expansion card (Version 2 boosts maximum host count to 16K), while leaving two blank slots that could be filled with 16 more 10GbE ports each. Adding the L3 enterprise software license makes a 48-port, 10 GbE switch with a full complement of routing features that can be expanded to 80 10GbE ports. That’s quite a lot of network forwarding capacity crammed into a 2U form factor. In fact, the Nexus 5596 has upsides at both L2 and L3:
  • Non-blocking at L2: Every port on a 5596UP is capable of forwarding at line-rate, full-duplex without dropping a frame. At Layer 2, it’s theoretically impossible to overwhelm the 5596UP; a frame received is a frame delivered when a switch is non-blocking.
  • Up to 160Gbps at L3 (240Mpps): While not a jaw-dropping statistic, 160Gbps of inter-VLAN traffic is a rather large number for a small enterprise, and not the sort of throughput that most small data centers are likely to approach. While aggregated vMotion, backup and storage traffic could potentially surge beyond the 160Gbps mark, most network designs isolate these sorts of traffic flows to a single VLAN. For example, vMotion traffic doesn’t get routed, therefore doesn’t take a chunk out of the 160Gbps number.

Will the Cisco Nexus 5596UP break the bank?
From a throughput perspective, the 5596UP sounds reasonable for a small data center application. Yet, does the Nexus 5596UP meet core switch replacement and cost parameters? The chassis, version 2 of the L3 routing engine and the enterprise L3 license, list at a total of $51,800, plus $2,800 to the annual OPEX budget for 24x7x4 SmartNet coverage. Be sure not to overlook that OPEX number for annual SmartNet renewal, as the number is over four times higher for the 7009 versus the 5596UP. Like the Nexus 7009 numbers listed above, this total does not include optics, but note that the 7009 and 5596UP use the same optics. For comparison purposes, the optics cost is a wash.
---Original reading from

More Notes:
Cisco Nexus 5500 Platform Switches
The Cisco Nexus 5500 Platform supports the following application scenarios, many of which require the installation of other products:
•As an access-layer switch, it can be used purely as a 1- and 10-Gigabit Ethernet switch, consolidating 10 Gigabit Ethernet connections into a smaller number of server connections trunked to the aggregation layer.
•As a smaller-scale aggregation switch, it can be used as a Layer 3 1- and 10-Gigabit Ethernet switch, consolidating multiple 1- and 10-Gigabit Ethernet connections from a data center access layer.
•In conjunction with the Cisco Nexus 2248T GE Ethernet Fabric Extender, the Cisco Nexus 5500 Platform can be a high-density 1-Gigabit Ethernet switching system, consolidating more than 900 Gigabit Ethernet connections within a single management plane.
•In conjunction with the Cisco Nexus 2232T 10GE Fabric Extender, it can be a high-density switching system, consolidating more than 600 10-Gigabit Ethernet connections within a single management plane.
•In conjunction with the Cisco Nexus 2224TM 10GE Fabric Extender, it can be a high-density switching system, consolidating more than 600 10-Gigabit Ethernet connections within a single management plane
•As a rack-level I/O consolidation platform, the switch carries Ethernet traffic from servers to the aggregation layer and carries FC traffic to existing Fibre Channel SANs.
•As a crucial element in data center I/O consolidation, the switch enables I/O consolidation at the access layer and provides interoperability with the Cisco Nexus 5500 Platform and other standards-based products.

CiscoNexus 5000 Series Switches (Cisco Nexus 5548, Cisco Nexus 5596 Switches) Data Sheet
CiscoCatalyst 6500 Switches: Cisco Catalyst 6000/6500, Aim at Enterprise Network & Service Provider Networks