CISCO DPC3825

71a8juvlcol-_sl1500_The Cisco DPC3825 is a cable modem featuring an 802.11n access point. The product is actually made by Scientific Atlanta but private labeled for Cisco.

The Cisco DPC3825 wireless speed is adequate for the gigabit LAN speed. The use of an intranet works properly as well.

The upstream port is a standard F type connector for 75Ω coaxial cable. DOCSIS 3.0 speeds actually are faster than the wireless and LAN ports. Depend on location, some ISP plans may have 100 megabit or even 250 megabit service. Competition from fiber providers, cable companies have been forced to improved their performance considerably.

A complete set of advanced features makes this gateway much more useful for a corporate user. VPN tunnels work properly. Tunnels created with Windows also work properly.

We noticed some Cisco software being distributed by the driver CD for a $5 Realtek USB network adapter. This software is not required however it appears to be targeted to Cisco and Linksys wireless users. This USB adapter was purchased subsequent to the DPC3825.

Cisco has provided better quality home network equipment that allows users to expand their horizons. With the modern features we find the DPC 3825 to be a reasonable product. As example, we connected a machine running Windows Server and it worked without problems. Linux is widely used for network attached storage. Wi-Fi printers, DVD players and game consoles also connect fine.

By default the DPC3825 uses a narrow channel for wireless-n which provides 75 Mbps of performance. This is the same channel width used by 802.11g. There is an option to change to a wide channel which gives a faster 150 Mbps.

Another option for automatic channel should be enabled as well to get the best possible performance. 802.11n supports fully automatic channel selection to deal with the crowded Wi-Fi areas.

The  DPC3825 uses a 1T1R design which is a single antenna product. Its designed primarily for notebook users which tend to have limited wireless performance. Much better performance would have been realized with 2T2R radios which can provide much more bandwidth when copying larger amounts of data.

802.11n operates in the 2.4 GHz band which is very crowded. The standard uses sophisticated radio techniques to improve the connectivity compared to the older 802.11g even when using wide channels. The DPC does not support the use of 4.8GHz which is part of the 802.11n standard.

 

CABLE WAN SERVICE DOCSIS 1.0, 1.1, 2.0 and 3.0
LAN 4 port Gigabit Ethernet 1000BASE-T
WIRELESS PROTOCOLS 802.11b, 802.11g, 802.11n
WIRELESS SPEED 150 Mbps maximum 1T1R
USB included

The typical gaming machine is connected at 1 Gbps using at least cat7 cabling. Best is now cat 8 which can handle 40-100 Gbps easily. Unfortunately the DOCSIS 3.0 speeds will not be realized with the DPC due to the use of 1 Gbps Ethernet.

WI-FI

We have numerous different USB Wi-Fi Adapters. We use them instead of wired connections mainly for ease of installation. The Netgear A6200 is much faster then the Compaq Mini Fast Ethernet port. Recent 802.11ac adapters are a refinement of 802.11n with more room at 5 GHz when connected to a 802.11ac access point. Games with the A6200 experienced much less lag.

The A6200 also provides faster backups from a portable machine. Our Compaq Mini CQ10-450CA has a 802.11n which limits its performance somewhat. Using the A6200 the machine experienced a big improvement in speed when connected to the DPC3825.

SECURITY

The DPC3825 supports all of the improved wireless security protocols. WPA2 personal is the best option. The browser is secure even with a public unencrypted access point.

Generally its a good idea to change the Wi-Fi password every 3 months. This way its much less likely miscreants will be able to use the service. We developed a secure password tool intended to frustrate even large corporate data miners.

ISSUES

We have occasionally noticed the network fall back to 100 Mbps on the wired ports. Rebooting the Cisco DPC3825 and all of the connected machines is the only way to get the network speeds back. Using category 7 cables seems to be the best choice for gigabit speeds.

The Cisco DPC3825 also seems to run a bit warm suggesting the components are not extremely energy efficient. We did not notice any EPA Energy Star markings on the DPC3825. Our Asus PA238QR LCD Monitor is rated EPA Energy Star gold.

 

WIRELESS PERFORMANCE

Generally the Compaq CQ10-450CA with its Atheros adapter can get about 65Mbps while our Netgear USB A6200 can get 144Mbps. Actual throughput vary but even the A6200 runs slower than the fast Ethernet port.

ACCESS POINT

Many restaurants use the DPC3825 for their access point. Generally users are only using 10-25Mbps internet speeds. Recently 100 and 250Mbps service is now being offered which exceeds the DPC3825 wireless capability. To achieve higher speeds requires more antennas.

Given the DPC3825 is the interface to the cable co. its possible to add a 802.11ac access point. The DPC3825 is able to handle DHCP for many users, so it can have its wireless signal turned off and then used only for a gateway. Its even possible to use more than one additional access point to deal with larger areas.

One idea is to place one ore more access points in the attic. Power is easily available and Ethernet cable is easily placed. Infrequent access to upgrade makes the attic ideal.

Many business use wall mounted access points. Many install a plug for the PSU beside the desired location high on wall. The uplink is then routed through the plenum space.

The DPC3825 is seen in many coffee shops as an access point. The performance is generally good but it suffers when several are using torrents which tend to be very demanding.