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HOW MANY IP PHONES SHOULD I CONNECT PER VLAN???

Recommendations?

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Hall of Fame Super Red

Re: HOW MANY IP PHONES SHOULD I CONNECT PER VLAN???

Hi Alicia,

From this excellent CUCM Solution Reference Network Design (SRND) document;

A good rule of thumb is to limit the number of devices per VLAN to about 512, which is equivalent to two Class C subnets (that is, a 23-bit subnet masked Class C address). Typical access layer switches include the stackable Cisco Catalyst 2950, 3500XL, 3550, and 3750, as well as the Cisco 3560 and the larger, higher-density Catalyst 4000 and 6000 switches.

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Note: The recommendation to limit the number of devices in a single Unified Communications VLAN to approximately 512 is not solely due to the need to control the amount of VLAN broadcast traffic. For Linux-based Unified CM server platforms, the ARP cache has a hard limit of 1024 devices. Installing Unified CM in a VLAN with a IP subnet containing more than 1024 devices can cause the Unified CM server ARP cache to fill up quickly, which can seriously affect communications between the Unified CM server and other Unified Communications endpoints. Even though the ARP cache size on Windows-based Unified CM server platforms expands dynamically, Cisco strongly recommends a limit of 512 devices in any VLAN regardless of the operating system used by the Unified CM server platform.

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/6x/netstruc.html

Hope this helps!

Rob

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