TelePresence VLAN

Answered Question
Feb 12th, 2010

We have one Communications Manager cluster to act as our PBX.  We recently purchased a new TelePresence system and a 2nd CM cluster which will be dedicated for the CTS.  The TelePresence SRND states to put the CTS codec in the Voice VLAN. There's no mention of what VLAN to put the 2nd dedicated CM cluster in.  I don't think that we can have 2 CM clusters on the same Voice VLAN so what would be the best practice for setting up the codec and CM cluster for the CTS?  Thank you.


http://www.cisco.com/en/US/docs/solutions/Enterprise/Video/tpendpts.html

Correct Answer by gogasca about 7 years 1 week ago

Hi,

Thats more a CUCM SRND question, but based on our CUCM SRND take a look at this:


http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/7x/netstruc.html#wp1043629


Typically, Cisco Unified Communications Manager  (Unified CM) cluster servers, including media resource servers, reside  in a data center or server farm environment. [...] Because these servers and  resources are critical to voice networks, Cisco recommends distributing  all Unified CM cluster servers, centralized voice gateways, and  centralized hardware resources between multiple physical switches and,  if possible, multiple physical locations within the campus. This  distribution of resources ensures that, given a hardware failure (such  as a switch or switch line card failure), at least some servers in the  cluster will still be available to provide telephony services. In  addition, some gateways and hardware resources will still be available  to provide access to the PSTN and to provide auxiliary services.    Besides being physically distributed, these servers, gateways, and  hardware resources should be distributed among separate VLANs or subnets  so that, if a broadcast storm or denial of service attack occurs on a  particular VLAN, not all voice connectivity and services will be  disrupted.

...


There is the potential for  large numbers of devices within a single VLAN or broadcast domain to  generate large amounts of broadcast traffic periodically, which can be  problematic. 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.


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.


To answer your question, yes, separate VLAN for CUCM servers, not only for clusters, (one cluster contains from 1 to 20 servers (super cluster))


Let us know if you have any other question

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Correct Answer
gogasca Sun, 02/14/2010 - 21:51

Hi,

Thats more a CUCM SRND question, but based on our CUCM SRND take a look at this:


http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/7x/netstruc.html#wp1043629


Typically, Cisco Unified Communications Manager  (Unified CM) cluster servers, including media resource servers, reside  in a data center or server farm environment. [...] Because these servers and  resources are critical to voice networks, Cisco recommends distributing  all Unified CM cluster servers, centralized voice gateways, and  centralized hardware resources between multiple physical switches and,  if possible, multiple physical locations within the campus. This  distribution of resources ensures that, given a hardware failure (such  as a switch or switch line card failure), at least some servers in the  cluster will still be available to provide telephony services. In  addition, some gateways and hardware resources will still be available  to provide access to the PSTN and to provide auxiliary services.    Besides being physically distributed, these servers, gateways, and  hardware resources should be distributed among separate VLANs or subnets  so that, if a broadcast storm or denial of service attack occurs on a  particular VLAN, not all voice connectivity and services will be  disrupted.

...


There is the potential for  large numbers of devices within a single VLAN or broadcast domain to  generate large amounts of broadcast traffic periodically, which can be  problematic. 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.


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.


To answer your question, yes, separate VLAN for CUCM servers, not only for clusters, (one cluster contains from 1 to 20 servers (super cluster))


Let us know if you have any other question

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