Phone Registration in CUCM

[silvervoip]

Hello,

A quick question. I have been looking for the answer in SRND but unable so far. I will be glad if you have the answer.

I have 3 CUCM servers in the group and lets say 1st node in the group reached its capacity so I am expecting the 2nd node to be in play. 

How endpoints (phones, webex app etc) will handle this traffic? will endpoint still come to 1st node in the group and ask for registration then they will get registered to 2nd node?

or will they be aware that 1st node already reached its capacity so they wont bother 1st node and they will directly go to 2nd node in the group for registration?

[b.winter]

Hi,

there is no "hard" limit, on how many phones one node can handle.

Therefore, phones will always register to the node, that's first in the CM group.

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[silvervoip]

so, for end points to be able to registered to 2nd node in the cluster, should 1st one must be not reachable by ICMP?

[Jaime Valencia · Accepted solution]

Maximum Number of Registered Devices:	This parameter specifies the maximum number of devices that can register with Cisco CallManager and is used to limit the overall resource demand. Devices that count toward this limit include: Annunciator devices, H.323 gatekeepers, H.323 phones, H.323 gateways, ICT trunks (gatekeeper or non-gatekeeper-controlled), MGCP CAS trunks, MGCP gateways, MGCP FXS ports (analog ports), MGCP FXO ports, MGCP T1/E1 PRI, media termination points (hardware or software), transcoders, Music on Hold servers (not MOH audio sources), SIP trunks, IP phones, conference bridge devices (hardware or software), legacy Skinny Gateway Control Protocol devices like Cisco Analog Access, and video conference bridges (IP/VC 3540 configured with Skinny Client Control Protocol [SCCP] port). The following devices are NOT counted toward this limit: line appearances (directory numbers), route lists, Remote Destinations and built in bridges. It is to be noted that Jabber devices ( BOT / TCT) are counted as registered devices, even when they are not actually registered but just configured.
	This is a required field.
	Default: 5000
	Minimum:  5000
	Maximum:  20000

[b.winter]

No, the phone shouldn't be able to register to the first node via SIP / SCCP.

It sends out a e.g. a SIP REGISTER message to CUCM, which respondes with 200 OK.

But that's exactly what the CM group is for. To control, which phone should register to which node.

So, use this function. It doesn't make any sense, to block traffic between phones and nodes to control the signalling path.

Also for testing, there are different possibilities to achieve this (like changing the order in CM group).