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New Member

No Dhcp option 150 and switch port not on voice vlan

Hello,

Two Quick questions first of we have call manager version 8. I will like to see if someone can explain a scenario we had at one of our site regarding not having  option 150 for our  dhcp server, but still the cisco 7941 phones were able to register to call manager but cisco phones did not have some ringers and phone services until we added dhcp option 150 all ringers and phone services worked. I thought u need option 150 for phones to make calls but in this case it didn't phones still register to call manager. Keep in mind this phones were previously register at another site and moved to this new site which didn't have dhcp option 150 for a bit. How is this possible for phones to work somewhat without option 150. Second question we had a phone which was connected to a switchport that only had data vlan but no voice vlan was configured but it still register to call manager and it worked any idea how it worked without having switchport on voice vlan only on data vlan?

Thanks,

3 REPLIES

Re: No Dhcp option 150 and switch port not on voice vlan

Voice and Data vlan are just an easy way to separate the two, they are not a necessity! remember softphones use the data vlan all the time.

About the option 150, It wont actually get chached, but once the phone has pulled up its config once (using TFTP), it will populate the Call Managers' IP addresses, through the Device Pool .Even though your DHCP pool has no option 150 IP address. (SETTINGS>device configuration>active call manager), in the new subnet, it will still keep pointing at the previsously obtained call manager IP's. this is why it will still function.

Things like ringtone, back grounds and missed call logs, fully depend on TFTP, so that explains why your you were not seeing this working without option 150



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New Member

Re: No Dhcp option 150 and switch port not on voice vlan

Hi Minkdennis,

So is there a difference a between tftp and call manager?

So how is the phones able to register to call manager are they using still dchp server to get IP address without option 150 or how are they keeping there previous IP address?

Thanks,

New Member

Re: No Dhcp option 150 and switch port not on voice vlan

Hi,

Option 150 is enabled for showing TFTP server path address and for downloading config files.

Bring some new ip phone,do not configure anything,but still you ip phone gets registered with some random Directory Number and locally those will be able to communicate.

Its some what like PC getting 169 series Ip address when there is no dhcp server.

Phone and switch might have exchanged cdp and started working.

In call manager we will configure,administrate and using TFTP Server phones will download all config files and its limits that we have configured.

Regards,

Guru

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