Option 242 is used to give the phone the required parameters that it should use to connect to the PBX. There are two scenarios in which you can use option 242.
I am going to use the following VLAN IDs in my examples:
- VLAN 100 – PC/Server Network
- VLAN 200 – Voice over IP Netowrk
Scenario 1: Separate VLAN for Voice and Data
This is the most common configuration for VoIP networks. This works by having the option 242 set in both VLANs however it will be different in both.
First we need to set option 242 for VLAN 100
L2Q=1,L2QVLAN=200,VLANTEST=0
At this point our phone has gotten a DHCP lease that is telling it:
L2Q=1 meaning ON
L2QVLAN=200 meaning set the VLAN ID to 200
VLANTEST=0 meaning the timeout period for DHCP on that VLAN. 0=Infinite
Next we need to set option 242 for VLAN 200
MCIPADD=192.168.42.1,MCPORT=1719,HTTPSRVR=192.168.42.1,VLANTEST=0
Our phone has now switched it’s VLAN based on option 242 in VLAN 100. Now the phone, when requesting DHCP in VLAN 200 will get the option above. This will tell it:
MCIPADD=192.168.42.1 – this is the IP address of the PBX
MCPORT=1719 – Port the phone will listen on for signalling traffic to the call controller
HTTPSRVR=192.168.42.1 – Where to download firmware via HTTP. Typically same as PBX
VLANTEST=0 meaning the timeout period for DHCP on that VLAN. 0=Infinite
Now your phone should be booting in the correct VLAN and have the correct parameters pushed to it via DHCP.
Scenario 2: Shared VLAN for Voice and Data
The DHCP required for this scenario is much simpler. Simply add DHCP option 242 to your scope with the following string:
MCIPADD=192.168.42.1,MCPORT=1719,HTTPSRVR=192.168.42.1
MCIPADD=192.168.42.1 – this is the IP address of the PBX
MCPORT=1719 – Port the phone will listen on for signalling traffic to the call controller
HTTPSRVR=192.168.42.1 – Where to download firmware via HTTP. Typically same as PBX
Closing Notes
Please feel free to comment if you feel anything be added or better explained.
Very good article. Thanks. I have a question. Where to put this parameters ? In the 46xxsettings file or in the DHCP server configuration ? This is an unclear point for me.
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Hi bd, thanks for your comment. These options are placed in the DHCP server configuration.
What will happen is when you plug in a phone to your network it has no configuration. We need a way to tell it where it’s server is. The easiest way it through DHCP.
When the phone gets a DHCP address it will also get DHCP options along with that. For example (option 3 – Default Router) and (option 6 – DNS).
When it receives 242 the phone knows to look at that and use those settings in its own configuration.
I hope that helps.
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Hi Tony,
this was all fine until Avaya started the autoprovisioning Service in the cloud. Now the scenario with two vlans still works.
The scenario with only one Vlan for voice and data didn’t work out with a new IPO11.1FP1 for me, as the phones tried to fetch config from the cloud instead of the local IPO. Looks like the setting of mcipaddr, mcport and httpsrvr ist not sufficient any more. Maybe I start a packet capture at a time, to find out what the IPOs DHCP is presenting to the phones.
Regards, Rolf
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Hi Rolf,
I did some testing for you and I was able to get a phone to boot on 11.1FP1. I used the same steps in my guide.
I’d recommend you ensure that the DHCP options are correct (e.g. no spaces or hidden characters.)
Also what you can do is take a packet capture from the DHCP server to make sure that it is indeed sending out Option 242.
Avaya’s auto-provisioning service only kicks in as a last resort. Meaning that the phone did not get DHCP and does not have stored settings. I have a feeling though that the issue may be related to DHCP not sending.
Thanks for the comment and feel free to message me back if you still have issues.
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Hi Tony,
Have you had any luck getting option 242 to work when the DHCP server is on a CloudGenix ION router? The syntax a quite a bit different than a Cisco router.
Thanks,
Tim
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Hi Tim,
To be honest, I have not. I tried doing some quick googling for you and I haven’t found anything that shows how to configure them on that router.
Best of luck!
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Tony, THANK you, you’ve done a great job clarifying and making a great example / how to.
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Thanks for checking out my article. I’m glad it helped 🙂
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Hey, thanks.
I used this configuration for phones, separate vlan on my main site, and it works.
I want to do the same on a remote site. The DHCP server is located at the main site. Each of the 2 sites is connected via an MPLS operator network, I did all the routing. But the problem is the L2qVLAN part. VLANs are local to each site
VLAN 10 in site A is not equivalent of VLAN 10 in site B
I want to do the same on a remote site. The DHCP server is located at the main site. Each of the 2 sites is connected via an MPLS operator network, I did all the routing. But the problem is the L2qVLAN part. VLANs are local to each site
VLAN 10 in site A is not equivalent of VLAN 10 in site B
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Hi Aurelien,
Is your Site B using the same subnet and DHCP scope as your main site?
What is the VLAN on either side?
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