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SF300-24p, 2 vlans, 1 mitel pbx, a firewall, me, and my orchestra!

Level 1
Level 1

Hello Everyone,

Let me start by saying that I am NOT a network Engineer. I only play one 8 hours a day at my job that I kind of got by default. I have done alot of networking on a small scale in the past, but never with vlans, ip phones, etc..

That being said, please be gentle, and talk to me like I am a idiot.

I have read nearly every post on this forum that when I searched for "sf300" pulled up. But, I can not find anyone post that helps me in my situation. I may be suffering from information overload.

We have a mitel 3300 PBX that is our DHCP server. It feeds an old Foundry Networks switch that nobody knows the password for anymore so I can't even look in it to get some clues. What I think I know is this.

vlan1 = PC's subnet 10.0.0.X

vlan2 = phones subnet 10.1.0.X

Phones plug into the switch, PC's plug into the phone.

I am assuming this to be the case becase all the PC's get those numbers and when booting up a phone it comes up and says "vlan2 pri 5" during the DHCP discovery.

Like I said the Mitel 3300 is the DHCP server and our internet access is from the firewall's trusted port.

I won't bore you with everything I have tried. It would take way to long. So I will tell you what happens and maybe someone can tell me what I am missing.

I have put the switch in L3 mode via the console.

No matter what I try, the PC will always get IP addresses in vlan2's subnet. Even if I plug the PC directly into the switch.

Anyone have any ideas??? I have factory reset this baby and all I have done at this point is put it back in L3 and changed the default ip address so I can get to the web GUI.

Is there a guide out there that I can't find? or maybe a bullet point step by step on what needs to be setup to make this work right?

Any and all help is greatly appreciated....



9 Replies 9

Level 1
Level 1

Hi Bill,

If you set a port on the SF300 to an “Access” port for VLAN 1 and plug the PC into it and get an IP address from the mitel on VLAN 2… You may have a configuration issue on the DHCP portion of the mitel PBX.  It’s just a guess but if I were to see that on a network I would imagine that basically the 10.0.0.x network and the 10.1.0.x are living in the same untagged VLAN.  This could reproduce the symptoms of what you are experiencing.   However I am curious, when you say that you are plugging into the switch is that out SF300 or the Foundry?

Thank you,

Jason Nickle

Hello Jason,

Thanks for your reply!

I would agree with you. But If I plug the PC directly into the Foundry (old switch) it get the right number (10.0.0.X) Its only if I plug the Mitel into the Cisco that it gets the vlan2 numbers. I have not actually tired that with the port in Access mode so I will add that to the list of things to try. Frankly, I am not even sure "how" to configure the port to plug the mitel in! I assume it needs to be a Trunk. But I don't know that for sure.

If you have anything to add please do. I just appreciate being able to talk with someone that as some idea what I am dealing with. I am a "one man dog and pony show" So I got nobody to even bounce ideas off of.

Thanks again for your reply!


Your right, the port going to the mitel should be a trunk port and both VLAN 1 and VLAN 2 should be associated with it.  Typically on the SF300 it should be 1 as the untagged VLAN and 2 as the tagged.  You may need to confirm these settings on the mitel but data traffic(PC) is hardly ever tagged from the router.


Jason Nickle

I did a Factory reset and did the following.

Set the IP4 interface to

I opted to NOT set l3 because at this point I would just like to get the DHCP working, I will deal with the inter-routing between all our subnets later.

Hooked the mitel to the GE1 port set to trunk

Made vlan2

set port 1 to access

untagged vlan1

tagged vlan2

entered the DHCP address and turned on DHCP relay

Switched the laptop I am using to do the configurations with to "obtain address automatically"


Still I get a Vlan2 Address it should be a 10.0.0.X number from Vlan1.

I am totally confused. I don't understand why this does not work. I have looked through the Mitel configuration and found nothing obvious. It clearly says vlan1 is subnet 10.0.0.__ and vlan2 is subnet 10.1.0.__.

I really wish I could get into the old switch. I bet that would give me some clues. But like I said, the password and userame is long forgotten. I have tired the the default to no avail and from what I can tell the only way to get back in it is to Factory Reset it, if I do that I loose the configuration that I need to get in to see in the first place.

So...any guesses??? Anyone??? Gonna call our Mitel Vendor on Monday AM and see if they can shed some light.

Thanks again!


Out of curiosity, what happens if you set your DHCP server port as trunk 1u, 2t?

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-Tom Please mark answered for helpful posts

I did have the port set to 1u"p", 2t

I am not even sure what pvid I don't know if that would make a difference or not.

a friend of mine had an idea, he asked me if I was sure that I only had  1 dhcp server? He said maybe the mitel does one subnet and that old  foundry is doing the other...But I looked up the specs and I cannot see that the foundry is capable of acting as a dhcp server. Thinking about firing up wire shark and seeing if I can SEE what is happening for sure.

If you think it will help I will try the setting WITHOUT the pvid tonight  and see. If you don't think it will make any difference than I won't..Its a big headache to test this thing, I have to take down our entire phone system so it can only be done at night.

Let me know what you think...and thank you very much for your reply.


When the DHCP server receives a layer 2 DHCPREQUEST broadcast, it will fill this request for the scope that corresponds to the subnet of the interface that the DHCPRQUEST was received on. When it receives a request as a layer 3 unicast from a DHCP relay agent, it will fill the request out of a scope with a subnet that includes the GIADDR address.

A packet capture needs to show you are receiving the layer 2 broadcast.

Additionally, since you're using just the switch and only the switch, that DHCP server needs to know how to put traffic on the wire for whatever vlan it is not a member of. This will be accomplished either through 2 physical connects or tagging traffic by the server. Otherwise, need the layer 3 device.

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-Tom Please mark answered for helpful posts


Well its clear that I am in way over my head here. Cause I did not understand that at all!

The good news is that I did have a discussion with out Mitel people and I think..I have a better understanding of what needs to happen. But my Mitel guy did say something that I have not been able to figure out. Aparently, our current switch (Foundry Networks) has a "DHCP Helper file" in it that is telling the DHCP server what to do with request of IP's within the scope of the 10.0.0.X numbers.

I have googled and search but have found nothing on this for my particualar switch. Which leads me to believe that its called something else or done in some other fashion on this SF300-24P.

Any thoughts on this???

By the way...I can not thank you all enough for the help your giving me...I do really apreciate it.



Bill, can you email me a phone number? I'd like to give you a ring this evening.

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-Tom Please mark answered for helpful posts