Netgate SG-1000 microFirewall

Author Topic: VoiP LAN device stuck on DHCP renewal  (Read 238 times)

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Offline JKnott

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Re: VoiP LAN device stuck on DHCP renewal
« Reply #15 on: February 14, 2018, 01:37:24 pm »
Quote
There some MDNS and other garbage from Linux PC I don't know yet how to completely stop when wiresharking from Linux side.

This is where creative use of capture filters comes in.  You could create an filter that allows DHCP and also filters on the client and server MAC addresses.  For example, it might be something like port 67 or port 68 and (ether host <MAC1> or ether host <MAC2>), with <MAC1> and <MAC2> being replaced with the actual MAC addresses of the client and server.  This should result in only the desired captures.

I can't speak about the VoIP provider, but pfSense is an excellent firewall that does much more than much of the competition.

Offline gryest

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Re: VoiP LAN device stuck on DHCP renewal
« Reply #16 on: February 14, 2018, 01:46:34 pm »
Understood, the key word is "creative". I need bit more practice in filters.
Here is complete file in case.

Offline JKnott

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Re: VoiP LAN device stuck on DHCP renewal
« Reply #17 on: February 14, 2018, 01:59:52 pm »
Option 50, in the request, shows the address 192.168.1.107 is being requested.  The ack shows the correct client address, but for some reason is being sent to the broadcast address.  I have no idea why it would do that.  On my own system, the ack is sent to the correct client address.  The problem with sending to the broadcast address is the client has no idea the ack is for it.  When the broadcast IP address is used, the broadcast MAC address is also used.  A proper ack is sent to the assigned IP address, using the client's MAC address.

So, the question now becomes, why is the ack going to the broadcast address?

Offline gryest

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Re: VoiP LAN device stuck on DHCP renewal
« Reply #18 on: February 14, 2018, 02:21:50 pm »
I have no idea. I become suspicious about broadcast address from the beginning after I've got mentioned failures and started capturing traffic.

Offline gryest

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Re: VoiP LAN device stuck on DHCP renewal
« Reply #19 on: February 18, 2018, 11:35:28 am »
I got another look on DHCP sequence and compared to other devices. In short, VoiP controller receiving what was requested in DHCP Discover poll. VoiP set Broadcast flag 0x8000 and pf sense replied to broadcast address accordingly. Other PC and devices do not set Broadcast flag and pfSense replying to machine IP address as mentioned by JKnott.
  The other thing, Wireshark shows End option missing in DHCP Discover which is normally (255) End.
But most important, for some reason VoiP do not reply on received DHCP Offer basically not following protocol. Correct protocol handling happening during soft/hard restart only which make me pretty much sure it's VoiP device software problem.
Thanks for tips.