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duetgroup_tech
New Contributor

Fortigates incompatibility with Telenet DOCSIS 3.1 E-ROUTER

Hello all.

 

 

If you are using a Fortigate with the Belgian Cable ISP Telenet, you should know that there is a known incompatibility between Fortigates and the new Telenet DOCSIS 3.1 E-ROUTER. This is the kind of router that they install for all new clients. For now, it is possible to request Telenet to install a DOCSIS 3.0 modem and that solves the issue, but going forward this could become a big problem, especially if they require all their clients to switch to DOCSIS3.1.

 

The problem seems to be that Fortigates don't support Unicast DHCP. 

 

As far as I can tell the incompatibility is known to Telenet, but I don't know if Fortinet knows or not. I have opened a TAC case to find out.

 

13 REPLIES 13
mjcrevier
New Contributor III

I saw similar issues with Netgear modems used by Comcast in the States. Wonder if they use the same hardware.

emnoc
Esteemed Contributor III

Can you explain unicast DHCP? The whole purpose of DHCP is the client has no "address" so how is unicast used here? Outside of a DHCP-relay concept, DHCP is broadcasted 

 

Ken Felix

PCNSE 

NSE 

StrongSwan  

duetgroup_tech

From what I understand, "Unicast DHCP" is a misnomer.

Unicast refers to the Broadcast flag set in the Bootp flags. The Fortigate sets it to "Broadcast", whereas regular Windows/MacOS clients set it to "Unicast".

emnoc
Esteemed Contributor III

Interesting i would have to capture a DHCP datagram,  but broadcast and unicast just determines  the action of the DHCP-offer as 0.0.0.0 or x.x.x.x in  the offer from my understanding.

 

In the above you would need to look at the offer and witness is being set imho. I would use a dhcp-tool to test the above with the ISP and see what's happening or grab the difference 2 or more different devices for comparison.

 

Ken Felix

 

PCNSE 

NSE 

StrongSwan  

waterboy1602

Hi,

 

I'm experiencing exactly the same problem. Did you already found a fix for this or did you just change your modem with a DOCSIS 3.0 one?

 

I just swapped my DOCSIS 3.0 for a 3.1 one, but didn't do enough research to find this before hand. Can I possible fix this with the 3.1 modem?

avka1453

Hi,

 

Does anyone know if this issue has been resolved with a fortinet update?

 

thanks

waterboy1602

I can tell you that in the mean time this bug has been fixed. I'm using a DOCSIS 3.1 E-ROUTER from Telenet with a Fortigate firewall myself and the bridging functionality works without flaws.

avka1453

That's great! Which version are you on?

 

Kind regards,

waterboy1602

Any idea how I can find on which version I am?