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mmercerctu
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Joined: Mon Dec 08, 2014 7:47 am

CRS125 behind non bridging Modem with DHCP

Tue Dec 16, 2014 8:45 am

Greetings All,

Slowly working my way through configuring my network the way I want, but I am stuck on one thing...

I have ATT Uverse (we have FTTP/FTTH/Fiber whichever you're used to hearing it as ;) ) -- The modem/gateway is the NVG589, and unfortunately, unlike with the 510, you *cannot* turn off the DHCP server on this device.

Right now, I have it configured to do passthrough, I have the dhcp pool as small as I can set it to be (running a /30, it wont let me do a /31 or I would have). Now unfortunately, that means that it does at least have the ability to issue *1* dynamic address...

I already have the mikrotik acquiring my public ip address, but if I connect a device to the mikrotik, it has the ability to get the dhcp address from the NVG (dual dhcp on a single network without isolation is BAD).

Curious if anyone knows a way I can block this dhcp pool; I literally have 0 use for it, other than to manually set an address and connect to it.

Currently, I have the NVG setup as:

192.168.255.254/30
pool: 192.168.255.253

.253 is set as a "static lease", but if that device is not connected, or similar, the NVG makes its own rules on what to do (downright stupid).

The CRS is setup as:
192.168.26.0/27
192.168.26.1

Lease: 192.168.26.2-192.168.26.30

Looking for any suggestions on how to block this, as the device does not have an actual bridge mode, only passthrough.

Thanks!
 
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gabrielpike
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Joined: Thu Apr 17, 2014 4:17 pm

Re: CRS125 behind non bridging Modem with DHCP

Tue Dec 16, 2014 5:06 pm

Why not block port 67 and 68 into the gateway interface of the mikrotik?

add action=drop chain=input dst-port=67 in-interface=ether1-WAN protocol=udp src-address=192.168.255.254
add action=drop chain=input dst-port=68 in-interface=ether1-WAN protocol=udp src-address=192.168.255.254
Gabriel Pike
MTCNA

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