Order / Timing of Booting Modem and pfsense PC

mer

On Comcast, with a Zoom cable modem (my device, not a Comcast one)
What I've noticed:
If pfSense is up and modem not fully on network, pfSense WAN seems to get a private IP (link local IPV4 if I remember correctly), but when modem comes fully on network, WAN gets an IP from Comcast.
So if both powered on at same time, pfSense WAN may get an unroutable address for a little bit, then as modem comes online WAN gets a new address.

I think you could test your hardware by simply leaving pfSense off, wait until modem gets fully on network, then power on pfSense. At that point it should get an IP from your ISP.
Then test the case where pfSense is up and modem reboots (like maintainence) and see what happens.

stephenw10

Yup if the modem bounces the link when it syncs with the cable then pfSense will pull a new lease. Not all modems do.

provels

Maybe it's not needed any more, but I've had this set for a long time in Interfaces / WAN / DHCP Client Configuration:

mer

@provels Nice. That would cover what I see temporarily in my configuration. Of course it assumes the modem is always at 192.168.100.1.

But nice.

provels

@mer I imagine it could depend on the brand of modem, but it's be a fixed IP in the Netgears and Motorolas I've had. Or if the modem even offers DHCP in the first place.

johnpoz

@mer said in Order / Timing of Booting Modem and pfsense PC:

Of course it assumes the modem is always at 192.168.100.1.

That IP is pretty common across the makers of modems, sure it could be something else.. But if you get a lease in the 192.168.100.x, its not like the modem would change its IP from 192.168.100.1 to 192.168.100.Z etc..

I have a arris S33 and that is the management IP, all the previous modems I have had over the years it has always been that 192.168.100.1 IP..

mer

@johnpoz @provels I know that "unstated industry standard" is 192.168.100.1, but I've learned the hard way that assuming may cause problems.
Now if IANA had something stating 192.168.100.1 is the default address for devices like cable modems, I'd accept that as gospel

:)

johnpoz

@mer nobody said its gospel and they all use it.. But clearly you got an IP in the 192.168.,100.x range - what I stated is if your device is in fact using 192.168.100.1 - its not going to change to say 192.168.200.1 out of the blue..

montreel

I see several responses mentioning having the modem leasing IPs. At the risk of exposing an embarrassing gap in knowledge:

If the modem is in bridge mode, I thought that it did not in and of itself "have" any sort of IP address?
I thought it was just a MAC-based "conduit" appliance for the ISP to actually connect to a client/gateway?
If the modem is in bridge mode, does it have any sort of DHCP functioning?
If I have the modem fully rebooted and "online" in bridge mode after a service outage: Why does my pfsense box not boot & bind to the modem? I have to boot a live Linux USB first to get the modem to bind with my igb0 WAN.

I will use the "Reject leases" suggestion. I will try the WAN MAC interfaces "spoof" & input the MAC of the WAN igb0. Hope it helps.

stephenw10

Some modems will run as a dhcp server if the upstream cable fails to sync so that a client can access it for diagnostics. That can happen even if its in bridge mode normally.

It might not in your case but you should be aware it can.

montreel

@stephenw10 thanks