I don't know how B&G handles it on their gear, but others like Furuno and Raymarine do not tend to support using external DHCP.  It's the chart plotter that assigns addresses, but most of their devices are also hard-coded to fall back on a specific IP addresses.  And they don't always just hand out IP addresses, there are sometimes other DHCP options that are also passed.  That and how some of them use multicast for broadcasting data is... a bit foreign to how a lot of 'normal' computer networks might get configured.  Oh, and they're not typically class C subnets either.  It's not a good idea to put other traffic onto the same network as the navigation gear.  Most vendors will tell you not to do this (and they're right).

I hear you on avoiding failure, but since it's the plotter(s) that handle the addressing, if they're offline it's not going to matter if the rest of the gear isn't getting an IP.

It's tempting to think "it'll all be great to be on the same network" but it's really not.  Not that it isn't within the realm of 'technically possible' but rather that a lot of the software on the plotters and other devices BARELY FREAKIN' FUNCTIONS ON IT'S OWN sometimes!  Having a ton of unrelated traffic on the 'same wire' will not help that.

I say this coming from 4 decades of experience with networks and have poked around at this idea myself now and then.  

Thanks for the thoughtful response.  As it turns out, it works fine to have the router be the DHCP server. Even B&G accepts this since they want their gear to get to the Internet for weather and updates. My question is whether I can put static addresses into the B&G gear.  It's just a compulsion to use static addresses for static configurations.  In case of router failure, I can re-enable DHCP on the Zeus and bring the system up independently, so this is not a critical issue.

BTW, I bought Furuno gear years ago because I liked the idea of an Ethernet interconnect.  Furuno didn't want external devices on the network but I tried and it was great. (As it happens, most of their stuff had a fixed, static class B address.) This meant that the computer at the nav station could display the radar, etc, and at the same time use a satellite link to download weather on transports.  And do email.  I suspect manufacturers don't like this because it complicates service more than that the ethernet can't handle the bandwidth. 

The Furuno setup was a dream since the same, independent, program runs on the boat, the computer, and the iPad/iPhone.  They really did a great job. And not just as remote screens, independently. This happened because they bought MacSea (Maxsea; T-Zero).  Iker Pryszo, who wrote the program knew computers.  Raymarine and B&G are more in their own private universe and seem to abjure integration.

As an example, in a stand-alone system, B&G won't broadcast AIS on their WiFi.  However, you can re-transmit it, and a boat router will then broadcast it. Why?

Shorter response...   From my experience, B&G does not have a fallback address.  If there is no DHCP server, they just don't communicate.  My experience with the older Furuno gear was that there was only fixed addresses.  

@lip I believe instead of putting the static address in the B&G, add it as a "reserved" address in the router. Yes, I know this only works if the router comes up before the B&G DHCP requests time out, but I assume you looked for the static configuration setup in the B&G and didn't find one. It seems that MFD programmers are not yet TCP/IP/Internet savvy.