I'm configuring a router that has a /27 of Internet IP's assigned, the router itself is assigned the IP x.y.z.130/27 and the remainder of the subnet (.131-.158) is NATd through to various IPs on the LAN side (10.x.x.x).

Have set up something similar in the past with a smaller subnet so it was easy enough to add the LAN IPs to the configuration as x.y.z.131/32, x.y.z.132/32, etc Obviously that becomes a little more awkward with a /27 or other larger subnet. Is there any "shortcut" to setting up the router to process the entire subnet without specifying each of the IP's separately? I had thought in the past at one point in another configuration that I'd been able to instead specify the subnet ie. x.y.z.128/27 but that does not seem to be working here (whereas specifying all 30 addresses individually as /32s does).

Mike

Couple options here:

You could use netmap similar to this: viewtopic.php?t=107311
You're just using the Public addresses routed to your service in place of local IPs.

Alternatively you could set your router up as the gateway of a DHCP server in the Public IP subnet (of which it already has an address) - then hand out Public IP leases to your devices directly instead of NATing. Bear in mind you will need to create an address list and exclude these from any src-nat or masquerade rules you may have in place at the gateway router.

Just brainstorming, let me know what you think.

The first thing about using multiple IPs on single interface is answer to the question: how does link peer (i.e. ISP router) deliver packets using those IP addresses?

Good point, I took the liberty of assuming the subnet was routed to OP by the peer (ISP).

Yup, its easy to fall into the assumption trap!!

Best thing is for every op.
a. to describe their WANIP ISP setup
b. provide a network diagram
c. provid config /export hide-sensitive file=anynameyouwish

Then there is less guessing and quicker resolution of issues.]
Personally I prefer to understand the user requirements and not talk about config or solutions until the needs are known.

Sorry got pulled away on another project, thanks for everyone's responses. In particular @mkx I've known this but your explanation of why is the clearest I've seen.

With that said, what I was really asking for clarification in this case is when I do have to add the IPs to the router, do I have to add each IP individually, or is there a shortcut to add the whole subnet?

So am I adding 254 individual lines like this...
/ip address add address=1.2.3.1 interface=Bridge1 network=1.2.3.1
/ip address add address=1.2.3.2 interface=Bridge1 network=1.2.3.2
/ip address add address=1.2.3.3 interface=Bridge1 network=1.2.3.3
...
/ip address add address=1.2.3.254 interface=Bridge1 network=1.2.3.254

Or can I do something like this to accomplish the same?
/ip address add address=1.2.3.1/24 interface=Bridge1 network=1.2.3.0

Obviously with smaller subnets it's not a big deal either way, but on bigger subnets like /25, /24, etc that ends up as a lot of lines if they have to be done individually. Unfortunately in this case I'm doing changes on a router that a) I didn't orignally configure and b) that is live ... so I don't have the option to "test and learn" as I might otherwise do.

Cheers,
Mike