Determining the gateway IP from a /29 question

Hi everyone,

I'm trying to configure a router for a customer and just trying to get some info in advance. The customer has a cable modem in bridge mode with a /29 connected to their current firewall. They told me the /29 range but not the gateway when I asked by email. Before I go back and ask for it I wanted to check if maybe it's always a certain one, like the first IP or something in a /29 or something obvious. This is not their range but just a made up one, but if it was something like 208.163.16.244/29, if there's a a particular one used by the modem/gateway, and what the one for the router would be. Thanks!