I have a /29 range op IP addresses issued by my ISP. Is it possible using a Cisco 877 router to configure 1 or more of the 4 Ethernet ports in some way so that I could assign some of the public IP addresses to nodes, connect them to the relevant ports on the 877 and have the nodes publicly accessible over the Internet?
Best Regards & TIA,
It would be easy if you got a second address block from the ISP and you could put it directly onto a second VLAN. But it is not necessary.
The main point of doing the static NAT (providing a one to one translation of the private address on the node to a public address) would be that you could sit in an Internet cafe and access these nodes directly by the translated public address. This would not have any requirement for DDNS.
Note that the static NAT makes them accessible by IP address. A DNS entry (but not necessarily dynamic DNS) would be needed if you want to access them by name. Note that this same requirement applies if you get a second block of addresses from the ISP.
 the config that you posted shows dynamic NAT. And the problem with that is that while inside nodes can get publis addresses that it is variable what public address they would get and this prevents them from being accessible from the Internet. With the static NAT that I suggest you could map specific inside addresses to specific outside addresses. For example you could translate 192.168.0.5 to 159.xxx.xxx.58, and you could translate 192.168.0.22 to 159.xxx.xxx.59. This allows you to be in the Internet cafe and to directly access 192.168.0.22 by using 159.xxx.xxx.59.