Hello Chad
If I understand correctly, you want the following:
(ISP Network) --- (PE) --- (CE) --- (SW) --- (R1)
And you want the /29 subnet provided at the customer-facing interface of PE to be assigned to an interface on the CE as well as on an interface on R1, correct?
Well, the simplest way to achieve this would probably be to change the topology and have the SW connect directly to the PE, and then have the CE and R1 connect to the switch, on the same VLAN. I’m assuming however that you want to avoid such a scenario.
Well, one way to do it is to use a BVI in the CE so that the two ports on the CE will essentially act as two switchports, and the BVI will act as an SVI for those two ports. You can find out more about that at the following Cisco documentation:
Another option would be to use L2TPv3, but that would give you a layer 2 tunnel through the CE device without allowing it to actually obtain an IP address in the subnet you want.
This is a protocol that allows you to tunnel L2 over an L3 network regardless of whether you do it within your own network, or across two geographically remote sites, the concept is the same. But it really depends upon your topology and what you actually want to achieve.
In any case, such a scenario would be a little cumbersome to implement. Can you share with us what it is that you are trying to achieve so that we can see if there is another way of accomplishing it?
I hope this has been helpful!
Laz