The challenge with SSH access on exe.dev arises from the need to share IPv4 addresses among multiple virtual machines (VMs). Each VM typically has its own unique IP for straightforward SSH connections, but exe.dev operates on a flat-rate subscription model that limits the number of available IPv4 addresses. As a result, standard HTTP requests, which use the Host header to route traffic to the correct VM, can’t be applied to SSH connections, since SSH lacks a similar mechanism. To address this issue, exe.dev implemented a system where each VM is assigned a unique public IPv4 address from a pool, rather than sharing a single IP among all VMs. The DNS resolution for each VM points to this unique address, which is mapped to a CNAME record. When an SSH connection is initiated, the client sends its public key and connects through a specific IP address. The combination of the user's public key and the IP address uniquely identifies the VM being accessed. Creating this proxy requires careful management of IP allocations based on user ownership and involves complex cross-system communication. The setup is straightforward on bare metal servers but becomes more complicated in cloud environments where public IPs are mapped to private virtual network addresses. While this solution works effectively for exe.dev, the authors caution that it requires custom management software and may not be suitable for broader use cases involving multiplexed SSH access.