A computer-implemented method comprising: launching, by a provider substrate extension of a cloud provider network, a compute instance on the provider substrate extension of the cloud provider network, wherein the provider substrate extension is deployed within a site of a first communications service provider, CSP, network and comprises one or more servers configured to communicate over a network with a substrate of the cloud provider network, the substrate comprising hardware configured to run services of the cloud provider network, wherein the site implements at least a part of the first CSP network, wherein the provider substrate extension is communicatively coupled between the mobile core network of the first CSP network and an internet exchange point, IXP, wherein an edge of a second CSP network exists at the IXP, and wherein the provider substrate extension is managed at least in part by a control plane service of the cloud provider network; causing, by a gateway of the provider substrate extension, a first route associated with the compute instance to be advertised to the first CSP network; causing, by the gateway, a second route associated with the compute instance to be advertised to the second CSP network, that is peered with at least a portion of the first CSP network; receiving, by the gateway, a first set of packets originated by a first one or more user equipment, UE, devices, the first set of packets having been sent through one or more transport networks via a tunnel of a mobile overlay network of the first CSP network, exited the tunnel at the mobile core network, and routed to the provider substrate extension via the first CSP network in accordance with the first route; receiving, by the gateway, a second set of packets originated by a second one or more UE devices and routed to the provider substrate extension via the second CSP network through the IXP in accordance with the second route; and forwarding, by the gateway to the compute instance, the first set of packets and the second set of packets. launching, by a provider substrate extension of a cloud provider network, a compute instance on the provider substrate extension of the cloud provider network, wherein the provider substrate extension is deployed within a site of a first communications service provider, CSP, network and comprises one or more servers configured to communicate over a network with a substrate of the cloud provider network, the substrate comprising hardware configured to run services of the cloud provider network, wherein the site implements at least a part of the first CSP network, wherein the provider substrate extension is communicatively coupled between the mobile core network of the first CSP network and an internet exchange point, IXP, wherein an edge of a second CSP network exists at the IXP, and wherein the provider substrate extension is managed at least in part by a control plane service of the cloud provider network; wherein the provider substrate extension is deployed within a site of a first communications service provider, CSP, network and comprises one or more servers configured to communicate over a network with a substrate of the cloud provider network, the substrate comprising hardware configured to run services of the cloud provider network, wherein the site implements at least a part of the first CSP network, wherein the provider substrate extension is communicatively coupled between the mobile core network of the first CSP network and an internet exchange point, IXP, wherein an edge of a second CSP network exists at the IXP, and wherein the provider substrate extension is managed at least in part by a control plane service of the cloud provider network; causing, by a gateway of the provider substrate extension, a first route associated with the compute instance to be advertised to the first CSP network; causing, by the gateway, a second route associated with the compute instance to be advertised to the second CSP network, that is peered with at least a portion of the first CSP network; receiving, by the gateway, a first set of packets originated by a first one or more user equipment, UE, devices, the first set of packets having been sent through one or more transport networks via a tunnel of a mobile overlay network of the first CSP network, exited the tunnel at the mobile core network, and routed to the provider substrate extension via the first CSP network in accordance with the first route; receiving, by the gateway, a second set of packets originated by a second one or more UE devices and routed to the provider substrate extension via the second CSP network through the IXP in accordance with the second route; and forwarding, by the gateway to the compute instance, the first set of packets and the second set of packets.