In Service Software Upgrade (ISSU) permits administrators to upgrade the control plane software of a network device without any disruption to the traffic passing through the data plane of the network device. However, because the control plane is unavailable, the network device is unable to transmit periodic messages to re-subscribe to specific VLANs. This may result in a service outage in end devices that rely on the network device to receive data assigned to those VLANs. To prevent the network device from being unsubscribed from the VLANs while the control plane is unavailable, the network device may transmit a control plane message before starting ISSU. Once a neighboring network device receives the message, the neighboring device delays unsubscribing the network device until the control plane is again available. Thus, the network device may perform ISSU without the possibility of data traffic not reaching end devices.