Due to the increased complexity of new in-vehicle networking architectures, which makes direct monitoring of internal network components intractable, alternative solutions are required to tackle this issue. One solution is to leverage the end-to-end measurements to estimate the internal network performance. To this end, we propose to employ network tomography as a monitoring approach for in-vehicle networks. Network tomography can infer the overall network performance by measuring only subset of the network. We investigate the use of network tomography in in-vehicle network by analysing network identifiability of three main architectures: bus-based, central-gateway, and Ethernet-based architectures. Our analysis results indicate the applicability of network tomography in in-vehicle networks based on certain topological and monitors' conditions. Furthermore, we validate our analytical results through simulation which shows a maximum error of only $174\mu s$. Moreover, we compare the proposed approach with one of existing solutions and show that network tomography achieves better bandwidth and latency performance with monitoring overhead saving up to 52.2% and $782.3\mu s$, respectively.