Recent trend shows that Internet service providers (ISPs) extensively deploy content delivery networks (CDNs) in their infrastructure to better utilize their network resources and to generate a new source of revenue. This ’telco CDN’ is attractive especially because the ISP may use their own topology and real-time traffic information to address the bottlenecks, and find a near-optimal path to deliver the content to the users. However, one challenge is that the location of telco CDN cache is limited to their ISP region, which makes it difficult to bring performance benefit to the users outside of the ISP and leads to suboptimal traffic reduction at ISP borders.CDN interconnection (CDNi) is an emerging technology that potentially eliminates the redundant HTTP traffic served from external CDNs. By temporarily caching the content owned by a collaborating peer CDN, a telco CDN can reduce the CDN traffic that crosses the ISP border while delivering the content fast to their users from its local cache. In this work, we analyze the effectiveness of CDNi in the fast-growing cellular Internet traffic. We have collected 7.7 billion HTTP logs (290 TBs by the byte volume) for a week at one of the largest cellular ISPs in South Korea and simulate the CDNi protocol to gauge the bandwidth savings as well as request redirection overheads. We see that 69% of total downlink traffic passes the Internet Exchange point (IXP), and our cache simulation reveals that 16.2% to 29% of the IXP traffic can be removed by serving it from an intra-ISP CDN with CDNi. We also find that the CDNi request redirection overhead could be significant to small objects, but we still expect a large bandwidth savings even if we redirect only large HTTP objects.