An HTTP check from Belgrade (AS51430) sends a complete GET request including DNS resolution, TCP handshake, TLS negotiation, and measures time to first byte. For CDN-hosted services, the AltusHost source IP will determine which edge PoP is selected. Most CDN providers classify Serbian IPs under Balkans or Eastern Europe and route to Vienna, Frankfurt, or a local Belgrade edge if one exists. Cloudflare has a Belgrade presence, so Cloudflare-proxied sites typically resolve to a nearby edge from this node.

HTTP response times from Belgrade for a Cloudflare-cached resource should be under 30–40 ms if the Belgrade PoP is selected. For an uncached origin in Frankfurt, expect total response times of 90–130 ms for a small HTML page including TLS. Origins in Vienna will come in around 60–80 ms total. If you see consistently higher response times than these baselines, the CDN is likely routing Serbia to a non-local PoP, or TLS session resumption is not functioning correctly.

A non-200 response specifically from our Serbian node while other Central European nodes succeed may indicate IP reputation filtering, WAF rules covering Serbian address space, or geo-blocking. AS51430 is a legitimate European hosting ASN registered in the Netherlands and should not trigger most commercial security products. If you observe blocking, compare against our Bulgarian and Hungarian nodes to determine whether the restriction targets Serbian IPs specifically or a broader Eastern European range.

Belgrade is the largest network hub in the Western Balkans. SIX (Serbian Internet Exchange), hosted at Telehouse Belgrade, is the primary domestic peering point and a RIPE NCC member. It connects Serbian ISPs, regional carriers, and CDN providers, and its presence in Telehouse makes it co-located with a significant portion of Serbia's colocation market. Our probe node runs on AS51430 (AltusHost B.V.) in Belgrade, a provider with EU-wide hosting operations and strong regional BGP peering.

Serbia sits at a geographic crossroads between Central and Southeastern Europe, with good terrestrial transit connectivity in multiple directions. Belgrade-to-Budapest runs approximately 18–22 ms, Belgrade-to-Sofia approximately 13–17 ms, Belgrade-to-Vienna approximately 28–34 ms, and Belgrade-to-Zagreb approximately 10–14 ms. This central Balkan position means Serbian-hosted infrastructure is within low-latency reach of Hungary, Bulgaria, Romania, Croatia, and Bosnia simultaneously — making Belgrade a practical regional origin for Balkan-facing services.

The Serbian ISP market is anchored by Telekom Srbija (AS8400), which operates the national backbone and holds the largest fixed-line subscriber base. Serbia Broadband (SBB, AS31042) serves the commercial and cable market. Telenor Serbia and Yettel operate mobile and broadband networks. On the hosting and transit side, AltusHost (AS51430), Veesp, and several regional providers operate colocation in Belgrade. Transit upstream for Serbian networks typically routes through RETN (AS9002), Cogent (AS174), Level3/Lumen (AS3356), and Telekom Srbija's own international transit.

Belgrade's Telehouse data center is the primary carrier-neutral facility in Serbia and acts as the physical interconnect hub for most carrier peering in the country. SIX operates within Telehouse, giving colocation customers at that facility direct access to the IX fabric without additional cross-connects. Several international CDN providers, including Cloudflare and Akamai, have edge nodes in or around Belgrade, which measurably improves response times for Serbian users accessing major content platforms versus routing to Vienna or Frankfurt.

AltusHost (AS51430) has a broader EU footprint beyond Belgrade, with presence in the Netherlands and other markets, which means its BGP routing is more sophisticated than a purely local ISP. Results from our Belgrade node on AS51430 will reflect the routing decisions of a commercially-oriented hosting provider with multiple upstream transit providers rather than the residential or national-backbone routing that Telekom Srbija would show. For checks targeting international infrastructure, this is generally the more relevant probe for professional use cases.