AS inventory
Slovenia has 271 autonomous systems registered with the RIR. Of those, 259 (96 %) currently announce at least one IPv4 prefix to the global routing table, and 78 (29 %) currently announce at least one IPv6 prefix. That means 30 % of the IPv4-active ASes have followed through and turned on IPv6.
Operators - PA (Provider Aggregatable) holders
PA-holding ASes are LIRs with their own RIR allocation - they are the operators running parts of Slovenia’s internet (transits, ISPs, content networks with infrastructure of their own). Slovenia has 76 PA-holding operator ASes registered with the RIR. Of those, 72 (95 %) announce IPv4 today and 43 (57 %) announce IPv6.
End-sites - PI (Provider Independent) holders
PI-holding ASes hold address space directly from the RIR for their own use - typically enterprises, content sites running their own AS for routing diversity, government / academic single-site deployments. They’re not “operators” in the LIR sense, but they show up in BGP and their v6 readiness still matters. Slovenia has 182 PI-holding end-site ASes. Of those, 179 (98 %) announce IPv4 and 25 (14 %) announce IPv6.
Country totals: 271 routed ASes / 259 announce IPv4 / 78 announce IPv6. 11 ASes are unclassified (RIPE inet*num lookup didn’t return a clear status). PA / PI counts above include the “mixed” bucket on the PA side since a mixed AS holds at least one PA prefix and operationally functions as an LIR.
Executive summary
We measure how 78 Slovenian autonomous systems that announce 182 IPv6 prefix(es) treat ICMPv6 in practice - Echo, Type 2 (Packet Too Big), Time-Exceeded - using three ICMPv6 vantage points and a 12-node global yarrp mesh, plus the SIX route-server BGP table as ground truth. Generated 2026-05-30 10:57 UTC.
Adoption
According to RIPEstat, 78 ASes registered to Slovenia announce at least one IPv6 prefix to the global routing table, advertising 182 distinct prefixes between them. The 12-vantage-point mesh observed 119 distinct ASes (Slovenian + foreign transits) and 260 AS-AS adjacencies along paths into Slovenia.
ICMPv6 behaviour at the destination
Each AS gets a single classification per vantage point by combining the small Echo, the 1500-byte Echo with DF set, traceroute reachability, and a TCP liveness check. Aggregated across all 3 vantage points, the SLO population looks like this:
- open - 58 ASes (74%)
- echo only - 3 ASes (4%)
The open bucket means every vantage point received Echo Replies for both small and 1500-byte probes; this is what every SLO network should look like. echo_only means small ping passed but 1500-byte packets did not - usually either a path-MTU constraint downstream of us, or a real ICMPv6 Type 2 (Packet Too Big) filter en route. The two unreachable buckets cover ASes whose AS edge filters all incoming ICMPv6.
Weekly-probe schedule: 17 of SLO’s 95 IPv6-announcing ASes are on a 6-day probe cycle today because they’ve produced a stably-unreachable / no-host result for 14+ consecutive daily runs. Today’s numbers reflect the 78 ASes probed this run; the skipped 17 are re-tested approximately weekly. (Tuneable in scripts/19_update_skip_list.py -- raise STREAK_TO_SKIP to probe more aggressively, lower WEEKLY_PROBE_DAYS to re-test sooner.)
RFC 4890 compliance (active Type 2 test)
RFC 4890 gives operators the option to drop ICMPv6 Echo at the firewall, but says Type 2 (Packet Too Big) must remain permitted end-to-end - otherwise PMTUD is broken and large flows hang silently. We test this directly: for every reachable AS we open an active flow (TCP/53 DNS, TCP/443 TLS, ICMPv6 Echo, or HTTP/80 - whichever applies), forge an ICMPv6 Type 2 with MTU=1280, and observe whether the destination acts on it.
- RFC 4890 ✓ - 53 ASes proven compliant: AS2107, AS3212, AS5435, AS9119, AS12778, AS21283
- RFC 4890 ✗ - 5 ASes proven non-compliant (PMTUD will break for users): AS24629, AS25303, AS43128, AS43351, AS199971
- The remaining 3 are unknown - typically because their network blocks Echo entirely (we cannot directly probe Type 2 acceptance from outside) or because the active test was inconclusive on this run.
Active-test method breakdown across all targets: honored = 539, no_echo = 285, not_honored = 115, inconclusive = 32, partial = 12, no_tcp = 11.
SIX peering
The Slovenian Internet Exchange (SIX) currently has 38 peering members reachable via its route servers. Of those, 23 are Slovenian-registered ASes; the rest are international peers that serve Slovenian traffic via SIX (common examples: Hurricane Electric, Cloudflare, PCH).
Top SIX-internal transit relationships (BGP-truth)
For the full members list with live route-server session state, see the dedicated SIX page.
Path-MTU and Type 2 evidence
The active Type 2 test produced definitive verdicts for 85 unique destination IP addresses across vantage points.
- Honored (destination accepted our forged Packet-Too-Big and shrank its next response): 56 ASes - AS2107, AS3212, AS5435, AS5603, AS9119, AS12778, AS21283, AS25173 (+48 more)
- Not honored (destination ignored the PTB or the PTB was filtered en route): 29 ASes - AS2107, AS3212, AS5603, AS9119, AS21283, AS24629, AS25303, AS25467 (+21 more)
Global BGP visibility (RIPE RIS)
For every SLO prefix we asked all RIPE RIS collectors what AS-paths they currently see. That gives us each AS' direct upstream(s) according to the global BGP table.
RPKI & ASPA
RPKI ROAs cryptographically bind a prefix to its origin AS, so route-leaks and
hijacks of that prefix can be filtered. We validate every announced SLO IPv6 prefix
against the local Routinator (rpki-lju.6connect.com).
Of 78 SLO ASes announcing IPv6:
- 55 (71%%) have at least one valid ROA
- 49 (63%%) have all their IPv6 prefixes covered by valid ROAs
- 23 (29%%) have not signed any of their prefixes
- 1 have at least one invalid prefix (origin or maxLength mismatch)
Per prefix: 142 valid, 1 invalid, 39 not-found (of 182 total).
RPKI-invalid prefixes
- AS197209 STN-EU-AS STN STORITVE d.o.o. -
2a00:ee7::/48: prefix is covered by VRP(s) for different origin AS(es): AS5603
Top unsigned ASes (no ROAs)
- AS6764 PERFTECH-SLOVENIA-AS PERFTECH, podjetje za proizvodnjo in uvajanje novih tehnologij, d.o.o. (1 prefix)
- AS24629 NIL-AS NIL Data Communications Ltd. (1 prefix)
- AS25303 KDD KDD d.d. (1 prefix)
- AS41104 PODRAVKA-AS PODRAVKA trgovsko podjetje, d.o.o. Ljubljana (1 prefix)
- AS41427 marc-net_AS Datacenter d.o.o. (1 prefix)
- AS44993 MOBIK-AS Mobik d.o.o. (1 prefix)
- AS47917 RTVSLO-ASN RTV Slovenija (1 prefix)
- AS50344 SI-CDE-IT CDE IT, informacijske resitve d.o.o. (1 prefix)
- AS51509 NEO-AS NEO IT d.o.o. (1 prefix)
- AS56993 KZPS KONTROLA ZRACNEGA PROMETA SLOVENIJE, d.o.o. (1 prefix)
- AS57517 POLICIJA-AS Ministrstvo za notranje zadeve (1 prefix)
- AS57532 KTVRavne Kabelska televizija Ravne d.o.o. (1 prefix)
- AS58046 HKOM-AS The Ministry of Digital Transformation (1 prefix)
- AS62255 BEMYLINK BiMajLink d.o.o. (1 prefix)
- AS198827 ELEKTROGORENJSKA-SI Elektro Gorenjska, podjetje za distribucijo elektricne energije, d.d. (1 prefix)
ASPA (Autonomous System Provider Authorization)
ASPA is a much newer (RFC 9774) RPKI object: it lets a customer AS list which upstream providers may legitimately propagate routes from it. Routes from that AS arriving via any other path are then ASPA-invalid.
10 of 78 SLO ASes have published an ASPA record:
- AS12778 SGN MEGA M, d.o.o. - provider(s): AS174, AS3356, AS5511, AS44306
- AS41828 TELEMACH-HOSTING Telemach Slovenija d.o.o. - provider(s): AS3212
- AS44549 MEGA-M-AS MEGA M, d.o.o. - provider(s): AS12778
- AS56635 XENYA XENYA inzeniring, proizvodnja in trgovina, d.o.o. Ljubljana - provider(s): AS3212, AS6939, AS12778, AS198524
- AS197579 BASS-SI BASS d.o.o., Celje - provider(s): AS3212, AS12778, AS34779, AS214499
- AS198524 ILOL iLOL d.o.o. - provider(s): AS174, AS6939, AS12778, AS21283, AS44306, AS56635
- AS200325 BunnyCDN BUNNYWAY, informacijske storitve d.o.o. - provider(s): AS174, AS3491, AS4229, AS7195, AS8849, AS9009, AS12186, AS18450, AS20326, AS20473, AS21859, AS36236, AS40994, AS49544, AS51095, AS56630, AS60068, AS61317, AS136557, AS137409, AS199524
- AS204471 KARSOLINK 2S Computers SRL - provider(s): AS9002, AS41327, AS50877, AS62275
- AS210715 PISKOT-AS Nik Rozman - provider(s): AS209533, AS212895
- AS214499 BASS-2 BASS d.o.o., Celje - provider(s): AS5603, AS197579
Path asymmetry
For every SLO AS we compared where our outgoing traffic enters their network (the AS just upstream of them on traceroute paths from any of our 14 vantage points) to which AS the global BGP table says is their direct upstream (RIS view). When these disagree, the network is multi-homed and traffic in vs. out takes different paths - normal in well-peered networks but worth surfacing.
52 SLO ASes flagged as asymmetric this run. Most asymmetric examples (low symmetry score):
- AS60435 HUMANFROG-AS Humanfrog d.o.o. - symmetry score 0.00; RIS sees upstreams [AS28682] but our paths went via [AS56635].
- AS200325 BunnyCDN BUNNYWAY, informacijske storitve d.o.o. - symmetry score 0.00; RIS sees upstreams [AS3491, AS4229, AS7195, AS12186] but our paths went via [AS174, AS2914].
- AS28933 LTFE-AS University of Ljubljana, Faculty of Electrical Engineering - symmetry score 0.00; RIS sees upstreams [AS5603] but our paths went via [AS2107].
- AS210715 PISKOT-AS Nik Rozman - symmetry score 0.00; RIS sees upstreams [AS209533, AS212895] but our paths went via [AS34927].
- AS25467 AKTON-AS Akton d.o.o. - symmetry score 0.00; RIS sees upstreams [AS174, AS3303, AS5405, AS6939] but our paths went via [AS1299].
- AS9119 SOFTNET-AS SOFTNET d.o.o. - symmetry score 0.05; RIS sees upstreams [AS6461, AS6939, AS8218, AS9002] but our paths went via [AS51988, AS56635, AS203993, AS204471].
- AS62255 BEMYLINK BiMajLink d.o.o. - symmetry score 0.06; RIS sees upstreams [AS1299, AS5405, AS6939, AS8218] but our paths went via [AS5603, AS41327, AS50673].
- AS21283 A1SI-AS A1 Slovenija telekomunikacijske storitve,d.d. - symmetry score 0.10; RIS sees upstreams [AS3212, AS3303, AS6939, AS14840] but our paths went via [AS56635].
Bottom line
- 74% of SLO IPv6 networks accept ICMPv6 Echo unrestricted from external probes.
- 0% of SLO IPv6 networks drop all ICMPv6 at their AS edge - a meaningful fraction of the SLO population that some traffic types may struggle to debug against.
- Of the 58 ASes where our active Type 2 test reached a verdict, 53 (91%) proved RFC 4890-compliant. The rest break PMTUD for any flow that needs a smaller path-MTU than 1500.
- The SIX route servers carry the BGP-truth backbone of Slovenian IPv6: transit relationships visible on rs1 and rs2 today, with the country's largest ISPs dominating the inbound transit graph and a long tail of small ISPs and one-AS enterprises forming the customer base.
This report is regenerated daily at 12:00 Europe/Ljubljana from
data/analyzed.json, data/six_lg.json, data/global_topology.json,
data/ris_bgp.json, data/asymmetry.json and data/type2_results_<vantage>.json.
The text is deterministic - no manual editorial pass.