AS overview
Test target: 2a0e:8f02:f026::1 · static prefix probe · address space: unknown · prefixes announced: 1
prefix(es): 2a0e:8f02:f026::/48
Targets & per-vantage-point probe results (1 target(s) across 3 vantage point(s))
Source codes (hover any badge for full description): CUR=curated · NS/SOA/MX=DNS records · SPF=SPF TXT · DRV=holder-derived (www, ns1, mail, gw, …) · ATL=RIPE Atlas · PDB=PeeringDB · WHOIS=RIPE whois · RDAP=RIPE RDAP · HIT=IPv6 Hitlist · RTR=in-prefix path hop (router) · PRB=static prefix probe · SYN=synthetic prefix::1 fallback
| Target IP / hostname | Source | NL host (go6lab) | ITA host (Karsolink) | SLO host (6connect) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ping | 1500B | :80 | :443 | reached | ping | 1500B | :80 | :443 | reached | ping | 1500B | :80 | :443 | reached | ||
2a0e:8f02:f026::1 | prb | ✓ | ✓ | ? | ? | ✓ | ✓ | ✓ | refused | refused | ✓ | ✓ | ✓ | refused | refused | ✓ |
RPKI & ASPA
0 of 1 prefix(es) covered by a valid ROA, 1 not-found.
| Prefix | RPKI state | Reason | Covering VRP(s) |
|---|---|---|---|
2a0e:8f02:f026::/48 | - not-found | no covering VRP |
Random-IP probe (yarrp) into the AS' prefixes
At least one router inside AS211480's announced prefix replied during the random-target probe. Hop(s): 2a0e:8f02:f026::1. These are candidate targets for direct testing.
ICMPv6 Type 2 (Packet Too Big) acceptance - active test
Vantage points disagree about Type 2 acceptance - transit ASes on one path may be filtering Type 2 even though the destination's stack accepts it on another path:
- NL host (go6lab): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
- ITA host (Karsolink): inconclusive: no Echo Reply after PTB (probe 1500B). (ICMPv6 Echo + forged PTB)
- SLO host (6connect): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
Why they disagree - measurement artifact: One vantage's probe didn't generate enough data to detect segment shrinkage (natural reply too small, or no second response). The other vantage's verdict is the meaningful one.
Failure detail — what to grep in your logs
| vantage | our source | your target | method | result | tested (UTC) |
|---|---|---|---|---|---|
| go6lab | 2a00:8642:42::75 | 2a0e:8f02:f026::1 | icmp6-echo | honored | 2026-05-30T12:47:35Z |
| karsolink | 2a12:d8c0:105a:9001::a154 | 2a0e:8f02:f026::1 | icmp6-echo | inconclusive | 2026-05-30T12:56:27Z |
| odin | 2607:fae0:a000::42 | 2a0e:8f02:f026::1 | icmp6-echo | honored | 2026-05-30T12:47:16Z |
Attempt log (go6lab):
icmp6-echo→ honored (size_before=1460, size_after=None)dns-tcp→ no_tcp: connect failed: timed outtls→ no_tcp: TLS connect failedhttp→ no_tcp: tcp/80 not open
Attempt log (karsolink):
icmp6-echo→ inconclusive (size_before=1460, size_after=None): no Echo Reply after PTB (probe 1500B)dns-tcp→ no_tcp: connect failed: [Errno 111] Connection refusedtls→ no_tcp: TLS connect failedhttp→ no_tcp: tcp/80 not open
Attempt log (odin):
icmp6-echo→ honored (size_before=1460, size_after=None)dns-tcp→ no_tcp: connect failed: [Errno 111] Connection refusedtls→ no_tcp: TLS connect failedhttp→ no_tcp: tcp/80 not open
To match the corresponding ICMPv6 packet on your side (host firewall, AS edge, or transit tap), look for our PTBs around the timestamps above:
sudo tcpdump -i any -n -e 'icmp6 and ip6[40] = 2 and (src host 2607:fae0:a000::42 or src host 2a00:8642:42::75 or src host 2a12:d8c0:105a:9001::a154)'
If you see our PTBs arriving but the destination's TCP/Echo flow does not shrink, the drop is in the destination kernel (cause 3 below). If you don't see them at all, drop is upstream of you (cause 2). If you only see them from one of our two source IPs, the drop is path-asymmetric — one transit on the asymmetric route is filtering, the other is not.
Where the path divergence is
Per-vantage probe + verdict (headline):
- go6lab: probe
icmp6-echo→ verdicthonored - karsolink: probe
icmp6-echo→ verdictinconclusive - odin: probe
icmp6-echo→ verdicthonored
Full per-method matrix (all four methods run at each vantage):
| vantage | icmp6-echo | dns-tcp | tls | http |
|---|---|---|---|---|
| go6lab | honored | no_tcp | no_tcp | no_tcp |
| karsolink | inconclusive | no_tcp | no_tcp | no_tcp |
| odin | honored | no_tcp | no_tcp | no_tcp |
✓ All vantages agree on method(s): icmp6-echo — the headline-method spread above is dispatcher noise, not a real Type 2 disagreement.
These vantage-level disagreements are rooted somewhere in the forward paths. Joining each per-vantage traceroute against the IP→AS lookup from our global yarrp mesh, the first hop where the paths land in different ASes is the most likely site of the offending filter / unreachable AS / Type 2 drop.
Suspect transit ASes (ranked by how often they appear at the divergence point on the path of the worse-classifying vantage): AS34927, AS5603, AS211480.
- From go6lab (open/Type-2=honored) the path enters AS211480 at hop 5; from karsolink (open/Type-2=inconclusive) the same hop is in AS34927. Last common AS: AS211480. The disagreement is most likely rooted in one of those two transit ASes.
- From go6lab (open/Type-2=honored) the path enters AS34927 at hop 3; from odin (open/Type-2=honored) the same hop is in AS5603. Last common AS: AS211480. The disagreement is most likely rooted in one of those two transit ASes.
- From karsolink (open/Type-2=inconclusive) the path enters AS34927 at hop 4; from odin (open/Type-2=honored) the same hop is in AS5603. Last common AS: AS211480. The disagreement is most likely rooted in one of those two transit ASes.
Diagnosis is path-level, not packet-level: it tells you which transit AS is the prime suspect, not exactly which firewall rule is to blame. Use the tracepath6 output below (when available) for per-hop PMTU evidence on the same path.
✨ Diagnostic interpretation
Per-hop PTB acceptance walk
From the local vantage, we walk the forward path hop-by-hop, sending each hop a 1500-byte ICMPv6 Echo, then a forged PTB (MTU=1280) sourced from us, then another 1500-byte Echo. If the second reply arrives fragmented or smaller, that hop honoured the PTB. If unchanged, it didn't. The first ✗ in an otherwise-✓ path is the most likely filter location. Cross-country aggregation: see the global PTB filter atlas for transit ASes ranked by filter rate across all measurements.
First break at hop 3: AS5603 (SIOL-NET - Telekom Slovenije, d.d., SI) -- this is the most likely site of the offending PTB filter. Hop IP: 2a00:ee1:800:9::1.
| # | hop IP | AS | Holder | PTB acceptance |
|---|---|---|---|---|
| 1 | 2607:fae0:a000::2 | AS8038 | 6CONNECT - 6connect, Inc., US | - skipped (CoPP) |
| 2 | * | - | - (no IP) | |
| 3 | 2a00:ee1:800:9::1 | AS5603 | SIOL-NET - Telekom Slovenije, d.d., SI | ✗ not_honored |
| 4 | 2a00:ee0:1:10::2 | AS5603 | SIOL-NET - Telekom Slovenije, d.d., SI | ✗ not_honored |
| 5 | 2a0c:9a40:1001::1 | AS34927 | iFog-GmbH - iFog GmbH, CH | ✓ honored |
| 6 | 2a0e:8f02:f026::1 | AS211480 | SAMI-AS - Sami Yessou, IT | ? no_response |
Tests host-mode PTB acceptance (PTBs aimed at the hop itself). A router that honours PTBs to itself can still be filtering PTBs transiting through it; this is one indicator, not proof of full PTB transparency. Hops in CoPP-rate-limit ranges are skipped to avoid false signals.
From NL host (go6lab) openRFC 4890 ✓
filter likely at: (none) · min PMTU on path: 1500
Path (traceroute + mtr + PTR)
| # | IP / PTR | RTT | mtr loss | AS | AS holder |
|---|---|---|---|---|---|
| 1 | 2a00:8642:42::3 | 1.3ms | 0% | AS203993 | STEFFANN-DC-AS - S.J.M. Steffann, NL |
| 2 | gw.friends.steffann.nl 2a00:8642:1000:f000::1 | 2.1ms | 0%* | AS203993 | STEFFANN-DC-AS - S.J.M. Steffann, NL |
| 3 | 2a0c:9a40:1071::1 | 4.2ms | 0% | AS34927 | iFog-GmbH - iFog GmbH, CH |
| 4 | 2a0c:9a40:1001::1 | 10.5ms | 0% | AS34927 | iFog-GmbH - iFog GmbH, CH |
| 5 | 2a0e:8f02:f026::1 | 10.6ms | 10% | AS211480 | SAMI-AS - Sami Yessou, IT |
Rate-limited ICMPv6: hop 5 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).
tracepath -6
1?: [LOCALHOST] 0.028ms pmtu 1500
1: 2a00:8642:42::3 1.866ms
1: 2a00:8642:42::3 1.668ms
2: gw.friends.steffann.nl 2.795ms
3: 2a0c:9a40:1071::1 3.522ms
4: 2a0c:9a40:1001::1 11.119ms asymm 5
5: ??? 11.815ms reached
Resume: pmtu 1500 hops 5 back 6 From ITA host (Karsolink) open
filter likely at: (none) · min PMTU on path: 1500
Path (traceroute + mtr + PTR)
| # | IP / PTR | RTT | mtr loss | AS | AS holder |
|---|---|---|---|---|---|
| 1 | * | - | 0%* | - | |
| 2 | * | - | 0%* | - | |
| 3 | 2a12:d8c0:101f:6::1 | 10.0ms | 0% | AS204471 | KARSOLINK - 2S Computers SRL, IT |
| 4 | 2a0c:9a40:3000::1 | 9.9ms | 0% | AS34927 | iFog-GmbH - iFog GmbH, CH |
| 5 | 2a0c:9a40:1092::1 | 12.6ms | 0% | AS34927 | iFog-GmbH - iFog GmbH, CH |
| 6 | 2a0e:8f02:f026::1 | 12.5ms | 0% | AS211480 | SAMI-AS - Sami Yessou, IT |
tracepath -6
1?: [LOCALHOST] 0.028ms pmtu 1500
1: karsolink-01.net.karsolink.com 0.894ms
1: karsolink-01.net.karsolink.com 1.094ms
2: no reply
3: 2a12:d8c0:101f:6::1 10.555ms
4: 2a0c:9a40:3000::1 10.678ms
5: 2a0c:9a40:1092::1 13.264ms asymm 7
6: ??? 13.580ms reached
Resume: pmtu 1500 hops 6 back 8 From SLO host (6connect) openRFC 4890 ✓
filter likely at: (none) · min PMTU on path: 1500
Path (traceroute + mtr + PTR)
| # | IP / PTR | RTT | mtr loss | AS | AS holder |
|---|---|---|---|---|---|
| 1 | fw1-lju.6connect.com 2607:fae0:a000::2 | 0.2ms | 0%* | AS8038 | 6CONNECT - 6connect, Inc., US |
| 2 | * | - | - | - | |
| 3 | 2a00:ee1:800:9::1 | 1.7ms | 0% | AS5603 | SIOL-NET - Telekom Slovenije, d.d., SI |
| 4 | 2a00:ee0:1:10::2 | 1.2ms | 0% | AS5603 | SIOL-NET - Telekom Slovenije, d.d., SI |
| 5 | 2a0c:9a40:1001::1 | 33.6ms | 0% | AS34927 | iFog-GmbH - iFog GmbH, CH |
| 6 | 2a0e:8f02:f026::1 | 33.8ms | 0% | AS211480 | SAMI-AS - Sami Yessou, IT |
tracepath -6
1?: [LOCALHOST] 0.033ms pmtu 1500
1: fw1-lju.6connect.com 0.578ms
1: fw1-lju.6connect.com 0.353ms
2: no reply
3: 2a00:ee1:800:9::1 2.158ms
4: 2a00:ee0:1:10::2 1.095ms asymm 3
5: 2a0c:9a40:1001::1 33.977ms asymm 9
6: ??? 34.482ms reached
Resume: pmtu 1500 hops 6 back 10