AS overview
Test target: 2a0e:71c0::1 · static prefix probe · address space: PA · prefixes announced: 9
prefix(es): 2a0e:71c7::/32, 2a0e:71c5::/32, 2a0e:71c3::/32, 2a0e:71c2::/32, 2a0e:71c4::/32, 2a0e:71c0::/32, 2a0e:71c0::/29, 2a0e:71c6::/32 (+1 more)
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:71c0::1 | prb | ✓ | ✓ | ? | ? | ✓ | ✓ | ✓ | refused | refused | ✓ | ✓ | ✓ | refused | refused | ✓ |
RPKI & ASPA
9 of 9 prefix(es) covered by a valid ROA.
| Prefix | RPKI state | Reason | Covering VRP(s) |
|---|---|---|---|
2a0e:71c7::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c5::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c3::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c2::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c4::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c0::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c0::/29 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c6::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
2a0e:71c1::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS208499 /29 maxLen 32 (ripe) |
Random-IP probe (yarrp) into the AS' prefixes
At least one router inside AS208499's announced prefix replied during the random-target probe. Hop(s): 2a0e:71c0::1, 2a0e:71c0::2. 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:71c0::1 | icmp6-echo | honored | 2026-05-30T12:47:34Z |
| karsolink | 2a12:d8c0:105a:9001::a154 | 2a0e:71c0::1 | icmp6-echo | inconclusive | 2026-05-30T12:56:24Z |
| odin | 2607:fae0:a000::42 | 2a0e:71c0::1 | icmp6-echo | honored | 2026-05-30T12:47:15Z |
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): AS208499, AS41327, AS50673.
- From go6lab (open/Type-2=honored) the path enters AS41327 at hop 6; from karsolink (open/Type-2=inconclusive) the same hop is in AS208499. Last common AS: AS208499. The disagreement is most likely rooted in one of those two transit ASes.
- From go6lab (open/Type-2=honored) the path enters AS50673 at hop 3; from odin (open/Type-2=honored) the same hop is in AS56635. Last common AS: AS208499. The disagreement is most likely rooted in one of those two transit ASes.
- From karsolink (open/Type-2=inconclusive) the path enters AS208499 at hop 6; from odin (open/Type-2=honored) the same hop is in AS6939. Last common AS: AS208499. 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.
| # | hop IP | AS | Holder | PTB acceptance |
|---|---|---|---|---|
| 1 | 2607:fae0:a000::2 | AS8038 | 6CONNECT - 6connect, Inc., US | - skipped (CoPP) |
| 2 | * | - | - (no IP) | |
| 3 | 2a03:a100:0:201:1::1 | AS56635 | XENYA - XENYA inzeniring, proizvodnja in | ✓ honored |
| 4 | 2001:470:1:5be::1 | AS6939 | HURRICANE - Hurricane Electric LLC, US | ? no_response |
| 5 | * | - | - (no IP) | |
| 6 | 2001:470:0:2ea::2 | AS6939 | HURRICANE - Hurricane Electric LLC, US | ? no_response |
| 7 | * | - | - (no IP) | |
| 8 | 2001:470:0:4d4::2 | AS6939 | HURRICANE - Hurricane Electric LLC, US | ? no_response |
| 9 | 2a0e:71c0::1 | AS208499 | WIRECOM - Wirecom S.r.l., IT | ✓ honored |
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 | 1.2ms | 0% | AS203993 | STEFFANN-DC-AS - S.J.M. Steffann, NL |
| 2 | * | - | 0%* | - | |
| 3 | 2a00:1ca8:1::194 | 2.6ms | 0% | AS50673 | Serverius-as - Serverius Holding B.V., NL |
| 4 | 2a03:3f40::10:41 | 3.8ms | 0% | AS50673 | Serverius-as - Serverius Holding B.V., NL |
| 5 | speed-ix.fibertelecom.it 2001:7f8:b7::a504:1327:1 | 4.2ms | 0% | - | NA |
| 6 | 2a03:b020::228 | 28.3ms | 0% | AS41327 | FIBERTELECOM-AS - Fiber Telecom S.p.A., IT |
| 7 | 2a0e:71c0::1 | 28.4ms | 0% | AS208499 | WIRECOM - Wirecom S.r.l., IT |
tracepath -6
1?: [LOCALHOST] 0.031ms pmtu 1500
1: 2a00:8642:42::3 1.886ms
1: 2a00:8642:42::3 1.498ms
2: gw.friends.steffann.nl 2.376ms
3: 2a00:1ca8:1::194 3.050ms
4: 2a03:3f40::10:41 2.898ms
5: speed-ix.fibertelecom.it 4.560ms asymm 3
6: 2a03:b020::228 28.623ms asymm 4
7: 2a0e:71c0::1 29.243ms reached
Resume: pmtu 1500 hops 7 back 5 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 | 2a12:d8c0:109f:121::a1 | 0.5ms | 0%* | AS204471 | KARSOLINK - 2S Computers SRL, IT |
| 3 | * | - | 0% | - | |
| 4 | 2a03:b020:1:51::a | 10.2ms | 0% | AS41327 | FIBERTELECOM-AS - Fiber Telecom S.p.A., IT |
| 5 | 2a03:b020::228 | 18.2ms | 0% | AS41327 | FIBERTELECOM-AS - Fiber Telecom S.p.A., IT |
| 6 | 2a0e:71c0::1 | 18.6ms | 0% | AS208499 | WIRECOM - Wirecom S.r.l., IT |
tracepath -6
1?: [LOCALHOST] 0.028ms pmtu 1500
1: karsolink-01.net.karsolink.com 0.504ms
1: karsolink-01.net.karsolink.com 0.486ms
2: 2a12:d8c0:109f:121::a1 0.743ms
3: 2a12:d8c0:101f:6::1 10.546ms
4: 2a03:b020:1:51::a 10.665ms
5: 2a03:b020::228 19.075ms
6: 2a0e:71c0::1 19.662ms reached
Resume: pmtu 1500 hops 6 back 6 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 | 0.3ms | 0%* | AS8038 | 6CONNECT - 6connect, Inc., US |
| 2 | * | - | - | - | |
| 3 | 2a03:a100:0:201:1::1 | 0.5ms | 0% | AS56635 | XENYA - XENYA inzeniring, proizvodnja in trgovina, d.o.o. Ljubljana, SI |
| 4 | e0-1.core1.lju1.he.net 2001:470:1:5be::1 | 1.9ms | 0% | AS6939 | HURRICANE - Hurricane Electric LLC, US |
| 5 | * | - | - | - | |
| 6 | port-channel1.core1.zag2.he.net 2001:470:0:2ea::2 | 4.1ms | 0% | AS6939 | HURRICANE - Hurricane Electric LLC, US |
| 7 | * | - | - | - | |
| 8 | e0-36.core2.rom1.he.net 2001:470:0:4d4::2 | 20.8ms | 0% | AS6939 | HURRICANE - Hurricane Electric LLC, US |
| 9 | 2a0e:71c0::1 | 19.0ms | 0% | AS208499 | WIRECOM - Wirecom S.r.l., IT |
tracepath -6
1?: [LOCALHOST] 0.077ms pmtu 1500
1: fw1-lju.6connect.com 0.554ms
1: fw1-lju.6connect.com 0.478ms
2: no reply
3: 2a03:a100:0:201:1::1 2.044ms
4: e0-1.core1.lju1.he.net 2.023ms
5: no reply
6: no reply
7: no reply
8: e0-36.core2.rom1.he.net 21.314ms
9: 2a0e:71c0::1 19.028ms reached
Resume: pmtu 1500 hops 9 back 6