AS overview
Test target: 2a06:c180:2::face · (external source) · address space: mixed · prefixes announced: 1
prefix(es): 2a06:c180::/29
Targets & per-vantage-point probe results (7 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 | ||
2a06:c180:2::1 | hit | ✓ | ✓ | ? | ? | - | ✓ | ✓ | ? | ? | - | ✓ | ✓ | ? | ? | - |
2a06:c180:2::face | atl | ✓ | ✓ | ? | ? | ✓ | ✓ | ✓ | ? | ? | ✓ | ✓ | ✓ | ? | ? | ✓ |
2a06:c180::1 | prb | ✓ | ✓ | ? | ? | - | ✓ | ✓ | refused | refused | - | ✓ | ✓ | refused | refused | ✓ |
2a06:c180::10 | hit | ✓ | ✓ | ? | ? | - | ✓ | ✓ | ? | ? | - | ✓ | ✓ | ? | ? | - |
2a06:c180::2 | hit | ✓ | ✓ | ? | ? | ✓ | ✓ | ✓ | refused | refused | ✓ | ✓ | ✓ | refused | refused | - |
2a06:c182:1::1 | hit | ✓ | ✓ | ? | ? | - | ✓ | ✓ | refused | refused | - | ✓ | ✓ | refused | refused | - |
2a06:c182:1::2 | hit | ✓ | ✓ | ? | ? | - | ✓ | ✓ | refused | refused | - | ✓ | ✓ | refused | refused | - |
SIX peering
SIX member - open peering, peering member, since 2007-02-06. IPv6 LAN: 2001:7f8:46:0:1:0:4:4549. Locations: lj_tpl.
- rs1-lan1-ipv6 →
2001:7f8:46:0:1:0:4:4549Established (loc: lj_tpl, since 2026-05-11) - rs2-lan1-ipv6 →
2001:7f8:46:0:1:0:4:4549Established (loc: lj_tpl, since 2026-05-12)
Announces via SIX route servers: 1 prefix(es) - 2a06:c180::/29
RPKI & ASPA
1 of 1 prefix(es) covered by a valid ROA.
| Prefix | RPKI state | Reason | Covering VRP(s) |
|---|---|---|---|
2a06:c180::/29 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS44549 /29 maxLen 29 (ripe); AS12778 /29 maxLen 32 (ripe) |
ASPA: this AS has published an ASPA record listing 1 upstream provider(s) that are authorized to propagate routes from it: AS12778. Routes from this AS that arrive via any other upstream are considered ASPA-invalid by validators that enforce ASPA.
Random-IP probe (yarrp) into the AS' prefixes
We probed 15 arbitrary IPv6 address(es) inside AS44549's announced prefix(es). No router inside the prefix responded. The deepest visible hop was 2a02:d68:c:100e::2 at hop 17 - that router answers ICMPv6 Echo. This is not in AS44549's announced prefix; operationally it's the AS-edge / peering interface (often on a SIX peering address or an upstream's /127 link). The traceroute boundary is the AS edge: ICMPv6 Time-Exceeded responses from anything inside this AS are filtered.
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 | 2a06:c180:2::face | icmp6-echo | honored | 2026-05-30T10:35:25Z |
| karsolink | 2a12:d8c0:105a:9001::a154 | 2a06:c180:2::face | icmp6-echo | inconclusive | 2026-05-30T10:44:55Z |
| odin | 2607:fae0:a000::42 | 2a06:c180:2::face | icmp6-echo | honored | 2026-05-30T10:35:01Z |
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: timed outtls→ no_tcp: TLS connect failedhttp→ no_tcp: tcp/80 not open
Attempt log (odin):
icmp6-echo→ honored (size_before=1360, size_after=None): natural Echo Reply at 1400B was already split into IPv6 fragments without our PTB intervention -- the destination's stack has a cached path MTU below 1400B from a previously-honored ICMPv6 Type 2, which is itself evidence that this destination honors PTB on this path.dns-tcp→ no_tcp: connect failed: timed outtls→ 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): AS12778, AS174, AS50673.
- From go6lab (open/Type-2=honored) the path enters AS12778 at hop 14; from karsolink (open/Type-2=inconclusive) the same hop is in AS174. Last common AS: AS44549. 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: AS44549. The disagreement is most likely rooted in one of those two transit ASes.
- From karsolink (open/Type-2=inconclusive) the path enters AS44549 at hop 17; from odin (open/Type-2=honored) the same hop is in an opaque hop. Last common AS: AS44549. 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 | 2001:7f8:46:0:1:0:4:4549 | AS51988 | ARNES-SIX - ARNES, SI | ? no_response |
| 5 | 2a06:c180::10 | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI | ? no_response |
| 6 | 2a06:c180:2::face | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI | ? 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 | 1.4ms | 0% | AS203993 | STEFFANN-DC-AS - S.J.M. Steffann, NL |
| 2 | * | - | 0%* | - | |
| 3 | 2a00:1ca8:1::194 | 2.8ms | 0% | AS50673 | Serverius-as - Serverius Holding B.V., NL |
| 4 | 2a03:3f40::10:41 | 2.9ms | 0% | AS50673 | Serverius-as - Serverius Holding B.V., NL |
| 5 | * | - | 90% | - | |
| 6 | * | - | - | - | |
| 7 | be2950.ccr42.fra05.atlas.cogentco.com 2001:550:0:1000::9a36:482a | 12.2ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 8 | * | - | - | - | |
| 9 | be9456.ccr82.vie01.atlas.cogentco.com 2001:550:0:1000::9a36:3f8d | 23.4ms | 30% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 10 | be3935.agr61.vie01.atlas.cogentco.com 2001:550:0:1000::9a36:274e | 24.1ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 11 | be3189.rcr61.lju01.atlas.cogentco.com 2001:550:0:1000::9a36:4ac5 | 30.4ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 12 | be3191.nr61.b021176-0.lju01.atlas.cogentco.com 2001:550:0:1000::9a19:e7a | 30.5ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 13 | 2001:978:2:39::8:2 | 27.4ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 14 | 2a02:d68:2:9::1 | 27.9ms | 0% | AS12778 | SGN - MEGA M, d.o.o., SI |
| 15 | 2a02:d68:c:100e::2 | 28.9ms | 0% | AS12778 | SGN - MEGA M, d.o.o., SI |
| 16 | 2a06:c180::10 | 28.7ms | 0% | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI |
| 17 | 2a06:c180:2::face | 33.9ms | 0% | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI |
Rate-limited ICMPv6: hop 5, hop 9 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).
tracepath -6
1?: [LOCALHOST] 0.042ms pmtu 1500
1: 2a00:8642:42::3 1.795ms
1: 2a00:8642:42::3 1.346ms
2: gw.friends.steffann.nl 2.522ms
3: 2a00:1ca8:1::194 2.891ms
4: 2a03:3f40::10:41 3.723ms
5: no reply
6: no reply
7: be3343.ccr41.fra05.atlas.cogentco.com 11.619ms
8: no reply
9: be9456.ccr82.vie01.atlas.cogentco.com 23.593ms
10: be4079.agr61.vie01.atlas.cogentco.com 23.521ms
11: be9461.rcr62.lju01.atlas.cogentco.com 30.303ms
12: be3191.nr61.b021176-0.lju01.atlas.cogentco.com 30.054ms
13: 2001:978:2:39::8:2 28.177ms
14: 2a02:d68:2:9::1 27.750ms asymm 13
15: 2a02:d68:c:100e::2 27.813ms asymm 14
16: no reply
17: no reply
18: no reply
19: no reply
20: no reply
21: no reply
22: no reply
23: no reply
24: no reply
Too many hops: pmtu 1500
Resume: pmtu 1500 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 | * | - | - | - | |
| 2 | * | - | - | - | |
| 3 | * | - | - | - | |
| 4 | 2a03:b020:1:51::a | 10.3ms | 0% | AS41327 | FIBERTELECOM-AS - Fiber Telecom S.p.A., IT |
| 5 | 2a03:b020::246 | 10.1ms | 0% | AS41327 | FIBERTELECOM-AS - Fiber Telecom S.p.A., IT |
| 6 | 2001:978:2:2a::e7:1 | 11.0ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 7 | be4918.agr62.mil02.atlas.cogentco.com 2001:550:0:1000::9a19:8c9 | 11.0ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 8 | port-channel4689.ccr91.mil02.atlas.cogentco.com 2001:550:0:1000::9a36:3e92 | 10.3ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 9 | * | - | - | - | |
| 10 | be9456.ccr82.vie01.atlas.cogentco.com 2001:550:0:1000::9a36:3f8d | 26.9ms | 30% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 11 | be4080.agr62.vie01.atlas.cogentco.com 2001:550:0:1000::8275:3252 | 24.9ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 12 | be3189.rcr61.lju01.atlas.cogentco.com 2001:550:0:1000::9a36:4ac5 | 31.3ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 13 | be9462.nr61.b021176-0.lju01.atlas.cogentco.com 2001:550:0:1000::9a19:11a5 | 31.7ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 14 | 2001:978:2:39::8:2 | 60.3ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 15 | 2a02:d68:2:9::1 | 28.6ms | 0% | AS12778 | SGN - MEGA M, d.o.o., SI |
| 16 | 2a02:d68:c:100e::2 | 28.8ms | 0% | AS12778 | SGN - MEGA M, d.o.o., SI |
| 17 | 2a06:c180::10 | 32.6ms | 0% | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI |
| 18 | 2a06:c180:2::face | 49.6ms | 0% | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI |
Rate-limited ICMPv6: hop 10 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).
tracepath -6
1?: [LOCALHOST] 0.031ms pmtu 1500
1: no reply
2: 2a12:d8c0:109f:121::a1 1.056ms
3: 2a12:d8c0:101f:6::1 10.302ms
4: 2a03:b020:1:51::a 10.601ms
5: 2a03:b020::246 10.805ms asymm 6
6: 2001:978:2:2a::e7:1 11.357ms asymm 7
7: be4918.agr62.mil02.atlas.cogentco.com 11.047ms asymm 8
8: port-channel4689.ccr91.mil02.atlas.cogentco.com 10.751ms asymm 9
9: no reply
10: be5456.ccr81.vie01.atlas.cogentco.com 26.600ms asymm 11
11: be4080.agr62.vie01.atlas.cogentco.com 25.625ms asymm 12
12: be3189.rcr61.lju01.atlas.cogentco.com 31.673ms asymm 13
13: be3191.nr61.b021176-0.lju01.atlas.cogentco.com 31.973ms asymm 14
14: 2001:978:2:39::8:2 32.554ms asymm 9
15: 2a02:d68:2:9::1 29.243ms asymm 9
16: 2a02:d68:c:100e::2 29.333ms asymm 10
17: no reply
18: no reply
19: no reply
20: no reply
21: no reply
22: no reply
23: no reply
24: no reply
Too many hops: pmtu 1500
Resume: pmtu 1500 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 | 1.6ms | 0%* | AS8038 | 6CONNECT - 6connect, Inc., US |
| 2 | * | - | - | - | |
| 3 | 2a03:a100:0:201:1::1 | 7.5ms | - | AS56635 | XENYA - XENYA inzeniring, proizvodnja in trgovina, d.o.o. Ljubljana, SI |
| 4 | six2.mega-m.net @SIX 2001:7f8:46:0:1:0:4:4549 | 4.3ms | 0% | AS51988 | ARNES-SIX - ARNES, SI |
| 5 | 2a06:c180::10 | 2.4ms | 0% | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI |
| 6 | 2a06:c180:2::face | 15.5ms | 0% | AS44549 | MEGA-M-AS - MEGA M, d.o.o., SI |
tracepath -6
1?: [LOCALHOST] 0.023ms pmtu 1500
1: fw1-lju.6connect.com 0.426ms
1: fw1-lju.6connect.com 0.423ms
2: no reply
3: 2a03:a100:0:201:1::1 0.885ms
4: six2.mega-m.net 1.720ms
5: no reply
6: no reply
7: no reply
8: no reply
9: no reply
10: no reply
11: no reply
12: no reply
13: no reply
14: no reply
15: no reply
16: no reply
17: no reply
18: no reply
19: no reply
20: no reply
21: no reply
22: no reply
23: no reply
24: no reply
Too many hops: pmtu 1500
Resume: pmtu 1500