AS overview
Test target: 2a03:c380:4010:0:213:174:160:2 · ns3.acantho.net · address space: PA · prefixes announced: 1
prefix(es): 2a03:c380::/32
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 | ||
2a03:c380:4010:0:213:174:160:2ns3.acantho.net | NS | ✓ | ✓ | ? | ? | - | ✓ | ✓ | ? | ? | - | ✓ | ✓ | ? | ? | - |
MIX-IT / NAMEX / MINAP / TOP-IX / VSIX / EQUINIX-MILAN / BGPX-ROME / NAMEX-BARI / PCIX / DECIX-PALERMO peering
MIX-IT / NAMEX / MINAP / TOP-IX / VSIX / EQUINIX-MILAN / BGPX-ROME / NAMEX-BARI / PCIX / DECIX-PALERMO member - Open peering, peering member, since 2013-05-20. IPv6 LAN: 2001:7f8:b:100:1d1:a5d2:1309:84. Locations: -.
RPKI & ASPA
1 of 1 prefix(es) covered by a valid ROA.
| Prefix | RPKI state | Reason | Covering VRP(s) |
|---|---|---|---|
2a03:c380::/32 | ✓ valid | matched VRP (correct origin, length within maxLength) | AS21309 /32 maxLen 32 (ripe) |
Random-IP probe (yarrp) into the AS' prefixes
We probed 14 arbitrary IPv6 address(es) inside AS21309's announced prefix(es). No router inside the prefix responded. The deepest visible hop was 2a02:2d8:4:180f:232a::1 at hop 13 - that router answers ICMPv6 Echo. This is not in AS21309's announced prefix; operationally it's the AS-edge / peering interface (often on an IXP 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 to 1300-byte probe. (ICMPv6 Echo + forged PTB)
- SLO host (6connect): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
Why they disagree - reachability mismatch: One vantage couldn't drive a flow at all to this destination (no Echo Reply or no responding TCP port), so the active test had no behavioural change to observe. The other vantage's verdict is the only meaningful one here.
Failure detail — what to grep in your logs
| vantage | our source | your target | method | result | tested (UTC) |
|---|---|---|---|---|---|
| go6lab | 2a00:8642:42::75 | 2a03:c380:4010:0:213:174:160:2 | icmp6-echo | honored | 2026-05-30T12:44:59Z |
| karsolink | 2a12:d8c0:105a:9001::a154 | 2a03:c380:4010:0:213:174:160:2 | icmp6-echo | no_echo | 2026-05-30T12:52:40Z |
| odin | 2607:fae0:a000::42 | 2a03:c380:4010:0:213:174:160:2 | icmp6-echo | honored | 2026-05-30T12:44:44Z |
Attempt log (go6lab):
icmp6-echo→ honored (size_before=1460, size_after=None)dns-tcp→ inconclusive (size_before=156, size_after=None): max DNS-over-TCP segment 156B; not big enough to test PMTU shrinktls→ no_tcp: TLS connect failedhttp→ no_tcp: tcp/80 not open
Attempt log (karsolink):
icmp6-echo→ no_echo: no Echo Reply to 1300-byte probedns-tcp→ inconclusive (size_before=156, size_after=None): max DNS-over-TCP segment 156B; not big enough to test PMTU shrinktls→ 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→ inconclusive (size_before=156, size_after=None): max DNS-over-TCP segment 156B; not big enough to test PMTU shrinktls→ 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.
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 | 2.5ms | 0% | AS50673 | Serverius-as - Serverius Holding B.V., NL |
| 4 | 2a03:3f40::10:41 | 1.9ms | 0% | AS50673 | Serverius-as - Serverius Holding B.V., NL |
| 5 | * | - | 90% | - | |
| 6 | * | - | 80% | - | |
| 7 | be3343.ccr41.fra05.atlas.cogentco.com 2001:550:0:1000::9a36:3e8d | 11.9ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 8 | * | - | - | - | |
| 9 | port-channel5891.ccr91.mil02.atlas.cogentco.com 2001:550:0:1000::9a36:3db5 | 26.7ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 10 | be2155.rcr71.vce01.atlas.cogentco.com 2001:550:0:1000::9a36:2612 | 30.0ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 11 | be9705.rcr61.blq01.atlas.cogentco.com 2001:550:0:1000::9a36:38ba | 31.5ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 12 | 2001:978:2:51::2 | 30.2ms | 0% | AS174 | COGENT-174 - Cogent Communications, LLC, US |
| 13 | GW-AS21309.retn.net 2a02:2d8:4:180f:232a::1 | 33.6ms | 0% | AS9002 | RETN-AS - RETN Limited, GB |
| 14 | * | - | - | - | |
| 15 | * | - | - | - | |
| 16 | * | - | - | - | |
| 17 | * | - | - | - | |
| 18 | * | - | - | - | |
| 19 | * | - | 0% | - | |
| 20 | * | - | - | - | |
| 21 | * | - | - | - | |
| 22 | * | - | - | - | |
| 23 | * | - | - | - | |
| 24 | * | - | - | - |
Rate-limited ICMPv6: hop 5, hop 6 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).
tracepath -6
1?: [LOCALHOST] 0.045ms pmtu 1500
1: 2a00:8642:42::3 2.427ms
1: 2a00:8642:42::3 1.953ms
2: gw.friends.steffann.nl 3.225ms
3: 2a00:1ca8:1::194 3.250ms
4: 2a03:3f40::10:41 3.464ms
5: no reply
6: no reply
7: be3343.ccr41.fra05.atlas.cogentco.com 11.941ms
8: no reply
9: port-channel5892.ccr92.mil02.atlas.cogentco.com 25.686ms
10: be2434.rcr71.vce01.atlas.cogentco.com 30.301ms
11: be9705.rcr61.blq01.atlas.cogentco.com 31.417ms
12: 2001:978:2:51::2 29.930ms asymm 8
13: GW-AS21309.retn.net 34.506ms asymm 7
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 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 | * | - | 0%* | - | |
| 3 | * | - | 70% | - | |
| 4 | acantho-v6.mix-it.net @MIX-IT / NAMEX / MINAP / TOP-IX / VSIX / EQUINIX-MILAN / BGPX-ROME / NAMEX-BARI / PCIX / DECIX-PALERMO 2001:7f8:b:100:1d1:a5d2:1309:84 | 13.2ms | 0% | - | NA |
| 5 | * | - | - | - | |
| 6 | * | - | - | - | |
| 7 | * | - | - | - | |
| 8 | * | - | - | - | |
| 9 | * | - | - | - | |
| 10 | * | - | 0% | - | |
| 11 | * | - | - | - | |
| 12 | * | - | - | - | |
| 13 | * | - | - | - | |
| 14 | * | - | - | - | |
| 15 | * | - | - | - | |
| 16 | * | - | - | - | |
| 17 | * | - | - | - | |
| 18 | * | - | - | - | |
| 19 | * | - | - | - | |
| 20 | * | - | - | - | |
| 21 | * | - | - | - | |
| 22 | * | - | - | - | |
| 23 | * | - | - | - | |
| 24 | * | - | - | - |
Rate-limited ICMPv6: hop 3 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).
tracepath -6
1?: [LOCALHOST] 0.065ms pmtu 1500
1: karsolink-01.net.karsolink.com 0.977ms
2: 2a12:d8c0:109f:121::a1 0.964ms
3: 2a12:d8c0:101f:103::1 9.002ms
4: acantho-v6.mix-it.net 14.054ms
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 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 | * | - | - | - | |
| 4 | * | - | 90% | - | |
| 5 | * | - | - | - | |
| 6 | port-channel1.core1.zag2.he.net 2001:470:0:2ea::2 | 3.7ms | 60% | AS6939 | HURRICANE - Hurricane Electric LLC, US |
| 7 | * | - | - | - | |
| 8 | * | - | - | - | |
| 9 | * | - | - | - | |
| 10 | * | - | - | - | |
| 11 | * | - | - | - | |
| 12 | * | - | - | - | |
| 13 | * | - | - | - | |
| 14 | * | - | 0% | - | |
| 15 | * | - | - | - | |
| 16 | * | - | - | - | |
| 17 | * | - | - | - | |
| 18 | * | - | - | - | |
| 19 | * | - | - | - | |
| 20 | * | - | - | - | |
| 21 | * | - | - | - | |
| 22 | * | - | - | - | |
| 23 | * | - | - | - | |
| 24 | * | - | - | - |
Rate-limited ICMPv6: hop 4, hop 6 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).
tracepath -6
1?: [LOCALHOST] 0.051ms pmtu 1500
1: fw1-lju.6connect.com 1.248ms
1: fw1-lju.6connect.com 0.656ms
2: no reply
3: no reply
4: e0-1.core1.lju1.he.net 4.142ms
5: no reply
6: port-channel1.core1.zag2.he.net 5.288ms
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