AS2107 ARNES-NET - ARNES

AS overview

Test target: 2001:1470:8000::87 · aa.arnes.si · address space: mixed · prefixes announced: 2

prefix(es): 2001:1470::/29, 2001:1470::/32

Targets & per-vantage-point probe results (10 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)
Target IP / hostname	Source	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached
`2001:1470:8000:40::121` cdn.arnes.si	drv	✓	✓	open	open	-	✓	✓	open	open	-	✓	✓	open	open	-
`2001:1470:8000:40::134` ftp.arnes.si	drv	✓	✓	open	open	-	✓	✓	open	open	-	✓	✓	open	open	-
`2001:1470:8000:43::15:194` grafana.arnes.si	drv	✓	✓	?	?	-	✓	✓	?	?	-	✓	✓	?	?	-
`2001:1470:8000:43::24` git.arnes.si	drv	✓	✓	?	?	-	✓	✓	?	?	-	✓	✓	?	?	-
`2001:1470:8000:53::44` b.dns.si	NS	✓	✓	?	?	-	✓	✓	?	?	-	✓	✓	?	?	-
`2001:1470:8000::110` imap.arnes.si	drv	✓	✓	?	?	-	✓	✓	?	?	-	✓	✓	?	?	-
`2001:1470:8000::87` aa.arnes.si	NS	✓	✓	?	?	✓	✓	✓	?	?	✓	✓	✓	?	?	✓
`2001:1470:8000::89` dns2.arnes.si	drv	✓	✓	?	?	✓	✓	✓	?	?	✓	✓	✓	?	?	✓
`2001:1470:8000::90` dns1.arnes.si	drv	✓	✓	?	?	✓	✓	✓	?	?	✓	✓	✓	?	?	✓
`2001:1470:ff80::24` niobe.ijs.si	NS	✓	✓	?	?	-	✓	✓	refused	refused	-	✓	✓	refused	refused	-

SIX peering

SIX member - mandatory peering, peering member, since 1994-01-01. IPv6 LAN: 2001:7f8:46:0:1::2107. Locations: lj_ijs, lj_tpl.

rs1-lan1-ipv6 → 2001:7f8:46:0:1::2107 Established (loc: lj_tpl, since 2026-05-28)
rs1-lan1-ipv6 → 2001:7f8:46::2107 Established (loc: lj_ijs, since 2026-05-23)
rs2-lan1-ipv6 → 2001:7f8:46:0:1::2107 Established (loc: lj_tpl, since 2026-05-12)
rs2-lan1-ipv6 → 2001:7f8:46::2107 Established (loc: lj_ijs, since 2026-05-12)

Announces via SIX route servers: 13 prefix(es) - 2001:1470::/29, 2001:1470::/32, 2001:503:231d::/48, 2001:503:c27::/48, 2001:678:4::/48, 2001:678:5::/48, 2400:cb00:1254::/48, 2620:7d:e000::/48 (+5 more)

RPKI & ASPA

2 of 2 prefix(es) covered by a valid ROA.

Prefix	RPKI state	Reason	Covering VRP(s)
`2001:1470::/29`	✓ valid	matched VRP (correct origin, length within maxLength)	AS2107 /29 maxLen 32 (ripe)
`2001:1470::/32`	✓ valid	matched VRP (correct origin, length within maxLength)	AS2107 /29 maxLen 32 (ripe)

Random-IP probe (yarrp) into the AS' prefixes

At least one router inside AS2107's announced prefix replied during the random-target probe. Hop(s): 2001:1470:a:74::b. 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 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`	`2001:1470:8000::87`	`icmp6-echo`	honored	2026-05-30T10:30:26Z
karsolink	`2a12:d8c0:105a:9001::a154`	`2001:1470:8000::87`	`icmp6-echo`	no_echo	2026-05-30T10:30:45Z
odin	`2607:fae0:a000::42`	`2001:1470:8000::87`	`icmp6-echo`	honored	2026-05-30T10:30:24Z

Attempt log (go6lab):

icmp6-echo → honored (size_before=1460, size_after=None)
dns-tcp → no_tcp: no DNS response data
tls → no_tcp: TLS connect failed
http → no_tcp: tcp/80 not open

Attempt log (karsolink):

icmp6-echo → no_echo: no Echo Reply to 1300-byte probe
dns-tcp → inconclusive (size_before=156, size_after=None): max DNS-over-TCP segment 156B; not big enough to test PMTU shrink
tls → no_tcp: TLS connect failed
http → no_tcp: tcp/80 not open

Attempt log (odin):

icmp6-echo → honored (size_before=1460, size_after=None)
dns-tcp → inconclusive (size_before=56, size_after=None): max DNS-over-TCP segment 56B; not big enough to test PMTU shrink
tls → no_tcp: TLS connect failed
http → 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 → verdict honored
karsolink: probe icmp6-echo → verdict no_echo
odin: probe icmp6-echo → verdict honored

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	no_echo	inconclusive	no_tcp	no_tcp
odin	honored	inconclusive	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): AS174, AS50673, AS56635.

From go6lab (open/Type-2=honored) the path enters an opaque hop at hop 13; from karsolink (open/Type-2=no_echo) the same hop is in AS174. Last common AS: AS2107. 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: AS2107. The disagreement is most likely rooted in one of those two transit ASes.
From karsolink (open/Type-2=no_echo) the path enters AS2107 at hop 15; from odin (open/Type-2=honored) the same hop is in an opaque hop. Last common AS: AS2107. 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

An operator-targeted diagnostic interpretation can be generated for this AS on demand. The pipeline holds the raw verdicts and the per-hop walk; an AI pass synthesises where to start looking. Click the button below to run it.

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	2607:fae0:a000:2::2	AS8038	6CONNECT - 6connect, Inc., US	- skipped (CoPP)
3	2a03:a100:0:201:1::1	AS56635	XENYA - XENYA inzeniring, proizvodnja in	✓ honored
4	2001:7f8:46::2107	AS2107	Arnes	? no_response
5	2001:1470:a:75::b	AS2107	ARNES-NET - ARNES, SI	? no_response
6	2001:1470:8000:712::2	AS2107	ARNES-NET - ARNES, SI	? no_response
7	2001:1470:8000:300::4	AS2107	ARNES-NET - ARNES, SI	? no_response
8	2001:1470:8000::87	AS2107	ARNES-NET - ARNES, 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.

tracepath6 per-hop PMTU drilldown

For each target where Type 2 verdicts disagreed across vantages, tracepath -6 ran from every vantage to capture per-hop PMTU evolution along that vantage's actual forward path. A pmtu change entry on a hop means that hop's router generated a PTB and we observed the shrink; absence of any change combined with a not_honored verdict suggests a router somewhere downstream is silently dropping >MTU packets (an RFC 4890 violation) rather than sending a PTB.

Target `2001:1470:8000:40::121`

go6lab — verdict honored

verdict = honored; final pmtu = 1500

#	hop IP	pmtu change
1	<span class='muted'>no reply</span>
2	2a00:8642:1000:f000::1
3	2a00:1ca8:1::194
4	2a03:3f40::10:41
5	<span class='muted'>no reply</span>
6	<span class='muted'>no reply</span>
7	2001:550:0:1000::9a36:482a
8	<span class='muted'>no reply</span>
9	2001:550:0:1000::9a36:3f8d
10	2001:550:0:1000::8275:3242
11	2001:550:0:1000::9a36:48a2
12	2001:550:0:1000::9a19:11a5
13	<span class='muted'>no reply</span>
14	2001:1470:a:74::b
15	2001:1470:10dc:1021::1
16	2001:1470:10dc:1023::1
17	<span class='muted'>no reply</span>
18	<span class='muted'>no reply</span>
19	<span class='muted'>no reply</span>
20	<span class='muted'>no reply</span>
21	<span class='muted'>no reply</span>
22	<span class='muted'>no reply</span>
23	<span class='muted'>no reply</span>
24	<span class='muted'>no reply</span>

karsolink — verdict not_honored

verdict = not_honored; final pmtu = 1500

#	hop IP	pmtu change
1	<span class='muted'>no reply</span>
2	2a12:d8c0:109f:121::a1
3	2a12:d8c0:101f:6::1
4	2a03:b020:1:51::a
5	2a03:b020::246
6	2001:978:2:2a::e7:1
7	2001:550:0:1000::9a19:8c9
8	2001:550:0:1000::9a36:4d39
9	<span class='muted'>no reply</span>
10	2001:550:0:1000::9a36:48a6
11	2001:550:0:1000::8275:3252
12	2001:550:0:1000::9a36:4ac5
13	2001:550:0:1000::9a19:e7a
14	<span class='muted'>no reply</span>
15	2001:1470:a:74::b
16	2001:1470:10dc:1021::1
17	2001:1470:10dc:1023::1
18	<span class='muted'>no reply</span>
19	<span class='muted'>no reply</span>
20	<span class='muted'>no reply</span>
21	<span class='muted'>no reply</span>
22	<span class='muted'>no reply</span>
23	<span class='muted'>no reply</span>
24	<span class='muted'>no reply</span>

odin — verdict honored

verdict = honored; final pmtu = 1500

#	hop IP	pmtu change
1	<span class='muted'>no reply</span>
2	2607:fae0:a000:2::2
3	2a03:a100:0:201:1::1
4	2001:7f8:46::2107
5	2001:1470:a:75::b
6	2001:1470:a:7b::1
7	2001:1470:10dc:1021::1
8	2001:1470:10dc:1023::1
9	<span class='muted'>no reply</span>
10	<span class='muted'>no reply</span>
11	<span class='muted'>no reply</span>
12	<span class='muted'>no reply</span>
13	<span class='muted'>no reply</span>
14	<span class='muted'>no reply</span>
15	<span class='muted'>no reply</span>
16	<span class='muted'>no reply</span>
17	<span class='muted'>no reply</span>
18	<span class='muted'>no reply</span>
19	<span class='muted'>no reply</span>
20	<span class='muted'>no reply</span>
21	<span class='muted'>no reply</span>
22	<span class='muted'>no reply</span>
23	<span class='muted'>no reply</span>
24	<span class='muted'>no reply</span>

Target `2001:1470:8000:40::134`

go6lab — verdict honored

verdict = honored; final pmtu = 1500

#	hop IP	pmtu change
1	<span class='muted'>no reply</span>
2	2a00:8642:1000:f000::1
3	2a00:1ca8:1::194
4	2a03:3f40::10:41
5	<span class='muted'>no reply</span>
6	<span class='muted'>no reply</span>
7	2001:550:0:1000::9a36:482a
8	<span class='muted'>no reply</span>
9	2001:550:0:1000::9a36:48a6
10	2001:550:0:1000::9a36:274e
11	2001:550:0:1000::9a36:48a2
12	2001:550:0:1000::9a19:11a5
13	<span class='muted'>no reply</span>
14	2001:1470:a:74::b
15	2001:1470:10dc:1021::1
16	2001:1470:10dc:1023::1
17	<span class='muted'>no reply</span>
18	<span class='muted'>no reply</span>
19	<span class='muted'>no reply</span>
20	<span class='muted'>no reply</span>
21	<span class='muted'>no reply</span>
22	<span class='muted'>no reply</span>
23	<span class='muted'>no reply</span>
24	<span class='muted'>no reply</span>

karsolink — verdict not_honored

verdict = not_honored; final pmtu = 1500

#	hop IP	pmtu change
1	<span class='muted'>no reply</span>
2	2a12:d8c0:109f:121::a1
3	2a12:d8c0:101f:6::1
4	2a03:b020:1:51::a
5	2a03:b020::246
6	2001:978:2:2a::e7:1
7	2001:550:0:1000::9a19:8c5
8	2001:550:0:1000::9a36:3f3e
9	<span class='muted'>no reply</span>
10	2001:550:0:1000::9a36:48a6
11	2001:550:0:1000::9a36:276e
12	2001:550:0:1000::9a36:48a2
13	2001:550:0:1000::9a19:e7a
14	<span class='muted'>no reply</span>
15	2001:1470:a:74::b
16	2001:1470:10dc:1021::1
17	2001:1470:10dc:1023::1
18	<span class='muted'>no reply</span>
19	<span class='muted'>no reply</span>
20	<span class='muted'>no reply</span>
21	<span class='muted'>no reply</span>
22	<span class='muted'>no reply</span>
23	<span class='muted'>no reply</span>
24	<span class='muted'>no reply</span>

odin — verdict honored

verdict = honored; final pmtu = 1500

#	hop IP	pmtu change
1	<span class='muted'>no reply</span>
2	2607:fae0:a000:2::2
3	2a03:a100:0:201:1::1
4	2001:7f8:46::2107
5	2001:1470:a:75::b
6	2001:1470:a:7b::1
7	2001:1470:10dc:1021::1
8	2001:1470:10dc:1023::1
9	<span class='muted'>no reply</span>
10	<span class='muted'>no reply</span>
11	<span class='muted'>no reply</span>
12	<span class='muted'>no reply</span>
13	<span class='muted'>no reply</span>
14	<span class='muted'>no reply</span>
15	<span class='muted'>no reply</span>
16	<span class='muted'>no reply</span>
17	<span class='muted'>no reply</span>
18	<span class='muted'>no reply</span>
19	<span class='muted'>no reply</span>
20	<span class='muted'>no reply</span>
21	<span class='muted'>no reply</span>
22	<span class='muted'>no reply</span>
23	<span class='muted'>no reply</span>
24	<span class='muted'>no reply</span>

From NL host (go6lab) openRFC 4890 ✓

filter likely at: (none) · min PMTU on path: 1500

4/4

Echo small (56B) 28.7ms

3/4

Echo 1500B (DF) 28.9ms

yes

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	2a00:8642:42::3	1.5ms	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	2a00:1ca8:1::194	2.8ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
4	2a03:3f40::10:41	2.7ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
5	*	-	90%	-
6	*	-	60%	-
7	be3343.ccr41.fra05.atlas.cogentco.com 2001:550:0:1000::9a36:3e8d	11.6ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
8	*	-	30%	-
9	be9456.ccr82.vie01.atlas.cogentco.com 2001:550:0:1000::9a36:3f8d	23.2ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
10	be4080.agr62.vie01.atlas.cogentco.com 2001:550:0:1000::8275:3252	22.8ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
11	be3189.rcr61.lju01.atlas.cogentco.com 2001:550:0:1000::9a36:4ac5	29.5ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
12	be3191.nr61.b021176-0.lju01.atlas.cogentco.com 2001:550:0:1000::9a19:e7a	29.4ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
13	*	-	-	-
14	rljtpl1.bb.arnes.si 2001:1470:a:74::b	30.9ms	0%	AS2107	ARNES-NET - ARNES, SI
15	2001:1470:8000:713::2	30.0ms	0%	AS2107	ARNES-NET - ARNES, SI
16	kosuta-v6.arnes.si 2001:1470:8000:300::4	29.3ms	0%	AS2107	ARNES-NET - ARNES, SI
17	kanin.arnes.si 2001:1470:8000::87	29.4ms	0%	AS2107	ARNES-NET - ARNES, SI

Rate-limited ICMPv6: hop 5, hop 6, hop 8 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.069ms pmtu 1500
 1:  2a00:8642:42::3                                       1.934ms 
 1:  2a00:8642:42::3                                       1.291ms 
 2:  no reply
 3:  2a00:1ca8:1::194                                      3.525ms 
 4:  2a03:3f40::10:41                                      2.195ms 
 5:  no reply
 6:  no reply
 7:  be2950.ccr42.fra05.atlas.cogentco.com                13.072ms 
 8:  no reply
 9:  be9456.ccr82.vie01.atlas.cogentco.com                29.258ms 
10:  be7244.agr62.vie01.atlas.cogentco.com                24.091ms 
11:  be3189.rcr61.lju01.atlas.cogentco.com                31.958ms 
12:  be3191.nr61.b021176-0.lju01.atlas.cogentco.com       31.233ms 
13:  no reply
14:  rljtpl1.bb.arnes.si                                  29.977ms 
15:  2001:1470:8000:713::2                                29.937ms 
16:  2001:1470:8000:713::2                                32.505ms !H
     Resume: pmtu 1500

From ITA host (Karsolink) open

filter likely at: (none) · min PMTU on path: 1500

4/4

Echo small (56B) 31.0ms

4/4

Echo 1500B (DF) 30.9ms

yes

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	*	-	-	-
2	*	-	-	-
3	*	-	60%	-
4	2a03:b020:1:51::a	10.3ms	0%	AS41327	FIBERTELECOM-AS - Fiber Telecom S.p.A., IT
5	2a03:b020::246	10.3ms	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	10.6ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
8	port-channel4690.ccr92.mil02.atlas.cogentco.com 2001:550:0:1000::9a36:3f3e	10.2ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
9	*	-	60%	-
10	be5456.ccr81.vie01.atlas.cogentco.com 2001:550:0:1000::9a36:48a6	25.1ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
11	be7244.agr62.vie01.atlas.cogentco.com 2001:550:0:1000::9a36:276e	25.0ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
12	be9461.rcr62.lju01.atlas.cogentco.com 2001:550:0:1000::9a36:48a2	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	*	-	-	-
15	rljtpl1.bb.arnes.si 2001:1470:a:74::b	33.8ms	0%	AS2107	ARNES-NET - ARNES, SI
16	2001:1470:8000:713::2	33.9ms	0%	AS2107	ARNES-NET - ARNES, SI
17	kosuta-v6.arnes.si 2001:1470:8000:300::4	34.1ms	0%	AS2107	ARNES-NET - ARNES, SI
18	kanin.arnes.si 2001:1470:8000::87	34.4ms	0%	AS2107	ARNES-NET - ARNES, SI

Rate-limited ICMPv6: hop 3, hop 9 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.028ms pmtu 1500
 1:  no reply
 2:  2a12:d8c0:109f:121::a1                                0.829ms 
 3:  2a12:d8c0:101f:6::1                                  10.541ms 
 4:  2a03:b020:1:51::a                                    10.627ms 
 5:  2a03:b020::246                                       10.727ms asymm  6 
 6:  2001:978:2:2a::e7:1                                  11.283ms asymm  7 
 7:  be4823.agr61.mil02.atlas.cogentco.com                11.361ms asymm  8 
 8:  port-channel3333.ccr91.mil02.atlas.cogentco.com      10.943ms asymm  9 
 9:  no reply
10:  be5456.ccr81.vie01.atlas.cogentco.com                26.385ms asymm 11 
11:  be7244.agr62.vie01.atlas.cogentco.com                25.598ms asymm 12 
12:  be9461.rcr62.lju01.atlas.cogentco.com                31.642ms asymm 13 
13:  be9462.nr61.b021176-0.lju01.atlas.cogentco.com       32.400ms asymm 14 
14:  no reply
15:  rljtpl1.bb.arnes.si                                  34.070ms asymm 13 
16:  2001:1470:8000:713::2                                34.560ms asymm 11 
17:  2001:1470:8000:713::2                                34.513ms !H
     Resume: pmtu 1500

From SLO host (6connect) openRFC 4890 ✓

filter likely at: (none) · min PMTU on path: 1500

4/4

Echo small (56B) 1.4ms

4/4

Echo 1500B (DF) 3.4ms

yes

Type 1 dest-unreach

TCP responds on

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	ccr-to-fw-ccr1-gw-lju.6connect.com 2607:fae0:a000:2::2	0.5ms	-	AS8038	6CONNECT - 6connect, Inc., US
3	2a03:a100:0:201:1::1	1.2ms	60%	AS56635	XENYA - XENYA inzeniring, proizvodnja in trgovina, d.o.o. Ljubljana, SI
4	rarnes1.six.si @SIX 2001:7f8:46::2107	8.1ms	0%	AS2107	Arnes
5	rljijs1.bb.arnes.si 2001:1470:a:75::b	0.9ms	0%	AS2107	ARNES-NET - ARNES, SI
6	2001:1470:8000:712::2	1.6ms	0%	AS2107	ARNES-NET - ARNES, SI
7	kosuta-v6.arnes.si 2001:1470:8000:300::4	2.6ms	0%	AS2107	ARNES-NET - ARNES, SI
8	kanin.arnes.si 2001:1470:8000::87	3.1ms	0%	AS2107	ARNES-NET - ARNES, SI

Rate-limited ICMPv6: hop 3 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.043ms pmtu 1500
 1:  fw1-lju.6connect.com                                  1.219ms 
 1:  fw1-lju.6connect.com                                  0.683ms 
 2:  ccr-to-fw-ccr1-gw-lju.6connect.com                    1.052ms 
 3:  2a03:a100:0:201:1::1                                  1.309ms 
 4:  rarnes1.six.si                                        5.024ms 
 5:  rljijs1.bb.arnes.si                                   1.336ms 
 6:  2001:1470:8000:712::2                                 1.189ms 
 7:  2001:1470:8000:712::2                                 1.380ms !H
     Resume: pmtu 1500

AS overview

SIX peering

RPKI & ASPA

Random-IP probe (yarrp) into the AS' prefixes

ICMPv6 Type 2 (Packet Too Big) acceptance - active test

Where the path divergence is

✨ Diagnostic interpretation

Per-hop PTB acceptance walk

tracepath6 per-hop PMTU drilldown

Target 2001:1470:8000:40::121

Target 2001:1470:8000:40::134

From NL host (go6lab) openRFC 4890 ✓

Path (traceroute + mtr + PTR)

tracepath -6

From ITA host (Karsolink) open

Path (traceroute + mtr + PTR)

tracepath -6

From SLO host (6connect) openRFC 4890 ✓

Path (traceroute + mtr + PTR)

tracepath -6

Target `2001:1470:8000:40::121`

Target `2001:1470:8000:40::134`