AS39729 REGISTER-AS REGISTER S.P.A.

AS overview

Test target: 2a01:8100:2911::2:184:2 · ns1.register.it · address space: PA · prefixes announced: 1

prefix(es): 2a01:8100:2000::/36

Targets & per-vantage-point probe results (1 target(s) across 7 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	SRB host (SOX, Belgrade)					DE host (Berlin)					DE host (Düsseldorf)					NL host (go6lab)					ITA host (Karsolink)					SLO host (6connect)					SLO host (T-2)
Target IP / hostname	Source	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached
`2a01:8100:2911::2:184:2` ns1.register.it	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 2017-01-17. IPv6 LAN: 2001:7f8:b:100:1d1:a5d2:9550:113. Locations: -.

RPKI & ASPA

1 of 1 prefix(es) covered by a valid ROA.

Prefix	RPKI state	Reason	Covering VRP(s)
`2a01:8100:2000::/36`	✓ valid	matched VRP (correct origin, length within maxLength)	AS39729 /36 maxLen 48 (ripe); AS39729 /29 maxLen 48 (ripe)

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

We probed 35 arbitrary IPv6 address(es) inside AS39729's announced prefix(es). No router inside the prefix responded. The deepest visible hop was 2001:4ba0:ffe9:db::2 at hop 11 - that router answers ICMPv6 Echo. This is not in AS39729'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

Type 2 not honored. Forged ICMPv6 PTB (MTU=1280) had no effect: the next 1500-byte Echo Reply still arrived whole (1460 B, no Fragment Header). PMTUD does not work toward this address from us.
method: ICMPv6 Echo + forged PTB, tested 2026-09-23T12:01:47Z

Failure detail - what to grep in your logs

vantage	our source	your target	method	result	tested (UTC)
belgrade	`2a09:ab81::91`	`2a01:8100:2911::2:184:2`	`icmp6-echo`	not_honored	2026-09-23T12:01:47Z
berlin	`2a06:d1c1:10b::cccc`	`2a01:8100:2911::2:184:2`	`icmp6-echo`	not_honored	2026-09-23T12:01:46Z
duseldorf	`2a06:d1c1:10d::aaaa`	`2a01:8100:2911::2:184:2`	`icmp6-echo`	not_honored	2026-09-23T12:01:46Z
go6lab	`2a00:8642:42::75`	`2a01:8100:2911::2:184:2`	`icmp6-echo`	not_honored	2026-09-23T12:02:32Z
karsolink	`2a12:d8c0:105a:9001::a154`	`2a01:8100:2911::2:184:2`	`icmp6-echo`	not_honored	2026-09-23T12:01:47Z
odin	`2607:fae0:a000::42`	`2a01:8100:2911::2:184:2`	`icmp6-echo`	not_honored	2026-09-23T12:01:45Z
t2	`2a01:261:313:b814:2a0:98ff:fe5b:13e4`	`2a01:8100:2911::2:184:2`	`icmp6-echo`	not_honored	2026-09-23T12:01:47Z

Attempt log (belgrade):

icmp6-echo → not_honored (reply shrank 1460→1460 B)
dns-tcp → inconclusive (reply 119 B before PTB): max DNS-over-TCP segment 119B; not big enough to test PMTU shrink
tls → no_tcp: TLS connect failed
http → no_tcp: tcp/80 not open

Attempt log (berlin):

icmp6-echo → not_honored (reply shrank 1460→1460 B)
dns-tcp → inconclusive (reply 156 B before PTB): 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 (duseldorf):

icmp6-echo → not_honored (reply shrank 1460→1460 B)
dns-tcp → inconclusive (reply 156 B before PTB): 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 (go6lab):

icmp6-echo → not_honored (reply shrank 1460→1460 B)
dns-tcp → inconclusive (reply 156 B before PTB): 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 (karsolink):

icmp6-echo → not_honored (reply shrank 1460→1460 B)
dns-tcp → inconclusive (reply 156 B before PTB): 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 → not_honored (reply shrank 1460→1460 B)
dns-tcp → inconclusive (reply 156 B before PTB): 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 (t2):

icmp6-echo → not_honored (reply shrank 1460→1460 B)
dns-tcp → inconclusive (reply 156 B before PTB): 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

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 2a01:261:313:b814:2a0:98ff:fe5b:13e4 or src host 2a06:d1c1:10b::cccc or src host 2a06:d1c1:10d::aaaa or src host 2a09:ab81::91 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 some of our source IPs but not others, the drop is path-asymmetric - at least one transit on the differing route is filtering.

What does "Type 2 not honored" actually mean? - click to expand

What this test does

Using the icmp6-echo method, we send a 1500-byte ICMPv6 Echo Request, then a forged ICMPv6 Type 2 (Packet Too Big) declaring path MTU=1280, and observe whether the next Echo Reply arrives split into IPv6 fragments. RFC 4890 requires hosts and intermediate networks not to filter ICMPv6 Type 2; the destination's TCP/UDP stack must act on a received PTB by lowering its Path MTU cache for that destination, which makes subsequent segments smaller.

What we measured

The TCP segment size your server emitted before our forged Type 2 was 1460 B; after, it was 1460 B. No change. RFC 4890 ("Type 2 messages MUST NOT be filtered") expects subsequent segments to shrink to fit a Path MTU of 1280 B.

Three plausible causes

Your host firewall is dropping ICMPv6 Type 2 inbound. Many default firewall rule sets only allow Echo Request/Reply and Neighbor Discovery, silently dropping all other ICMPv6 types - including Packet Too Big.
An upstream / transit network is dropping ICMPv6 Type 2 before it reaches you. Some transit ASes filter ICMPv6 messages other than Echo at the edge. The forged PTB never arrives, so your stack never has a chance to act on it.
Your kernel is ignoring the PTB. Linux / BSD stacks normally accept ICMPv6 PTB and update the route cache, but a few sysctls (or a hardened kernel) can be configured to ignore PMTU updates - typically as part of an over-aggressive anti-spoofing or uRPF policy.

How to check & fix (Linux examples)

1. Confirm Type 2 is not blocked at the host firewall:

sudo ip6tables -L INPUT -nv | grep -iE 'icmpv6|packet-too-big'
sudo nft list ruleset 2>/dev/null | grep -A1 'icmpv6'

If you see rules dropping ICMPv6 unconditionally, change them to permit at least icmpv6 type packet-too-big (and destination-unreachable, time-exceeded, parameter-problem per RFC 4890).

2. Confirm the kernel accepts incoming PTB:

sudo sysctl net.ipv6.conf.all.accept_redirects net.ipv4.ip_no_pmtu_disc net.ipv6.route.mtu_expires

The defaults (accept_redirects=1, ip_no_pmtu_disc=0) are the right values for honoring PTB.

3. Live trace: while we have an open TCP flow with a small MSS (we run our test from 2607:fae0:a000::42 on odin, 2a00:8642:42::75 on go6lab, 2a12:d8c0:105a:9001::a154 on karsolink, 2a09:ab81::91 on belgrade, 2a01:261:313:b814:2a0:98ff:fe5b:13e4 on t2, 2a06:d1c1:10a::bbbb on amsterdam, 2a06:d1c1:10d::aaaa on duseldorf and 2a06:d1c1:10b::cccc on berlin), watch for our forged Type 2 arriving on your interface:

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 or src host 2a09:ab81::91 or src host 2a01:261:313:b814:2a0:98ff:fe5b:13e4 or src host 2a06:d1c1:10a::bbbb or src host 2a06:d1c1:10d::aaaa or src host 2a06:d1c1:10b::cccc)'

If you see our PTBs arriving but TCP segments still stay big, the drop is in your kernel or NIC offload (cause 3). If you don't see them at all, the drop is upstream of you (cause 2) - ask your upstream(s) to permit ICMPv6 Type 2.

4. If your test target above (2026-09-23T12:01:47Z) is a host that you don't own (e.g. a third-party DNS / TLS server you happen to operate prefixes for), the verdict reflects that specific host's behaviour - try the test against a server you do own and we'll happily re-run.

RFC 4890 references: §4.3.1 (Packet Too Big - MUST NOT be dropped), and RFC 8201 for the broader PMTUD requirement.

Multi-vantage path map

Every hop of all vantages’ traceroutes toward the target, drawn left→right, grouped into per-AS bubbles (a hop seen from several vantages is one shared bubble, so converging paths merge). It answers two questions per vantage — shown on each source bubble as echo ✓/⚠/✗ · trace ✓/✗: did the destination reply to ICMPv6 Echo (✓ honored, ⚠ replied but PTB not honored, ✗ no reply), and did the traceroute reach it. A line to the target is drawn only when that vantage got an echo reply — solid if the PTB was honored, dashed if not (reachable but a broken-PMTUD / RFC 4890 violation). The path depth still shows how far the traceroute itself got, and runs of unanswered (* *) hops collapse into one dashed “silent” bubble. Open full size ↗

● SRB host (SOX, Belgrade)
● DE host (Berlin)
● DE host (Düsseldorf)
● NL host (go6lab)
● ITA host (Karsolink)
● SLO host (6connect)
● SLO host (T-2)
── solid line = echo reply, PTB honored (clean reach)
— — dashed line = echo reply but PTB not honored (RFC 4890 violation)
no line = no echo reply (never reached)
◉ target: green = clean, amber = reachable-but-violation / unreachable
⚠ suspected drop AS
⋯ silent (unanswered) hops
● IXP hop

From SRB host (SOX, Belgrade) openRFC 4890 ✗

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

4/4

Echo small (56B) 44.5ms

4/4

Echo 1500B (DF) 44.5ms

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	2a09:ab81::1	0.2ms	0%*	AS60733	PERKE-NET - ZORAN PEROVIC trading as Agencija Perke.NET, RS
2	sox-pn.sox.rs 2001:7f8:1e:8::3a	0.2ms	0%	AS13004	SOX - Serbian Open Exchange DOO, RS
3	2001:7f8:1e:8::3d	0.3ms	0%	AS13004	SOX - Serbian Open Exchange DOO, RS
4	*	-	0%	-
5	*	-	0%	-
6	*	-	-	-
7	*	-	-	-
8	*	-	-	-
9	*	-	-	-
10	*	-	-	-
11	*	-	-	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-

tracepath -6

 1?: [LOCALHOST]                        0.021ms pmtu 1500
 1:  _gateway                                              0.833ms 
 1:  _gateway                                              1.000ms 
 2:  sox-pn.sox.rs                                         0.427ms 
 3:  2001:7f8:1e:8::3d                                     0.546ms asymm  2 
 4:  2001:67c:128c::699                                   17.869ms 
 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
     Too many hops: pmtu 1500
     Resume: pmtu 1500

From DE host (Berlin) openRFC 4890 ✗

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

4/4

Echo small (56B) 19.0ms

4/4

Echo 1500B (DF) 19.1ms

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	*	-	0%*	-
2	ae0-2453.cr10.ber01.lwlcom.net 2a06:d1c0::dead:beef:1c02	0.7ms	0%*	AS59645	WYBT-NET - Tobias Fiebig, DE
3	ae0-150.cr10.fra01.lwlcom.net 2a00:c380:b200:230::174	10.3ms	0%	AS50629	LWLCOM - LWLcom GmbH, DE
4	ae6-3257.cr5-fra2.ip6.gtt.net 2001:668:0:3:ffff:1:0:3d5d	9.5ms	0%	AS3257	GTT-BACKBONE - GTT Communications Inc., US
5	2001:668:0:2:ffff:0:5995:8d0a	17.7ms	0%	AS3257	GTT-BACKBONE - GTT Communications Inc., US
6	cotendo-gw.ip6.gtt.net 2001:668:0:3::a000:222	18.8ms	0%	AS3257	GTT-BACKBONE - GTT Communications Inc., US
7	2a01:8100:2000:6000::19	19.1ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
8	2a01:8100:2000:6000::22	27.2ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
9	*	-	0%	-
10	*	-	-	-
11	*	-	-	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-

tracepath -6

 1?: [LOCALHOST]                        0.029ms pmtu 1500
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.430ms 
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.441ms 
 2:  ae0-2453.cr10.ber01.lwlcom.net                        0.975ms 
 3:  ae0-150.cr10.fra01.lwlcom.net                        10.542ms asymm  7 
 4:  ae6-3257.cr5-fra2.ip6.gtt.net                         9.756ms asymm  9 
 5:  2001:668:0:2:ffff:0:5995:8d0a                        17.996ms asymm  9 
 6:  cotendo-gw.ip6.gtt.net                               19.111ms asymm 11 
 7:  2a01:8100:2000:6000::19                              19.693ms asymm 12 
 8:  2a01:8100:2000:6000::22                              19.224ms asymm 13 
 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
     Too many hops: pmtu 1500
     Resume: pmtu 1500

From DE host (Düsseldorf) openRFC 4890 ✗

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

4/4

Echo small (56B) 20.4ms

4/4

Echo 1500B (DF) 20.4ms

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	*	-	0%*	-
2	eth1-0-12-h5594.edge5-dus1.bb.wiit.network 2001:4ba0:92f4:3::1	20.0ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
3	lag10-h5f01.agr4-dus1.bb.wiit.network 2001:4ba0:ffe9:7c::1	157.3ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
4	lag11.core3-dus1.bb.wiit.network 2001:4ba0:ffe9:115::3	0.2ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
5	lag0-vl1011.core1-fra-ix.bb.wiit.network 2001:4ba0:ffe9:8a::2	4.1ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
6	lag0-vl1001.core1-nbg-ncd.bb.wiit.network 2001:4ba0:ffe9:103e::1	6.9ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
7	lag0-vl6.core2-nbg-ncd.bb.wiit.network 2001:4ba0:ffe9:103b::1	7.1ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
8	2001:4ba0:ffe9:b8	9.7ms	0%	-
9	lag0-vl1009.core1-muc-eq3.bb.wiit.network 2001:4ba0:ffe9:a7::1	9.7ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
10	lag0-vl1001.core1-pda-vsix.bb.wiit.network 2001:4ba0:ffe9:da::2	20.1ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
11	lag0-vl1001.core1-mil-mix.bb.wiit.network 2001:4ba0:ffe9:db::2	20.3ms	0%	AS24961	MYLOC-AS - WIIT AG, DE
12	dada-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:a5d2:9550:113	21.6ms	0%	-	NA
13	2a01:8100:2000:6000::19	20.4ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
14	2a01:8100:2000:6000::22	20.4ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
15	*	-	0%	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-

tracepath -6

 1?: [LOCALHOST]                        0.014ms pmtu 1500
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.500ms 
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.275ms 
 2:  eth1-0-12-h5594.edge5-dus1.bb.wiit.network           16.347ms 
 3:  no reply
 4:  lag30.core3-dus1.bb.wiit.network                      0.252ms 
 5:  lag0-vl1011.core1-fra-ix.bb.wiit.network              4.293ms 
 6:  lag0-vl1001.core1-nbg-ncd.bb.wiit.network             6.821ms 
 7:  lag0-vl6.core2-nbg-ncd.bb.wiit.network                6.742ms 
 8:  lag0-vl1006.core2-muc2.bb.wiit.network                9.426ms 
 9:  lag0-vl1009.core1-muc-eq3.bb.wiit.network             9.621ms 
10:  lag0-vl1001.core1-pda-vsix.bb.wiit.network           20.369ms 
11:  lag0-vl1001.core1-mil-mix.bb.wiit.network            20.061ms asymm  9 
12:  dada-v6.mix-it.net                                   20.527ms asymm 10 
13:  2a01:8100:2000:6000::19                              20.716ms asymm 11 
14:  2a01:8100:2000:6000::22                              20.558ms asymm 12 
15:  no reply
16:  no reply
17:  no reply
18:  no reply
19:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500

From NL host (go6lab) openRFC 4890 ✗

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

4/4

Echo small (56B) 26.9ms

4/4

Echo 1500B (DF) 27.3ms

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	2a00:8642:42::2	1.1ms	0%	AS203993	GNA-DC1-AS - S.J.M. Steffann, NL
2	*	-	0%*	-
3	2a00:1ca8:1::194	3.3ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
4	2a03:3f40::10:41	4.2ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
5	ix-et-9-1-2.tcore1.ad1-amsterdam.ipv6.as6453.net 2a01:3e0:30:1::1	7.6ms	0%	AS6453	AS6453 - TATA COMMUNICATIONS (AMERICA) INC, US
6	if-bundle-2-2.qcore1.ad1-amsterdam.ipv6.as6453.net 2a01:3e0:701::7	4.4ms	0%	AS6453	AS6453 - TATA COMMUNICATIONS (AMERICA) INC, US
7	if-bundle-51-2.qcore1.av2-amsterdam.ipv6.as6453.net 2a01:3e0:701::f	5.2ms	50%	AS6453	AS6453 - TATA COMMUNICATIONS (AMERICA) INC, US
8	2a01:3e0:ff40:20::b	15.9ms	0%	AS6453	AS6453 - TATA COMMUNICATIONS (AMERICA) INC, US
9	2001:668:0:2:ffff:0:5995:8d0a	23.6ms	0%	AS3257	GTT-BACKBONE - GTT Communications Inc., US
10	cotendo-gw.ip6.gtt.net 2001:668:0:3::a000:222	23.2ms	0%	AS3257	GTT-BACKBONE - GTT Communications Inc., US
11	2a01:8100:2000:6000::19	25.9ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
12	2a01:8100:2000:6000::22	26.7ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
13	*	-	0%	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-

Rate-limited ICMPv6: hop 7 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.019ms pmtu 1500
 1:  2a00:8642:42::2                                       0.868ms 
 1:  2a00:8642:42::2                                       1.191ms 
 2:  no reply
 3:  2a00:1ca8:1::194                                      2.677ms 
 4:  2a03:3f40::10:41                                      3.912ms 
 5:  ix-et-9-1-2.tcore1.ad1-amsterdam.ipv6.as6453.net      7.026ms 
 6:  if-bundle-2-2.qcore1.ad1-amsterdam.ipv6.as6453.net    5.204ms 
 7:  if-bundle-51-2.qcore1.av2-amsterdam.ipv6.as6453.net   7.799ms 
 8:  2a01:3e0:ff40:20::b                                  20.879ms asymm 16 
 9:  2001:668:0:2:ffff:0:5995:8d0a                        25.410ms asymm 16 
10:  cotendo-gw.ip6.gtt.net                               26.234ms asymm 13 
11:  2a01:8100:2000:6000::19                              28.139ms asymm 14 
12:  2a01:8100:2000:6000::22                              44.181ms asymm 15 
13:  no reply
14:  no reply
15:  no reply
16:  no reply
17:  no reply
18:  no reply
19:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500

From ITA host (Karsolink) echo onlyRFC 4890 ✗

filter likely at: destination AS39729 (REGISTER-AS) · min PMTU on path: 1500

4/4

Echo small (56B) 9.7ms

0/4

Echo 1500B (DF) -

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	*	-	-	-
2	*	-	-	-
3	*	-	-	-
4	dada-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:a5d2:9550:113	9.6ms	0%	-	NA
5	2a01:8100:2000:6000::19	9.7ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
6	2a01:8100:2000:6000::22	9.5ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
7	*	-	0%	-
8	*	-	-	-
9	*	-	-	-
10	*	-	-	-
11	*	-	-	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-

tracepath -6

 1?: [LOCALHOST]                        0.030ms pmtu 1500
 1:  karsolink-01.net.karsolink.com                        0.282ms 
 2:  2a12:d8c0:109f:121::a1                                0.604ms 
 3:  no reply
 4:  dada-v6.mix-it.net                                    9.910ms asymm  5 
 5:  2a01:8100:2000:6000::19                               9.882ms asymm  6 
 6:  2a01:8100:2000:6000::22                               9.889ms asymm  7 
 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
     Too many hops: pmtu 1500
     Resume: pmtu 1500

From SLO host (6connect) openRFC 4890 ✗

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

4/4

Echo small (56B) 10.4ms

4/4

Echo 1500B (DF) 10.4ms

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	*	-	-	-
3	*	-	60%	-
4	e0-1.core1.lju1.he.net 2001:470:1:5be::1	1.9ms	-	AS6939	HURRICANE - Hurricane Electric LLC, US
5	*	-	-	-
6	*	-	90%	-
7	*	-	-	-
8	dada-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:a5d2:9550:113	10.4ms	0%	-	NA
9	2a01:8100:2000:6000::19	10.5ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
10	2a01:8100:2000:6000::22	10.6ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
11	*	-	0%	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-

Rate-limited ICMPv6: hop 3, hop 6 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.019ms pmtu 9000
 1:  fw1-lju.6connect.com                                  0.600ms 
 1:  fw1-lju.6connect.com                                  0.505ms 
 2:  no reply
 3:  2a03:a100:0:201:1::1                                  1.937ms 
 4:  2a03:a100:0:201:1::1                                  1.133ms pmtu 1500
 4:  e0-1.core1.lju1.he.net                                2.563ms 
 5:  no reply
 6:  port-channel1.core1.zag2.he.net                       6.102ms 
 7:  no reply
 8:  dada-v6.mix-it.net                                   11.980ms asymm  7 
 9:  2a01:8100:2000:6000::19                              10.742ms asymm  8 
10:  2a01:8100:2000:6000::22                              11.079ms asymm  9 
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
     Too many hops: pmtu 1500

From SLO host (T-2) openRFC 4890 ✗

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

4/4

Echo small (56B) 34.6ms

4/4

Echo 1500B (DF) 34.7ms

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	*	-	0%*	-
2	2a01:260:1::225	11.9ms	0%*	AS34779	T-2-AS - T-2, d.o.o., SI
3	2a01-260-1-1--9c.core6.t-2.net 2a01:260:1:1::9c	11.4ms	0%*	AS34779	T-2-AS - T-2, d.o.o., SI
4	hurricane-electric.nikhef.nlsix.net 2001:7f8:13::a500:6939:1	44.7ms	0%*	-	NA
5	be7.core2.fra2.he.net 2001:470:e:18::2	49.2ms	0%	AS6939	HURRICANE - Hurricane Electric LLC, US
6	be7.core2.fra2.he.net 2001:470:e:18::2	49.2ms	30%	AS6939	HURRICANE - Hurricane Electric LLC, US
7	*	-	0%	-
8	be1.core1.mil2.he.net 2001:470:e:dd::1	43.8ms	0%	AS6939	HURRICANE - Hurricane Electric LLC, US
9	*	-	0%	-
10	*	-	-	-
11	dada-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:a5d2:9550:113	31.9ms	0%	-	NA
12	2a01:8100:2000:6000::22	42.0ms	0%	AS39729	REGISTER-AS - REGISTER S.P.A., IT
13	*	-	0%	-
14	*	-	10%	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-

Rate-limited ICMPv6: hop 6, hop 14 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.026ms pmtu 1500
 1:  2a01:261:313:b814::1                                  0.987ms 
 2:  2a01:260:1::225                                       2.879ms 
 3:  2a01-260-1-1--9a.core6.t-2.net                        2.182ms 
 4:  2a01-260-1-1--39.core6.t-2.net                        3.581ms asymm  3 
 5:  hurricane-electric.nikhef.nlsix.net                  36.405ms asymm  4 
 6:  be3.core4.fra1.he.net                                37.909ms asymm  7 
 7:  be10.core1.zrh2.he.net                               45.096ms asymm  8 
 8:  be1.core1.mil2.he.net                                35.197ms asymm  7 
 9:  be1.core1.mil2.he.net                                34.980ms asymm  7 
10:  dada-v6.mix-it.net                                   30.859ms asymm  7 
11:  2a01:8100:2000:6000::19                              34.393ms asymm  8 
12:  2a01:8100:2000:6000::22                              33.237ms asymm  9 
13:  2a01:8100:2000:6000::22                              36.415ms asymm  9 
14:  no reply
15:  no reply
16:  no reply
17:  no reply
18:  no reply
19:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500