AS199324 dodonet DODONET S.R.L.

AS overview

Test target: 2a00:54e0::d0d0 · ns1.dodonet.it · address space: PA · prefixes announced: 1

prefix(es): 2a00:54e0::/32

Targets & per-vantage-point probe results (2 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
`2a00:54e0::d0d0` ns1.dodonet.it	NS	✓	✓	?	?	✓	✓	✓	?	?	✓	✓	✓	?	?	✓
`2a00:54e0::d0d1` ns2.dodonet.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 2018-03-16. IPv6 LAN: 2001:7f8:b:100:1d1:a519:9324:23. Locations: -.

RPKI & ASPA

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

Prefix	RPKI state	Reason	Covering VRP(s)
`2a00:54e0::/32`	✓ valid	matched VRP (correct origin, length within maxLength)	AS199324 /32 maxLen 32 (ripe)

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

At least one router inside AS199324's announced prefix replied during the random-target probe. Hop(s): 2a00:54e0:255::5:1, 2a00:54e0:255::f:3. 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`	`2a00:54e0::d0d0`	`icmp6-echo`	honored	2026-05-30T12:42:39Z
karsolink	`2a12:d8c0:105a:9001::a154`	`2a00:54e0::d0d0`	`icmp6-echo`	no_echo	2026-05-30T12:45:37Z
odin	`2607:fae0:a000::42`	`2a00:54e0::d0d0`	`icmp6-echo`	honored	2026-05-30T12:42:29Z

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 shrink
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=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

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	inconclusive	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): AS199324, AS41327, AS6939.

From go6lab (open/Type-2=honored) the path enters an opaque hop at hop 10; from karsolink (open/Type-2=no_echo) the same hop is in AS199324. Last common AS: AS199324. The disagreement is most likely rooted in one of those two transit ASes.
From go6lab (open/Type-2=honored) the path enters AS41327 at hop 4; from odin (open/Type-2=honored) the same hop is in AS6939. Last common AS: AS199324. 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	*	-		- (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	2001:7f8:b:100:1d1:a519:9324:23	-	NA	? no_response
9	2a00:54e0:255::5:1	AS199324	dodonet - DODONET S.R.L., IT	? no_response
10	2a00:54e0:255::f:3	AS199324	dodonet - DODONET S.R.L., IT	? no_response
11	2a00:54e0:dcdc:0:b::5	AS199324	dodonet - DODONET S.R.L., IT	? no_response
12	2a00:54e0::d0d0	AS199324	dodonet - DODONET S.R.L., IT	? 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

4/4

Echo small (56B) 31.0ms

4/4

Echo 1500B (DF) 31.1ms

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	1.3ms	0%	AS203993	STEFFANN-DC-AS - S.J.M. Steffann, NL
2	gw.friends.steffann.nl 2a00:8642:1000:f000::1	2.0ms	0%*	AS203993	STEFFANN-DC-AS - S.J.M. Steffann, NL
3	speed-ix.fibertelecom.it 2001:7f8:b7::a504:1327:1	3.1ms	0%	-	NA
4	2a03:b020::226	19.4ms	0%	AS41327	FIBERTELECOM-AS - Fiber Telecom S.p.A., IT
5	2a03:b020:1:47::b	19.1ms	0%	AS41327	FIBERTELECOM-AS - Fiber Telecom S.p.A., IT
6	2a00:54e0:255::5:1	30.3ms	0%	AS199324	dodonet - DODONET S.R.L., IT
7	2a00:54e0:255::f:3	29.9ms	0%	AS199324	dodonet - DODONET S.R.L., IT
8	2a00:54e0:dcdc:0:b::5	30.4ms	0%	AS199324	dodonet - DODONET S.R.L., IT
9	ns1.dodonet.it 2a00:54e0::d0d0	31.0ms	0%	AS199324	dodonet - DODONET S.R.L., IT

tracepath -6

 1?: [LOCALHOST]                        0.033ms pmtu 1500
 1:  2a00:8642:42::3                                       1.423ms 
 1:  2a00:8642:42::3                                       1.846ms 
 2:  no reply
 3:  speed-ix.fibertelecom.it                              3.887ms 
 4:  2a03:b020::226                                       19.534ms 
 5:  2a03:b020:1:47::b                                    18.879ms asymm  9 
 6:  2a00:54e0:255::5:1                                   30.106ms asymm 10 
 7:  2a00:54e0:255::f:3                                   30.811ms asymm 11 
 8:  2a00:54e0:dcdc:0:b::5                                31.761ms asymm 12 
 9:  ns1.dodonet.it                                       31.728ms !A
     Resume: pmtu 1500

From ITA host (Karsolink) open

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

4/4

Echo small (56B) 21.9ms

4/4

Echo 1500B (DF) 22.0ms

yes

Type 1 dest-unreach

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	*	-	0%*	-
2	2a12:d8c0:109f:121::a1	0.4ms	0%*	AS204471	KARSOLINK - 2S Computers SRL, IT
3	2a12:d8c0:101f:103::1	8.4ms	40%	AS204471	KARSOLINK - 2S Computers SRL, IT
4	2001:7f8:b9::24:1	29.9ms	90%	-	NA
5	*	-	90%	-
6	*	-	30%	-
7	2a00:6d42:0:2:9b::26	9.8ms	10%	AS31034	ARUBA-ASN - Aruba S.p.A., IT
8	2a02:29e0:255::3:1993:2	9.7ms	0%	-	NA
9	2a00:54e0:255::5:1	20.6ms	0%	AS199324	dodonet - DODONET S.R.L., IT
10	2a00:54e0:255::f:3	21.7ms	0%	AS199324	dodonet - DODONET S.R.L., IT
11	2a00:54e0:dcdc:0:b::5	21.8ms	0%	AS199324	dodonet - DODONET S.R.L., IT
12	ns1.dodonet.it 2a00:54e0::d0d0	21.8ms	0%	AS199324	dodonet - DODONET S.R.L., IT

Rate-limited ICMPv6: hop 3, hop 4, hop 5, hop 6, hop 7 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.030ms pmtu 1500
 1:  karsolink-01.net.karsolink.com                        0.642ms 
 1:  karsolink-01.net.karsolink.com                        1.078ms 
 2:  2a12:d8c0:109f:121::a1                                0.896ms 
 3:  2a12:d8c0:101f:103::1                                 8.992ms 
 4:  2001:7f8:b9::24:1                                    19.263ms asymm  8 
 5:  no reply
 6:  er2-hu0-0-0-20.ip6.it3.aruba.it                      11.942ms asymm  7 
 7:  2a00:6d42:0:2:9b::26                                 10.140ms asymm  4 
 8:  2a02:29e0:255::3:1993:2                              10.148ms asymm  4 
 9:  2a00:54e0:255::5:1                                   22.374ms asymm  5 
10:  2a00:54e0:255::f:3                                   21.882ms asymm  6 
11:  2a00:54e0:dcdc:0:b::5                                22.366ms asymm  7 
12:  ns1.dodonet.it                                       22.314ms !A
     Resume: pmtu 1500

From SLO host (6connect) openRFC 4890 ✓

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

4/4

Echo small (56B) 24.3ms

4/4

Echo 1500B (DF) 24.2ms

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	*	-	0%*	-
3	2a03:a100:0:201:1::1	1.3ms	20%	AS56635	XENYA - XENYA inzeniring, proizvodnja in trgovina, d.o.o. Ljubljana, SI
4	e0-1.core1.lju1.he.net 2001:470:1:5be::1	2.3ms	30%	AS6939	HURRICANE - Hurricane Electric LLC, US
5	*	-	-	-
6	port-channel1.core1.zag2.he.net 2001:470:0:2ea::2	3.7ms	50%	AS6939	HURRICANE - Hurricane Electric LLC, US
7	*	-	-	-
8	dodonet-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:a519:9324:23	11.9ms	0%	-	NA
9	2a00:54e0:255::5:1	22.8ms	0%	AS199324	dodonet - DODONET S.R.L., IT
10	2a00:54e0:255::f:3	23.7ms	0%	AS199324	dodonet - DODONET S.R.L., IT
11	2a00:54e0:dcdc:0:b::5	24.1ms	0%	AS199324	dodonet - DODONET S.R.L., IT
12	ns1.dodonet.it 2a00:54e0::d0d0	24.2ms	0%	AS199324	dodonet - DODONET S.R.L., IT

Rate-limited ICMPv6: hop 3, hop 4, hop 6 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.031ms pmtu 1500
 1:  fw1-lju.6connect.com                                  0.559ms 
 1:  fw1-lju.6connect.com                                  0.435ms 
 2:  ccr-to-fw-ccr1-gw-lju.6connect.com                    0.638ms 
 3:  2a03:a100:0:201:1::1                                  0.792ms 
 4:  e0-1.core1.lju1.he.net                                2.120ms 
 5:  no reply
 6:  port-channel1.core1.zag2.he.net                       5.361ms 
 7:  no reply
 8:  dodonet-v6.mix-it.net                                12.199ms 
 9:  2a00:54e0:255::5:1                                   23.393ms 
10:  2a00:54e0:255::f:3                                   24.105ms 
11:  2a00:54e0:dcdc:0:b::5                                24.368ms 
12:  ns1.dodonet.it                                       24.327ms !A
     Resume: pmtu 1500