AS56488 EISIT Eis S.r.l.

AS overview

Test target: 2a12:2544::1 · static prefix probe · address space: unknown · prefixes announced: 2

prefix(es): 2a12:2544::/30, 2a12:2540::/30

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)
Target IP / hostname	Source	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached	ping	1500B	:80	:443	reached
`2a12:2544::1`	prb	✓	✓	?	?	✓	✓	✓	refused	refused	✓	✓	✓	refused	refused	✓

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 2024-04-05. IPv6 LAN: 2001:7f8:b:100:1d1:a5d5:6488:199. Locations: -.

RPKI & ASPA

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

Prefix	RPKI state	Reason	Covering VRP(s)
`2a12:2544::/30`	✓ valid	matched VRP (correct origin, length within maxLength)	AS56488 /29 maxLen 33 (ripe)
`2a12:2540::/30`	✓ valid	matched VRP (correct origin, length within maxLength)	AS56488 /29 maxLen 33 (ripe)

ASPA: this AS has published an ASPA record listing 3 upstream provider(s) that are authorized to propagate routes from it: AS1299, AS3356, AS31034. 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

At least one router inside AS56488's announced prefix replied during the random-target probe. Hop(s): 2a12:2540:1::2, 2a12:2540:1::3, 2a12:2540::1, 2a12:2544::2. 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`	`2a12:2544::1`	`icmp6-echo`	honored	2026-05-30T12:48:32Z
karsolink	`2a12:d8c0:105a:9001::a154`	`2a12:2544::1`	`icmp6-echo`	no_echo	2026-05-30T12:59:06Z
odin	`2607:fae0:a000::42`	`2a12:2544::1`	`icmp6-echo`	honored	2026-05-30T12:48:12Z

Attempt log (go6lab):

icmp6-echo → honored (size_before=1460, size_after=None)
dns-tcp → no_tcp: connect failed: timed out
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 → no_tcp: connect failed: [Errno 111] Connection refused
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 → no_tcp: connect failed: [Errno 111] Connection refused
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	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): AS31500, AS31034, AS50673.

From go6lab (open/Type-2=honored) the path enters AS31500 at hop 5; from karsolink (open/Type-2=no_echo) the same hop is in AS31034. Last common AS: AS56488. 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: AS56488. The disagreement is most likely rooted in one of those two transit ASes.
From karsolink (open/Type-2=no_echo) the path enters an opaque hop at hop 11; from odin (open/Type-2=honored) the same hop is in AS56488. Last common AS: AS56488. 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:a5d3:1034:90	-	NA	? no_response
9	*	-		- (no IP)
10	*	-		- (no IP)
11	2a12:2544::1	AS56488	EISIT - Eis S.r.l., IT	✓ honored

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) 37.4ms

4/4

Echo 1500B (DF) 37.5ms

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	1.4ms	0%	AS203993	STEFFANN-DC-AS - S.J.M. Steffann, NL
2	*	-	0%*	-
3	2a00:1ca8:1::194	3.0ms	10%	AS50673	Serverius-as - Serverius Holding B.V., NL
4	2a03:3f40::10:41	3.3ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
5	2001:b28:3ff::1b1b:0:1	27.0ms	0%	AS31500	GNM-AS - Global Network Management Inc, AG
6	be2.core1.cph1.he.net 2001:470:e:5f::1	26.4ms	20%	AS6939	HURRICANE - Hurricane Electric LLC, US
7	*	-	-	-
8	*	-	-	-
9	aruba-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:a5d3:1034:90	37.7ms	60%	-	NA
10	*	-	90%	-
11	*	-	80%	-
12	gw-dc1.bgy.eis.it 2a12:2544::1	41.3ms	0%	AS56488	EISIT - Eis S.r.l., IT

Rate-limited ICMPv6: hop 3, hop 6, hop 9, hop 10, hop 11 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.031ms pmtu 1500
 1:  2a00:8642:42::3                                       1.738ms 
 1:  2a00:8642:42::3                                       1.196ms 
 2:  gw.friends.steffann.nl                                1.994ms 
 3:  2a00:1ca8:1::194                                      2.482ms 
 4:  2a03:3f40::10:41                                      2.867ms 
 5:  2001:b28:3ff::1b1b:0:1                               27.609ms asymm  6 
 6:  no reply
 7:  no reply
 8:  no reply
 9:  no reply
10:  cr2-hu0-0-0-3-703.ip6.it3.aruba.it                   38.203ms 
11:  er2-hu0-0-0-21.ip6.it3.aruba.it                      38.743ms 
12:  gw-dc1.bgy.eis.it                                    38.358ms reached
     Resume: pmtu 1500 hops 12 back 12

From ITA host (Karsolink) open

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

4/4

Echo small (56B) 9.6ms

4/4

Echo 1500B (DF) 9.7ms

yes

Type 1 dest-unreach

443,80

TCP responds on

Path (traceroute + mtr + PTR)

#	IP / PTR	RTT	mtr loss	AS	AS holder
1	karsolink-01.net.karsolink.com 2a12:d8c0:105a:9001::1	0.4ms	0%*	AS204471	KARSOLINK - 2S Computers SRL, IT
2	2a12:d8c0:109f:121::a1	0.4ms	0%*	AS204471	KARSOLINK - 2S Computers SRL, IT
3	2a12:d8c0:101f:103::1	8.5ms	0%	AS204471	KARSOLINK - 2S Computers SRL, IT
4	2001:7f8:b9::24:1	18.2ms	20%	-	NA
5	cr1-hu0-0-0-3-703.ip6.it3.aruba.it 2a00:6d42::1:0:1:32	12.6ms	30%	AS31034	ARUBA-ASN - Aruba S.p.A., IT
6	*	-	30%	-
7	gw-dc1.bgy.eis.it 2a12:2544::1	11.8ms	0%	AS56488	EISIT - Eis S.r.l., IT

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

tracepath -6

 1?: [LOCALHOST]                        0.016ms pmtu 1500
 1:  karsolink-01.net.karsolink.com                        0.341ms 
 1:  no reply
 2:  2a12:d8c0:109f:121::a1                                0.746ms 
 3:  2a12:d8c0:101f:103::1                                 8.867ms 
 4:  2001:7f8:b9::24:1                                    18.412ms asymm  8 
 5:  cr1-hu0-0-0-3-703.ip6.it3.aruba.it                   14.041ms asymm  6 
 6:  no reply
 7:  gw-dc1.bgy.eis.it                                    10.875ms reached
     Resume: pmtu 1500 hops 7 back 8

From SLO host (6connect) openRFC 4890 ✓

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

4/4

Echo small (56B) 11.0ms

4/4

Echo 1500B (DF) 11.0ms

yes

Type 1 dest-unreach

443,80

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	2a03:a100:0:201:1::1	0.6ms	10%	AS56635	XENYA - XENYA inzeniring, proizvodnja in trgovina, d.o.o. Ljubljana, SI
4	e0-1.core1.lju1.he.net 2001:470:1:5be::1	2.0ms	10%	AS6939	HURRICANE - Hurricane Electric LLC, US
5	*	-	-	-
6	port-channel1.core1.zag2.he.net 2001:470:0:2ea::2	4.1ms	0%	AS6939	HURRICANE - Hurricane Electric LLC, US
7	*	-	-	-
8	aruba-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:a5d3:1034:90	319.6ms	20%	-	NA
9	*	-	30%	-
10	*	-	30%	-
11	gw-dc1.bgy.eis.it 2a12:2544::1	12.4ms	0%	AS56488	EISIT - Eis S.r.l., IT

Rate-limited ICMPv6: hop 3, hop 4, hop 8, hop 9, hop 10 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.025ms pmtu 1500
 1:  fw1-lju.6connect.com                                  0.496ms 
 1:  fw1-lju.6connect.com                                  0.497ms 
 2:  no reply
 3:  no reply
 4:  e0-1.core1.lju1.he.net                                2.628ms 
 5:  no reply
 6:  port-channel1.core1.zag2.he.net                       3.704ms 
 7:  no reply
 8:  aruba-v6.mix-it.net                                  11.424ms asymm  7 
 9:  cr1-hu0-0-0-3-704.ip6.it3.aruba.it                   14.384ms asymm  7 
10:  no reply
11:  gw-dc1.bgy.eis.it                                    16.765ms reached
     Resume: pmtu 1500 hops 11 back 10