AS202988 ZIGA-KRALJ - Ziga Kralj

AS overview

Test target: 2a0f:85c1:e11::1 · static prefix probe · address space: unknown · prefixes announced: 1

prefix(es): 2a0f:85c1:e11::/48

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
`2a0f:85c1:e11::1`	prb	✓	✗	?	?	✓	✓	✗	?	?	✓	✓	✗	?	?	✓

RPKI & ASPA

0 of 1 prefix(es) covered by a valid ROA, 1 not-found.

Prefix	RPKI state	Reason	Covering VRP(s)
`2a0f:85c1:e11::/48`	- not-found	no covering VRP

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

We probed 15 arbitrary IPv6 address(es) inside AS202988's announced prefix(es). No router inside the prefix responded. The deepest visible hop was 2a0f:85c2:7::38f at hop 12 - that router answers ICMPv6 Echo. This is not in AS202988's announced prefix; operationally it's the AS-edge / peering interface (often on a SIX 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`	`2a0f:85c1:e11::1`	`icmp6-echo`	honored	2026-05-30T10:35:56Z
karsolink	`2a12:d8c0:105a:9001::a154`	`2a0f:85c1:e11::1`	`icmp6-echo`	no_echo	2026-05-30T10:45:28Z
odin	`2607:fae0:a000::42`	`2a0f:85c1:e11::1`	`icmp6-echo`	honored	2026-05-30T10:35:26Z

Attempt log (go6lab):

icmp6-echo → honored (size_before=1360, size_after=None)
dns-tcp → no_tcp: connect failed: [Errno 101] Network is unreachable
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 101] Network is unreachable
tls → no_tcp: TLS connect failed
http → no_tcp: tcp/80 not open

Attempt log (odin):

icmp6-echo → honored (size_before=1260, size_after=None): natural Echo Reply at 1300B was already split into IPv6 fragments without our PTB intervention -- the destination's stack has a cached path MTU below 1300B from a previously-honored ICMPv6 Type 2, which is itself evidence that this destination honors PTB on this path.
dns-tcp → no_tcp: connect failed: [Errno 101] Network is unreachable
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): AS7578, AS6939, AS207841.

From go6lab (echo_only/Type-2=honored) the path enters AS207841 at hop 8; from karsolink (echo_only/Type-2=no_echo) the same hop is in AS7578. Last common AS: AS202988. The disagreement is most likely rooted in one of those two transit ASes.
From go6lab (echo_only/Type-2=honored) the path enters AS50673 at hop 4; from odin (echo_only/Type-2=honored) the same hop is in AS6939. Last common AS: AS202988. The disagreement is most likely rooted in one of those two transit ASes.
From karsolink (echo_only/Type-2=no_echo) the path enters AS7578 at hop 8; from odin (echo_only/Type-2=honored) the same hop is in AS6939. Last common AS: AS202988. 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	*	-		- (no IP)
4	2001:470:1:5be::1	AS6939	HURRICANE - Hurricane Electric LLC, US	? no_response
5	2001:470:0:578::1	AS6939	HURRICANE - Hurricane Electric LLC, US	? no_response
6	*	-		- (no IP)
7	*	-		- (no IP)
8	2001:470:e:44::1	AS6939	HURRICANE - Hurricane Electric LLC, US	? no_response
9	2001:470:e:41::2	AS6939	HURRICANE - Hurricane Electric LLC, US	? no_response
10	*	-		- (no IP)
11	2001:7f8:17::3:3347:1	-	NA	? no_response
12	2a0f:85c2:7::38f	AS207841	INFERNO - Inferno Communications Ltd, GB	? no_response
13	*	-		- (no IP)
14	*	-		- (no IP)
15	*	-		- (no IP)
16	*	-		- (no IP)
17	*	-		- (no IP)
18	*	-		- (no IP)
19	*	-		- (no IP)
20	2a0f:85c1:e11::1	AS202988	ZIGA-KRALJ - Ziga Kralj, 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.

From NL host (go6lab) echo onlyRFC 4890 ✓

filter likely at: destination AS202988 (ZIGA-KRALJ) · min PMTU on path: 1476

4/4

Echo small (56B) 39.4ms

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	2a00:8642:42::3	0.7ms	0%	AS203993	STEFFANN-DC-AS - S.J.M. Steffann, NL
2	*	-	0%*	-
3	2a00:1ca8:1::194	2.6ms	10%	AS50673	Serverius-as - Serverius Holding B.V., NL
4	2a03:3f40::10:33	10.8ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
5	2001:7f8:1:0:a500:13:7409:1	6.5ms	0%	-	NA
6	e35.ams-nikhef-cr9.globalsecurelayer.com 2401:3cc0:10:50::1:1bc	14.9ms	0%	AS7578	GSL - Global Secure Layer, AU
7	e31.lon-thn-cr8.globalsecurelayer.com 2401:3cc0::4:48a	11.0ms	0%	AS7578	GSL - Global Secure Layer, AU
8	ebr1.ix1.inferno.net.uk 2a0f:85c0::1	10.8ms	0%	AS207841	INFERNO - Inferno Communications Ltd, GB
9	2a0f:85c2:7::38f	11.9ms	0%	AS207841	INFERNO - Inferno Communications Ltd, GB
10	*	-	-	-
11	*	-	-	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	2a0f:85c1:e11::1	42.3ms	0%	AS202988	ZIGA-KRALJ - Ziga Kralj, SI

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

tracepath -6

 1?: [LOCALHOST]                        0.031ms pmtu 1476
 1:  2a00:8642:42::3                                       1.288ms 
 1:  2a00:8642:42::3                                       1.554ms 
 2:  gw.friends.steffann.nl                                2.402ms 
 3:  2a00:1ca8:1::194                                      3.284ms 
 4:  2a03:3f40::10:33                                      5.316ms 
 5:  2001:7f8:1:0:a500:13:7409:1                           6.611ms 
 6:  e35.ams-nikhef-cr9.globalsecurelayer.com             15.470ms asymm 12 
 7:  e31.lon-thn-cr8.globalsecurelayer.com                11.764ms asymm  8 
 8:  ebr1.ix1.inferno.net.uk                              10.943ms asymm  7 
 9:  2a0f:85c2:7::38f                                     12.173ms asymm  8 
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     Too many hops: pmtu 1476
     Resume: pmtu 1476

From ITA host (Karsolink) echo only

filter likely at: destination AS202988 (ZIGA-KRALJ) · min PMTU on path: 1476

4/4

Echo small (56B) 59.1ms

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	*	-	0%*	-
2	2a12:d8c0:109f:121::a1	0.4ms	0%*	AS204471	KARSOLINK - 2S Computers SRL, IT
3	2a12:d8c0:101f:103::1	8.6ms	0%	AS204471	KARSOLINK - 2S Computers SRL, IT
4	gslnetworks-AS137409.mix-it.net 2001:7f8:b:100:1d1:a513:7409:247	8.6ms	0%	-	NA
5	e33.fra-eqxfr5-bb4.globalsecurelayer.com 2401:3cc0:10:50::1:2c7	25.3ms	0%	AS7578	GSL - Global Secure Layer, AU
6	po400.fra-eqxfr5-cr6.globalsecurelayer.com 2401:3cc0:10:50::1:1b6	25.1ms	0%	AS7578	GSL - Global Secure Layer, AU
7	e36.ams-eqxam5-cr5.globalsecurelayer.com 2401:3cc0:10:50::1:362	28.3ms	0%	AS7578	GSL - Global Secure Layer, AU
8	e35.ams-nikhef-cr9.globalsecurelayer.com 2401:3cc0:10:50::1:1bc	28.3ms	0%	AS7578	GSL - Global Secure Layer, AU
9	e31.lon-thn-cr8.globalsecurelayer.com 2401:3cc0::4:48a	27.8ms	0%	AS7578	GSL - Global Secure Layer, AU
10	ebr1.ix1.inferno.net.uk 2a0f:85c0::1	102.9ms	0%	AS207841	INFERNO - Inferno Communications Ltd, GB
11	2a0f:85c2:7::38f	102.6ms	0%	AS207841	INFERNO - Inferno Communications Ltd, GB
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	2a0f:85c1:e11::1	59.5ms	-	AS202988	ZIGA-KRALJ - Ziga Kralj, SI

tracepath -6

 1?: [LOCALHOST]                        0.133ms pmtu 1500
 1:  karsolink-01.net.karsolink.com                        0.863ms 
 1:  karsolink-01.net.karsolink.com                        0.707ms 
 2:  2a12:d8c0:109f:121::a1                                0.988ms 
 3:  2a12:d8c0:101f:103::1                                 8.748ms 
 4:  gslnetworks-as137409.mix-it.net                       8.910ms 
 5:  e33.fra-eqxfr5-bb4.globalsecurelayer.com             26.682ms asymm 11 
 6:  po400.fra-eqxfr5-cr6.globalsecurelayer.com           25.524ms asymm 12 
 7:  e36.ams-eqxam5-cr5.globalsecurelayer.com             28.363ms asymm 11 
 8:  e35.ams-nikhef-cr9.globalsecurelayer.com             29.133ms asymm 12 
 9:  e31.lon-thn-cr8.globalsecurelayer.com                28.928ms asymm 10 
10:  ebr1.ix1.inferno.net.uk                              30.581ms asymm  6 
11:  2a0f:85c2:7::38f                                     30.840ms asymm  7 
12:  2a0f:85c2:7::38f                                     27.474ms pmtu 1476
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     Too many hops: pmtu 1476

From SLO host (6connect) echo onlyRFC 4890 ✓

filter likely at: destination AS202988 (ZIGA-KRALJ) · min PMTU on path: 1476

4/4

Echo small (56B) 63.9ms

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	fw1-lju.6connect.com 2607:fae0:a000::2	0.3ms	0%*	AS8038	6CONNECT - 6connect, Inc., US
2	*	-	-	-
3	*	-	10%	-
4	e0-1.core1.lju1.he.net 2001:470:1:5be::1	1.9ms	0%	AS6939	HURRICANE - Hurricane Electric LLC, US
5	100ge0-0-0-5.core1.vie1.he.net 2001:470:0:578::1	7.3ms	0%	AS6939	HURRICANE - Hurricane Electric LLC, US
6	*	-	-	-
7	*	-	40%	-
8	be2.core4.lon2.he.net 2001:470:e:44::1	33.3ms	30%	AS6939	HURRICANE - Hurricane Electric LLC, US
9	be4.core2.lon3.he.net 2001:470:e:41::2	31.4ms	0%	AS6939	HURRICANE - Hurricane Electric LLC, US
10	*	-	-	-
11	lonap.lagrange.cloud 2001:7f8:17::3:3347:1	29.6ms	0%	-	NA
12	2a0f:85c2:7::38f	29.7ms	0%	AS207841	INFERNO - Inferno Communications Ltd, GB
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-
20	2a0f:85c1:e11::1	60.1ms	0%	AS202988	ZIGA-KRALJ - Ziga Kralj, SI

Rate-limited ICMPv6: hop 3, hop 7, hop 8 (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                                  0.403ms 
 1:  fw1-lju.6connect.com                                  0.575ms 
 2:  no reply
 3:  2a03:a100:0:201:1::1                                  0.838ms 
 4:  e0-1.core1.lju1.he.net                                2.283ms 
 5:  100ge0-0-0-5.core1.vie1.he.net                        8.158ms 
 6:  no reply
 7:  be47.core3.par2.he.net                               28.720ms 
 8:  be2.core4.lon2.he.net                                32.400ms 
 9:  be4.core2.lon3.he.net                                32.191ms 
10:  no reply
11:  lonap.lagrange.cloud                                 29.580ms 
12:  2a0f:85c2:7::38f                                     29.524ms 
13:  2a0f:85c2:7::38f                                     29.707ms pmtu 1476
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     Too many hops: pmtu 1476