AS3313 INET-AS BT Italia S.p.A.

IPv6 prefix announced, but nothing inside is responding yet. AS3313 announces 1 IPv6 prefix(es) to the global routing table - that’s the part that BGP and our route-server scrape confirm. But our active discovery (curated hostnames, holder-derived domains, authoritative DNS NS/SOA/MX, certificate-transparency hostnames, RIPE Atlas, RDAP, IPv6 Hitlist) found no ICMPv6-responsive host inside the prefix on either vantage, and a yarrp pass against random addresses inside the prefix produced zero in-prefix hops (no router on the path through the AS replied with Time-Exceeded for any random target). That combination usually means the announcement is configured but the addresses inside aren’t in active use yet. The BGP route is there; the operational deployment is still ahead.

AS overview

Test target: 2a03:cf00::1 · (no live host found) · address space: mixed · prefixes announced: 1

prefix(es): 2a03:cf00::/32

MIX-IT / NAMEX / MINAP / TOP-IX / VSIX / EQUINIX-MILAN / BGPX-ROME / NAMEX-BARI / PCIX / DECIX-PALERMO peering

Not an MIX-IT / NAMEX / MINAP / TOP-IX / VSIX / EQUINIX-MILAN / BGPX-ROME / NAMEX-BARI / PCIX / DECIX-PALERMO member, but our traceroute path crosses the MIX-IT / NAMEX / MINAP / TOP-IX / VSIX / EQUINIX-MILAN / BGPX-ROME / NAMEX-BARI / PCIX / DECIX-PALERMO LAN from ITA host (Karsolink) - reached via an MIX-IT / NAMEX / MINAP / TOP-IX / VSIX / EQUINIX-MILAN / BGPX-ROME / NAMEX-BARI / PCIX / DECIX-PALERMO-resident transit operator.

RPKI & ASPA

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

Prefix	RPKI state	Reason	Covering VRP(s)
`2a03:cf00::/32`	- not-found	no covering VRP

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

We probed 15 arbitrary IPv6 address(es) inside AS3313's announced prefix(es). No router inside the prefix responded. The deepest visible hop was 2001:2034:a:122::1 at hop 10 - that router answers ICMPv6 Echo. This is not in AS3313'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 active test inconclusive: no Echo Reply to 1300-byte probe.
method: ICMPv6 Echo + forged PTB, tested 2026-05-25T12:32:40Z

Failure detail — what to grep in your logs

vantage	our source	your target	method	result	tested (UTC)
go6lab	`2a00:8642:42::75`	`2a03:cf00::1`	`icmp6-echo`	no_echo	2026-05-25T12:32:40Z
karsolink	`2a12:d8c0:105a:9001::a154`	`2a03:cf00::1`	`icmp6-echo`	no_echo	2026-05-25T12:40:56Z
odin	`2607:fae0:a000::42`	`2a03:cf00::1`	`icmp6-echo`	no_echo	2026-05-25T12:32:18Z

Attempt log (go6lab):

icmp6-echo → no_echo: no Echo Reply to 1300-byte probe
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: timed out
tls → no_tcp: TLS connect failed
http → no_tcp: tcp/80 not open

Attempt log (odin):

icmp6-echo → no_echo: no Echo Reply to 1300-byte probe
dns-tcp → no_tcp: connect failed: timed out
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.

From NL host (go6lab) transit only unreachable

filter likely at: past AS1299 (TWELVE99) · min PMTU on path: 1500

0/4

Echo small (56B) -

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	0.9ms	0%	AS203993	STEFFANN-DC-AS - S.J.M. Steffann, NL
2	*	-	-	-
3	2a00:1ca8:1::194	3.1ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
4	2a03:3f40::10:41	2.6ms	0%	AS50673	Serverius-as - Serverius Holding B.V., NL
5	*	-	-	-
6	*	-	-	-
7	2001:978:3::26	3.9ms	0%	AS174	COGENT-174 - Cogent Communications, LLC, US
8	2001:2034:a:94	4.0ms	0%	-
9	*	-	-	-
10	mno-b3-link.ip.twelve99.net 2001:2034:a:1f9::1	29.8ms	0%	AS1299	TWELVE99 - Arelion Sweden AB, SE
11	*	-	-	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-
20	*	-	-	-
21	*	-	-	-
22	*	-	-	-
23	*	-	-	-
24	*	-	-	-

tracepath -6

 1?: [LOCALHOST]                        0.029ms pmtu 1500
 1:  2a00:8642:42::3                                       0.917ms 
 1:  2a00:8642:42::3                                       1.172ms 
 2:  gw.friends.steffann.nl                                1.787ms 
 3:  2a00:1ca8:1::194                                      2.654ms 
 4:  2a03:3f40::10:41                                      2.281ms 
 5:  no reply
 6:  no reply
 7:  2001:978:3::ca                                        4.643ms asymm  6 
 8:  adm-bb2-link.ip.twelve99.net                          3.933ms asymm  7 
 9:  no reply
10:  mno-b3-link.ip.twelve99.net                          29.465ms 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
20:  no reply
21:  no reply
22:  no reply
23:  no reply
24:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500

From ITA host (Karsolink) transit only unreachable

filter likely at: no path · min PMTU on path: 1500

0/4

Echo small (56B) -

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	*	-	0%*	-
3	2a12:d8c0:101f:103::1	8.5ms	20%	AS204471	KARSOLINK - 2S Computers SRL, IT
4	btitalia2-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:a5d0:8968:150	9.8ms	0%	-	NA
5	*	-	-	-
6	*	-	-	-
7	*	-	-	-
8	*	-	-	-
9	*	-	-	-
10	*	-	-	-
11	*	-	-	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-
20	*	-	-	-
21	*	-	-	-
22	*	-	-	-
23	*	-	-	-
24	*	-	-	-

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

tracepath -6

 1?: [LOCALHOST]                        0.029ms pmtu 1500
 1:  karsolink-01.net.karsolink.com                        0.431ms 
 2:  2a12:d8c0:109f:121::a1                                0.677ms 
 3:  2a12:d8c0:101f:103::1                                 9.017ms 
 4:  btitalia2-v6.mix-it.net                              10.410ms 
 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
20:  no reply
21:  no reply
22:  no reply
23:  no reply
24:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500

From SLO host (6connect) transit only unreachable

filter likely at: no path · min PMTU on path: 1500

0/4

Echo small (56B) -

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	*	-	0%*	-
3	2a03:a100:0:201:1::1	0.7ms	80%	AS56635	XENYA - XENYA inzeniring, proizvodnja in trgovina, d.o.o. Ljubljana, SI
4	e0-1.core1.lju1.he.net 2001:470:1:5be::1	2.8ms	60%	AS6939	HURRICANE - Hurricane Electric LLC, US
5	*	-	-	-
6	port-channel1.core1.zag2.he.net 2001:470:0:2ea::2	3.6ms	70%	AS6939	HURRICANE - Hurricane Electric LLC, US
7	*	-	-	-
8	bt.topix.it 2001:7f8:23:ffff::2b	13.5ms	0%	-	NA
9	*	-	0%	-
10	*	-	-	-
11	*	-	-	-
12	*	-	-	-
13	*	-	-	-
14	*	-	-	-
15	*	-	-	-
16	*	-	-	-
17	*	-	-	-
18	*	-	-	-
19	*	-	-	-
20	*	-	-	-
21	*	-	-	-
22	*	-	-	-
23	*	-	-	-
24	*	-	-	-

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]                        0.029ms pmtu 1500
 1:  fw1-lju.6connect.com                                  1.514ms 
 1:  fw1-lju.6connect.com                                  0.482ms 
 2:  no reply
 3:  2a03:a100:0:201:1::1                                  1.220ms 
 4:  e0-1.core1.lju1.he.net                                2.638ms 
 5:  no reply
 6:  port-channel1.core1.zag2.he.net                       9.486ms 
 7:  no reply
 8:  btitalia2-v6.mix-it.net                              11.594ms asymm  7 
 9:  2a02:4d80:200:f053::2                                12.853ms asymm  7 
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
20:  no reply
21:  no reply
22:  no reply
23:  no reply
24:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500