AS204471 - KarsolinkPARFC 4890 ✓RPKI ✓ 2/2ASPA ✓

AS overview

Test target: 2a12:d8c0:105a:9001::a133 · one.karsolink.com · address space: PA · prefixes announced: 2

prefix(es): 2a12:d8c0::/32, 2a12:d8c1::/32

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

At least one router inside AS204471's announced prefix replied during the random-target probe. Hop(s): 2a12:d8c0:105a:9001::1. These are candidate targets for direct testing.

ICMPv6 Type 2 (Packet Too Big) acceptance - active test

Type 2 honored. Forged ICMPv6 PTB (MTU=1280) was accepted by the destination's stack: the next 1500-byte Echo Reply arrived split into 2 fragments via the IPv6 Fragment Header.
method: ICMPv6 Echo + forged PTB, tested 2026-09-23T10:36:33Z

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.015ms pmtu 1500
 1:  _gateway                                              0.657ms 
 1:  _gateway                                              0.562ms 
 2:  2001:7f8:1e::4                                        1.070ms 
 3:  2001:7f8:30:0:2:1:0:9002                             35.716ms 
 4:  RT.VSX.PDA.IT.retn.net                               20.922ms 
 5:  GW-AS204471.retn.net                                 28.484ms asymm  6 
 6:  2a12:d8c0:109f:106::a1                               32.283ms 
 7:  2a12:d8c0:109f:121::a2                               32.203ms 
 8:  one.karsolink.com                                    33.159ms reached
     Resume: pmtu 1500 hops 8 back 8 

From DE host (Berlin)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.019ms pmtu 1500
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.460ms 
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.458ms 
 2:  ae0-2453.cr10.ber01.lwlcom.net                        0.813ms 
 3:  retn.bcix.de                                         10.743ms asymm  5 
 4:  RT.VSX.PDA.IT.retn.net                               56.894ms asymm  5 
 5:  GW-AS204471.retn.net                                 22.587ms asymm 11 
 6:  2a12:d8c0:109f:106::a1                               27.116ms asymm 11 
 7:  2a12:d8c0:109f:121::a2                               27.188ms asymm 12 
 8:  one.karsolink.com                                    27.698ms reached
     Resume: pmtu 1500 hops 8 back 13 

From DE host (Düsseldorf)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.022ms pmtu 1500
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.752ms 
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.428ms 
 2:  eth1-0-12-h5594.edge5-dus1.bb.wiit.network            1.274ms 
 3:  no reply
 4:  lag11.core3-dus1.bb.wiit.network                      0.625ms 
 5:  lag0-vl1011.core1-fra-ix.bb.wiit.network              4.901ms 
 6:  lag0-vl1001.core1-nbg-ncd.bb.wiit.network             7.264ms 
 7:  lag0-vl6.core2-nbg-ncd.bb.wiit.network                7.140ms 
 8:  lag0-vl1006.core2-muc2.bb.wiit.network                9.704ms 
 9:  lag0-vl1009.core1-muc-eq3.bb.wiit.network             9.885ms 
10:  lag0-vl1001.core1-pda-vsix.bb.wiit.network           20.685ms 
11:  lag0-vl1001.core1-mil-mix.bb.wiit.network            20.324ms asymm  9 
12:  lag0-vl5.core3-mil-irid.bb.wiit.network              20.169ms asymm  8 
13:  karsolink.minap.it                                   20.430ms asymm  9 
14:  2a12:d8c0:101f:6::2                                  29.929ms asymm 10 
15:  2a12:d8c0:109f:121::a2                               29.712ms asymm 11 
16:  one.karsolink.com                                    30.478ms reached
     Resume: pmtu 1500 hops 16 back 12 

From NL host (go6lab)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.030ms pmtu 1500
 1:  2a00:8642:42::2                                       3.033ms 
 1:  2a00:8642:42::2                                       4.598ms 
 2:  gw.friends.steffann.nl                                3.456ms 
 3:  speed-ix.fibertelecom.it                              5.474ms 
 4:  2a03:b020::226                                       20.211ms 
 5:  2a03:b020:1:51::b                                    19.337ms 
 6:  2a12:d8c0:101f:6::2                                  30.638ms 
 7:  2a12:d8c0:109f:121::a2                               29.014ms 
 8:  one.karsolink.com                                    31.312ms reached
     Resume: pmtu 1500 hops 8 back 8 

From ITA host (Karsolink)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.026ms pmtu 1500
 1:  one.karsolink.com                                     1.527ms reached
 1:  one.karsolink.com                                     1.270ms reached
     Resume: pmtu 1500 hops 1 back 1 

From SLO host (6connect)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.023ms pmtu 9000
 1:  fw1-lju.6connect.com                                  0.773ms 
 1:  fw1-lju.6connect.com                                  0.545ms 
 2:  ccr-to-fw-ccr1-gw-lju.6connect.com                    0.960ms 
 3:  2a03:a100:0:201:1::1                                  0.725ms 
 4:  2a03:a100:0:201:1::1                                  1.219ms pmtu 1500
 4:  e0-1.core1.lju1.he.net                                1.898ms 
 5:  no reply
 6:  port-channel1.core1.zag2.he.net                       4.276ms 
 7:  no reply
 8:  2scomputers-AS204471.mix-it.net                      10.453ms asymm  6 
 9:  2a12:d8c0:101f:6::2                                  19.218ms asymm  7 
10:  2a12:d8c0:109f:121::a2                               18.594ms asymm  8 
11:  one.karsolink.com                                    19.338ms reached
     Resume: pmtu 1500 hops 11 back 10 

From SLO host (T-2)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

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

tracepath -6

 1?: [LOCALHOST]                        0.031ms pmtu 1500
 1:  2a01:261:313:b814::1                                  1.083ms 
 1:  no reply
 2:  2a01:260:1::225                                       4.094ms 
 3:  2a01-260-1-1--9c.core6.t-2.net                        2.454ms 
 4:  hurricane-electric.nikhef.nlsix.net                  38.838ms 
 5:  hurricane-electric.nikhef.nlsix.net                  39.980ms asymm  4 
 6:  be7.core2.fra2.he.net                                42.163ms asymm  5 
 7:  be3.core4.fra1.he.net                                46.624ms 
 8:  be10.core1.zrh2.he.net                               54.606ms 
 9:  be1.core1.mil2.he.net                                39.823ms asymm  7 
10:  karsolink.minap.it                                   36.905ms asymm  7 
11:  2scomputers-AS204471.mix-it.net                      31.841ms asymm  7 
12:  ???                                                  47.808ms asymm  9 
13:  2a12:d8c0:109f:121::a2                               40.657ms asymm  9 
14:  one.karsolink.com                                    46.342ms reached
     Resume: pmtu 1500 hops 14 back 10