AS31042 - SERBIA-BROADBAND-AS Serbia BroadBand-Srpske Kablovske mrezePI/PARFC 4890 ✓RPKI ✓ 2/2ASPA -

AS overview

Test target: 2a03:87c0::1 · static prefix probe · address space: mixed · prefixes announced: 2

prefix(es): 2a00:1dd8::/29, 2a03:87c0::/29

SOX peering

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

At least one router inside AS31042's announced prefix replied during the random-target probe. Hop(s): 2a00:1dd8:2:1::, 2a00:1dd8:2:24::1, 2a00:1dd8:2:25::1, 2a00:1dd8:2:26::1, 2a00:1dd8:2:27::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 2026-09-23T11:08:49Z

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)

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

tracepath -6

 1?: [LOCALHOST]                        0.012ms pmtu 1500
 1:  _gateway                                              0.652ms 
 1:  _gateway                                              0.470ms 
 2:  sbb.sox.rs                                            1.720ms 
 3:  bg-ne-m-0-be16.sbb.rs                                 1.546ms 
 4:  bg-ne-m-10-be1.sbb.rs                                 1.965ms 
 5:  bg-tp-c-1-po1.sbb.rs                                  1.127ms reached
     Resume: pmtu 1500 hops 5 back 5 

From DE host (Berlin)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.043ms pmtu 1500
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.495ms 
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.496ms 
 2:  ae0-2453.cr10.ber01.lwlcom.net                        1.175ms 
 3:  ae0-150.cr10.fra01.lwlcom.net                        10.504ms asymm  7 
 4:  ae0-100.cr10.fra02.lwlcom.net                        10.453ms asymm  8 
 5:  ae0-10.cr10.fra06.lwlcom.net                         10.157ms asymm  7 
 6:  no reply
 7:  sbb.sox.rs                                           41.493ms asymm  9 
 8:  bg-tp-m-0-be3.sbb.rs                                 40.989ms asymm 10 
 9:  bg-ne-m-10-be1.sbb.rs                                41.531ms asymm 11 
10:  bg-tp-c-1-po2.sbb.rs                                 41.266ms reached
     Resume: pmtu 1500 hops 10 back 12 

From DE host (Düsseldorf)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

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

tracepath -6

 1?: [LOCALHOST]                        0.021ms pmtu 1500
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  1.604ms 
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.278ms 
 2:  eth1-0-12-h5594.edge5-dus1.bb.wiit.network            1.048ms 
 3:  no reply
 4:  lag30.core3-dus1.bb.wiit.network                      0.324ms 
 5:  lag2.core1-dus-ix.bb.wiit.network                     0.540ms 
 6:  de-fra-r-1-hu6-1.sbb.rs                               5.048ms 
 7:  2a03:dd80:1:4d::                                     34.826ms asymm  9 
 8:  2a03:dd80:1:8::1                                     31.716ms 
 9:  2a03:dd80:2:3::1                                     32.991ms asymm  8 
10:  bg-ne-m-0-be16.sbb.rs                                32.169ms asymm  9 
11:  bg-ne-m-10-be1.sbb.rs                                32.410ms asymm 10 
12:  bg-tp-c-1-po1.sbb.rs                                 31.893ms reached
     Resume: pmtu 1500 hops 12 back 11 

From NL host (go6lab)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

Rate-limited ICMPv6: hop 14, hop 17, hop 18 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.035ms pmtu 1500
 1:  2a00:8642:42::2                                       6.654ms 
 1:  2a00:8642:42::2                                       2.236ms 
 2:  gw.friends.steffann.nl                                2.561ms 
 3:  2a00:1ca8:1::194                                      4.289ms 
 4:  2a03:3f40::10:41                                      3.126ms 
 5:  2001:978:2:40::3:1                                    7.658ms 
 6:  be3457.ccr41.ams03.atlas.cogentco.com                 7.798ms 
 7:  be2950.ccr42.fra05.atlas.cogentco.com                14.370ms 
 8:  be7944.ccr22.muc03.atlas.cogentco.com                19.727ms 
 9:  be5456.ccr81.vie01.atlas.cogentco.com                25.416ms 
10:  be9463.ccr21.bts01.atlas.cogentco.com                25.128ms 
11:  be3263.ccr31.bud01.atlas.cogentco.com                26.987ms 
12:  be8848.rcr61.tsr02.atlas.cogentco.com                31.319ms 
13:  2001:978:0:6fff::2                                   36.306ms asymm  7 
14:  2a03:dd80:1:4::                                      46.711ms asymm  7 
15:  no reply
16:  2a03:dd80:2:3::1                                     50.110ms asymm  8 
17:  bg-tp-m-0-be3.sbb.rs                                 45.449ms asymm  9 
18:  bg-tp-m-10-be2.sbb.rs                                46.062ms asymm 10 
19:  bg-tp-c-1-po1.sbb.rs                                 50.360ms reached
     Resume: pmtu 1500 hops 19 back 11 

From ITA host (Karsolink)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

Rate-limited ICMPv6: hop 3, hop 4, hop 7, hop 11 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.030ms pmtu 1500
 1:  no reply
 2:  2a12:d8c0:109f:121::a1                                0.386ms 
 3:  2a12:d8c0:109f:106::a2                                3.331ms 
 4:  2a03:b020:1:51::a                                    10.458ms 
 5:  rt.irx.vie.at.retn.net                               11.765ms 
 6:  as31042.zurich.sbb.rs                                24.289ms 
 7:  no reply
 8:  2a03:dd80:1:8::1                                     38.487ms 
 9:  2a03:dd80:2:3::1                                     30.558ms 
10:  bg-tp-m-0-be3.sbb.rs                                 39.091ms 
11:  bg-ne-m-10-be1.sbb.rs                                36.169ms 
12:  bg-tp-c-1-po1.sbb.rs                                 39.144ms reached
     Resume: pmtu 1500 hops 12 back 12 

From SLO host (6connect)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.027ms pmtu 9000
 1:  fw1-lju.6connect.com                                  0.620ms 
 1:  fw1-lju.6connect.com                                  0.632ms 
 2:  ccr-to-fw-ccr1-gw-lju.6connect.com                    0.991ms 
 3:  2a03:a100:0:201:1::1                                  0.805ms 
 4:  2a03:a100:0:201:1::1                                  0.864ms pmtu 1500
 4:  2001:7f8:46::2:1215                                  10.009ms 
 5:  2a03:dd80:2::1                                       10.127ms 
 6:  bg-tp-m-0-be3.sbb.rs                                  9.870ms 
 7:  bg-tp-m-10-be1.sbb.rs                                10.089ms 
 8:  bg-tp-c-1-po1.sbb.rs                                  9.414ms reached
     Resume: pmtu 1500 hops 8 back 8 

From SLO host (T-2)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

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

tracepath -6

 1?: [LOCALHOST]                        0.092ms pmtu 1500
 1:  2a01:261:313:b814::1                                  1.178ms 
 1:  2a01:261:313:b814::1                                  0.996ms 
 2:  2a01:260:1::225                                       9.510ms 
 3:  2a01-260-1-1--9c.core6.t-2.net                        2.695ms 
 4:  2001:7f8:46::2:1215                                  10.722ms 
 5:  2a03:dd80:2::1                                       11.449ms 
 6:  bg-ne-m-0-be16.sbb.rs                                12.277ms 
 7:  bg-tp-m-10-be1.sbb.rs                                12.473ms 
 8:  bg-tp-c-1-po1.sbb.rs                                 39.707ms reached
     Resume: pmtu 1500 hops 8 back 8