AS25761 - FIFTYFIVE-AS 55 IT ServicesPIRFC 4890 ✓RPKI ✓ 1/1ASPA -

AS overview

Test target: 2001:67c:fec:55:170:62:253:88 · ns02.lucesem.at · address space: PI · prefixes announced: 1

prefix(es): 2001:67c:fec::/48

VIX / AAIX / SAIX / TIROL-IX / ERA-IX peering

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

We probed 35 arbitrary IPv6 address(es) inside AS25761's announced prefix(es). No router inside the prefix responded. The deepest visible hop was 2a11:4140::1f at hop 15 - that router answers ICMPv6 Echo. This is not in AS25761'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

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:

• SRB host (SOX, Belgrade): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
• DE host (Berlin): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
• DE host (Düsseldorf): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
• NL host (go6lab): Type 2 NOT honored. Forged PTB had no effect (filtered en route or stack ignored it). (ICMPv6 Echo + forged PTB)
• ITA host (Karsolink): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
• SLO host (6connect): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)
• SLO host (T-2): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)

Why they disagree - path-asymmetric Type 2 filtering: Both vantages used the ICMPv6 Echo + forged-PTB method on the same destination IP, but reached different verdicts. The destination's stack is the same in both cases - so the difference is in the path: a transit AS on one route filters our forged Type 2 (or its return ICMPv6 carrying the embedded packet) while the other route delivers it intact. The vantage that says honored shows what the destination's stack actually does; the one that says not honored shows that the path between us and them drops Type 2.

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 2a01:261:313:b814:2a0:98ff:fe5b:13e4 or src host 2a06:d1c1:10b::cccc or src host 2a06:d1c1:10d::aaaa or src host 2a09:ab81::91 or src host 2a12:d8c0:105a:9001::a154)'

sudo ip6tables -L INPUT -nv | grep -iE 'icmpv6|packet-too-big'
sudo nft list ruleset 2>/dev/null | grep -A1 'icmpv6'

sudo sysctl net.ipv6.conf.all.accept_redirects net.ipv4.ip_no_pmtu_disc net.ipv6.route.mtu_expires

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 or src host 2a09:ab81::91 or src host 2a01:261:313:b814:2a0:98ff:fe5b:13e4 or src host 2a06:d1c1:10a::bbbb or src host 2a06:d1c1:10d::aaaa or src host 2a06:d1c1:10b::cccc)'

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]                        0.012ms pmtu 1500
 1:  _gateway                                             17.862ms 
 1:  _gateway                                              0.293ms 
 2:  2001:7f8:1e::4                                        0.554ms 
 3:  lt000-f.13-f.n11.5506.vie.at.55it.at                 11.400ms asymm  6 
 4:  no reply
 5:  no reply
 6:  no reply
 7:  no reply
 8:  no reply
 9:  no reply
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11:  no reply
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15:  no reply
16:  no reply
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18:  no reply
19:  no reply
20:  no reply
21:  no reply
22:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500 

From DE host (Berlin)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.023ms pmtu 1500
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.396ms 
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.439ms 
 2:  ae0-2453.cr10.ber01.lwlcom.net                        0.912ms 
 3:  ae0-10.cr10.ber03.lwlcom.net                          0.773ms 
 4:  ae0-15.cr11.dtm01.lwlcom.net                          8.693ms asymm  5 
 5:  ae0-20.cr10.dtm01.lwlcom.net                          8.531ms asymm  4 
 6:  ae0-50.cr10.dus02.lwlcom.net                          8.640ms asymm  3 
 7:  ae0-10.cr10.dus01.lwlcom.net                          8.759ms asymm  4 
 8:  ae6-60.cr10.ams01.lwlcom.net                         11.568ms asymm  5 
 9:  as5405.frys-ix.net                                   11.766ms 
10:  r7-ams1-nl.as5405.net                                26.855ms asymm 15 
11:  r7-fra1-de.as5405.net                                26.736ms asymm 14 
12:  r5-fra1-de.as5405.net                                26.770ms asymm 13 
13:  r2-vie1-at.as5405.net                                26.762ms asymm 12 
14:  r2-vie2-at.as5405.net                                26.823ms asymm 11 
15:  r1-vie2-at.as5405.net                                26.890ms asymm 10 
16:  2a11:4140:e002::d                                    28.061ms asymm  6 
17:  no reply
18:  no reply
19:  no reply
20:  no reply
21:  no reply
22:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500 

From DE host (Düsseldorf)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.020ms pmtu 1500
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.365ms 
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.251ms 
 2:  2001:7f8:9e::151d:0:1                                 0.460ms asymm  3 
 3:  r4-fra2-de.as5405.net                                13.985ms asymm 14 
 4:  r7-fra1-de.as5405.net                                14.072ms asymm 13 
 5:  r5-fra1-de.as5405.net                                14.110ms asymm 12 
 6:  r2-vie1-at.as5405.net                                14.172ms asymm 11 
 7:  r2-vie2-at.as5405.net                                14.209ms asymm 10 
 8:  r1-vie2-at.as5405.net                                14.154ms asymm  9 
 9:  2a11:4140:e002::d                                    15.259ms asymm  5 
10:  no reply
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21:  no reply
22:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500 

From NL host (go6lab)   openRFC 4890 ✗

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.036ms pmtu 1500
 1:  2a00:8642:42::2                                       2.437ms 
 1:  2a00:8642:42::2                                       4.541ms 
 2:  gw.friends.steffann.nl                                7.611ms 
 3:  speed-ix.inter.link                                   7.293ms asymm  4 
 4:  r5-ams1-nl.as5405.net                                26.531ms asymm 17 
 5:  r7-ams1-nl.as5405.net                                23.918ms asymm 16 
 6:  r7-fra1-de.as5405.net                                24.852ms asymm 15 
 7:  r5-fra1-de.as5405.net                                24.858ms asymm 14 
 8:  r2-vie1-at.as5405.net                                26.178ms asymm 13 
 9:  r2-vie2-at.as5405.net                                27.653ms asymm 12 
10:  r1-vie2-at.as5405.net                                24.229ms asymm 11 
11:  2a11:4140:e002::d                                    26.818ms asymm  7 
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
     Too many hops: pmtu 1500
     Resume: pmtu 1500 

From ITA host (Karsolink)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.028ms pmtu 1500
 1:  no reply
 2:  no reply
 3:  no reply
 4:  interlink-AS5405.mix-it.net                           8.777ms asymm  5 
 5:  r2-zrh1-ch.as5405.net                                28.912ms asymm 18 
 6:  r3-fra1-de.as5405.net                                28.962ms asymm 17 
 7:  r7-fra1-de.as5405.net                                28.947ms asymm 16 
 8:  r5-fra1-de.as5405.net                                28.932ms asymm 15 
 9:  r2-vie1-at.as5405.net                                28.867ms asymm 14 
10:  r2-vie2-at.as5405.net                                29.169ms asymm 13 
11:  r1-vie2-at.as5405.net                                29.189ms asymm 12 
12:  2a11:4140:e002::d                                    21.211ms asymm  6 
13:  no reply
14:  no reply
15:  no reply
16:  no reply
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18:  no reply
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20:  no reply
21:  no reply
22:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500 

From SLO host (6connect)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

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

tracepath -6

 1?: [LOCALHOST]                        0.027ms pmtu 9000
 1:  fw1-lju.6connect.com                                  0.674ms 
 1:  fw1-lju.6connect.com                                  0.590ms 
 2:  no reply
 3:  2a03:a100:0:201:1::1                                  0.921ms 
 4:  2a03:a100:0:201:1::1                                  0.880ms pmtu 1500
 4:  e0-1.core1.lju1.he.net                                2.269ms 
 5:  no reply
 6:  lt000-f.13-f.n11.5506.vie.at.55it.at                  8.120ms asymm  4 
 7:  no reply
 8:  no reply
 9:  no reply
10:  no reply
11:  no reply
12:  no reply
13:  no reply
14:  no reply
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21:  no reply
22:  no reply
     Too many hops: pmtu 1500

From SLO host (T-2)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

tracepath -6

 1?: [LOCALHOST]                        0.026ms pmtu 1500
 1:  2a01:261:313:b814::1                                  0.725ms 
 2:  2a01:260:1::225                                       4.739ms 
 3:  2a01-260-1-1--9c.core6.t-2.net                        2.300ms 
 4:  2a01-260-1-1--c.core6.t-2.net                         4.452ms 
 5:  2a01-260-1-1--c.core6.t-2.net                         4.703ms asymm  4 
 6:  lt000-f.13-f.n11.5506.vie.at.55it.at                  8.951ms 
 7:  no reply
 8:  no reply
 9:  no reply
10:  no reply
11:  no reply
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22:  no reply
     Too many hops: pmtu 1500
     Resume: pmtu 1500