AS39837 - Verein zur Foerderung von NetzwerkkunstPARFC 4890 ✓RPKI -ASPA -

AS overview

Test target: 2a02:3e0::7 · fox.mur.at · address space: PA · prefixes announced: 1

prefix(es): 2a02:3e0::/32

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

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

At least one router inside AS39837's announced prefix replied during the random-target probe. Hop(s): 2a02:3e0:100::4. These are candidate targets for direct testing.

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 NOT honored. Forged PTB had no effect (filtered en route or stack ignored it). (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)

Rate-limited ICMPv6: hop 4, hop 8, hop 9 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.019ms pmtu 1500
 1:  _gateway                                              0.870ms 
 1:  _gateway                                              0.552ms 
 2:  sox-pn.sox.rs                                         0.548ms 
 3:  2001:7f8:1e:8::3d                                     0.808ms asymm  2 
 4:  ae8-930.RT.IRX.VIE.AT.retn.net                       11.538ms asymm  3 
 5:  wien21.aco.net                                       11.563ms asymm  3 
 6:  2001:628:1600:1003::1                                14.628ms asymm  4 
 7:  2001:628:1600:1003::2                                15.979ms asymm  5 
 8:  2a02:3e0:100::4                                      19.965ms asymm  6 
 9:  fox.mur.at                                           18.046ms reached
     Resume: pmtu 1500 hops 9 back 7 

From DE host (Berlin)   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-0-0-13-178.gw01.ber01.as59645.net                  0.628ms 
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.484ms 
 2:  ae0-2453.cr10.ber01.lwlcom.net                        1.002ms 
 3:  ae0-40.cr10.muc02.lwlcom.net                         11.824ms 
 4:  ae0-10.cr10.muc01.lwlcom.net                         11.943ms 
 5:  wien1.aco.net                                        17.471ms 
 6:  2001:628:1600:1003::1                                20.350ms 
 7:  2001:628:1600:1003::2                                20.912ms 
 8:  2a02:3e0:100::4                                      21.861ms 
 9:  fox.mur.at                                           21.942ms reached
     Resume: pmtu 1500 hops 9 back 9 

From DE host (Düsseldorf)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

Rate-limited ICMPv6: hop 11, hop 12 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.019ms pmtu 1500
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.718ms 
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.191ms 
 2:  ae0-101.cr10.dus02.lwlcom.net                         0.515ms 
 3:  ae0-40.cr10.dus05.lwlcom.net                          0.420ms 
 4:  ae0-90.cr11.dus01.lwlcom.net                          0.688ms 
 5:  ae0-10.cr10.dus06.lwlcom.net                          0.838ms 
 6:  ae0-40.cr10.fra06.lwlcom.net                          4.353ms 
 7:  ae0-20.cr10.muc01.lwlcom.net                         14.287ms asymm  5 
 8:  wien1.aco.net                                        20.748ms asymm  6 
 9:  2001:628:1600:1003::1                                23.224ms asymm  7 
10:  2001:628:1600:1003::2                                23.648ms asymm  8 
11:  2a02:3e0:100::4                                     353.848ms asymm  9 
12:  fox.mur.at                                           25.939ms reached
     Resume: pmtu 1500 hops 12 back 10 

From NL host (go6lab)   openRFC 4890 ✗

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

Path (traceroute + mtr + PTR)

Rate-limited ICMPv6: hop 5, hop 6, hop 7, hop 8, hop 12 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.056ms pmtu 1500
 1:  2a00:8642:42::2                                       4.690ms 
 1:  2a00:8642:42::2                                       3.169ms 
 2:  no reply
 3:  2a00:1ca8:1::194                                      6.504ms 
 4:  2a03:3f40::10:41                                      4.000ms 
 5:  2001:b28:3ff::1b1b:0:1                               29.864ms 
 6:  be9.core4.fra1.he.net                                33.320ms asymm  4 
 7:  be8.core1.prg1.he.net                                38.122ms asymm  5 
 8:  be3.core1.vie1.he.net                                44.721ms asymm  6 
 9:  2001:470:2dd::2                                      40.094ms asymm  7 
10:  2001:628:1600:1003::1                                42.767ms asymm  8 
11:  2001:628:1600:1003::2                                43.724ms asymm  9 
12:  2a02:3e0:100::4                                      43.826ms asymm 10 
13:  fox.mur.at                                           47.653ms reached
     Resume: pmtu 1500 hops 13 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 5 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.050ms pmtu 1500
 1:  no reply
 2:  2a12:d8c0:109f:121::a1                                0.658ms 
 3:  2a12:d8c0:101f:6::1                                  10.066ms 
 4:  no reply
 5:  no reply
 6:  2001:470:2dd::2                                      16.281ms 
 7:  2001:628:1600:1003::1                                19.564ms 
 8:  2001:628:1600:1003::2                                19.561ms 
 9:  2a02:3e0:100::4                                      20.352ms 
10:  fox.mur.at                                           21.130ms reached
     Resume: pmtu 1500 hops 10 back 10 

From SLO host (6connect)   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]                        0.020ms pmtu 9000
 1:  fw1-lju.6connect.com                                  0.545ms 
 1:  fw1-lju.6connect.com                                  0.489ms 
 2:  no reply
 3:  no reply
 4:  2a00:ee0:1:15::2                                      1.573ms asymm  3 
 5:  2a00:ee0:1:15::2                                     18.198ms pmtu 1500
 5:  2a11:4142:2002::                                      1.241ms asymm  6 
 6:  r2-vie1-at.as5405.net                                 7.291ms asymm  9 
 7:  et9-4096.r2-vie2-at.as5405.net                        7.455ms asymm  8 
 8:  wien21.aco.net                                        8.207ms asymm  4 
 9:  2001:628:1600:1003::1                                12.206ms asymm  6 
10:  2001:628:1600:1003::2                               250.743ms asymm  7 
11:  2a02:3e0:100::4                                     358.653ms asymm  8 
12:  fox.mur.at                                          323.143ms reached
     Resume: pmtu 1500 hops 12 back 9 

From SLO host (T-2)   openRFC 4890 ✓

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

Path (traceroute + mtr + PTR)

Rate-limited ICMPv6: hop 8, hop 9 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.027ms pmtu 1500
 1:  no reply
 2:  2a01:260:1::225                                      11.971ms 
 3:  2a01-260-1-1--9c.core6.t-2.net                        2.609ms 
 4:  2a01-260-1-1--25.core6.t-2.net                        6.794ms 
 5:  2a01-260-1-1--2a.core6.t-2.net                        5.251ms asymm  4 
 6:  2001:628:1600:1003::1                                12.005ms 
 7:  2001:628:1600:1003::2                                12.103ms 
 8:  2a02:3e0:100::4                                      13.419ms 
 9:  2a02:3e0:100::4                                      13.394ms asymm  8 
10:  fox.mur.at                                           13.465ms reached
     Resume: pmtu 1500 hops 10 back 9