AS34779 - T-2PARFC 4890 ✓RPKI ✓ 8/8ASPA -

AS overview

Test target: 2a01:260:1:2::72 · www.t-2.net · address space: PA · prefixes announced: 8

prefix(es): 2a01:263::/32, 2a01:260::/32, 2a01:264::/32, 2a01:262::/32, 2a01:265::/32, 2a01:266::/32, 2a01:267::/32, 2a01:261::/32

SIX peering

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

At least one router inside AS34779's announced prefix replied during the random-target probe. Hop(s): 2a01:261:313:b814::1. 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 NOT honored. Forged PTB had no effect (filtered en route or stack ignored it). (TLS handshake + forged PTB)
• NL host (go6lab): Type 2 honored. Forged PTB accepted; next response shrunk. (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). (TLS handshake + forged PTB)
• SLO host (T-2): Type 2 honored. Forged PTB accepted; next response shrunk. (ICMPv6 Echo + forged PTB)

Why they disagree - different probe methods: These vantages picked different probe methods, so their verdicts are not directly comparable. The active test tries methods in order (icmp6-echo → dns-tcp → tls → http) and stops at the first that produces a definitive verdict; if the chosen method differs, the underlying evidence differs too. Most often this is because the path PMTU on one vantage is below 1500 B, so the natural Echo Reply is already fragmented and the icmp6-echo method falls through to a TCP-based one. This is largely a measurement artifact, not a destination-behaviour difference.

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]                        0.015ms pmtu 1500
 1:  _gateway                                              0.487ms 
 1:  _gateway                                              0.671ms 
 2:  sox-pn.sox.rs                                         0.448ms 
 3:  2001:7f8:1e:8::3d                                     0.569ms asymm  2 
 4:  ae8-930.RT.IRX.VIE.AT.retn.net                       12.826ms asymm  3 
 5:  2001:7f8:30:0:2:1:3:4779                             17.566ms asymm  8 
 6:  2a01-260-1-1--d.core6.t-2.net                        18.195ms asymm  7 
 7:  2a01:260:1:1::274                                    17.624ms asymm  9 
 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
     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)

Rate-limited ICMPv6: hop 15 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.022ms pmtu 1500
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  1.055ms 
 1:  xe-0-0-13-178.gw01.ber01.as59645.net                  0.828ms 
 2:  ae0-2453.cr10.ber01.lwlcom.net                        1.454ms 
 3:  ae3-90.cr10.ham01.lwlcom.net                          5.235ms 
 4:  ae0-50.cr11.ham01.lwlcom.net                          5.468ms 
 5:  2a00:c380:f000::4b                                    5.878ms asymm  4 
 6:  ae4-2087.dus10.core-backbone.com                     12.041ms asymm  5 
 7:  ae21-2071.fra10.core-backbone.com                    11.312ms asymm  5 
 8:  ae2-2021.fra20.core-backbone.com                     11.433ms asymm  4 
 9:  ae6-2003.nbg20.core-backbone.com                     12.544ms asymm  6 
10:  ae2-2032.muc20.core-backbone.com                     14.965ms asymm  7 
11:  ae1-2028.vie10.core-backbone.com                     20.629ms asymm  8 
12:  2a01:4a0:1338:115::2                                 88.075ms 
13:  2a01-260-1-1--d.core6.t-2.net                        31.676ms asymm 11 
14:  2a01:260:1:1::274                                    32.158ms asymm 13 
15:  no reply
16:  no reply
17:  no reply
18:  no reply
19:  no reply
20:  no reply
21:  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]                        0.008ms pmtu 1500
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.373ms 
 1:  xe-0-0-12-142.gw01.dus01.as59645.net                  0.324ms 
 2:  ipv6.decix-dusseldorf.core1.dus1.he.net               7.431ms asymm  3 
 3:  no reply
 4:  be6.core2.ams2.he.net                                 8.827ms asymm  6 
 5:  t-2.interxionfra11.nlsix.net                         33.481ms asymm 11 
 6:  2a01:260:1:1::274                                    32.633ms asymm 12 
 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
     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]                        0.040ms pmtu 1500
 1:  ???                                                   1.710ms 
 1:  ???                                                   2.875ms 
 2:  no reply
 3:  speed-ix.he.net                                       9.383ms 
 4:  no reply
 5:  be6.core2.ams2.he.net                                 7.478ms 
 6:  t-2.interxionfra11.nlsix.net                         43.477ms 
 7:  2a01:260:1:1::274                                    41.321ms 
 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
     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)

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:  karsolink-01.net.karsolink.com                        1.165ms 
 1:  karsolink-01.net.karsolink.com                        0.910ms 
 2:  2a12:d8c0:109f:121::a1                                0.882ms 
 3:  2a12:d8c0:101f:6::1                                  10.973ms 
 4:  no reply
 5:  100ge0-0-0-20.core1.vie1.he.net                      22.241ms 
 6:  2001:7f8:30:0:2:1:3:4779                             19.769ms 
 7:  2a01-260-1-1--d.core6.t-2.net                        45.025ms asymm 11 
 8:  2a01:260:1:1::274                                    40.868ms asymm 11 
 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
     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 3 (loss between 5% and 95% across mtr cycles - the router replies but only sometimes).

tracepath -6

 1?: [LOCALHOST]                        0.025ms pmtu 9000
 1:  fw1-lju.6connect.com                                  0.868ms 
 1:  fw1-lju.6connect.com                                  0.676ms 
 2:  no reply
 3:  2a03:a100:0:201:1::1                                  1.294ms 
 4:  2a03:a100:0:201:1::1                                  1.136ms pmtu 1500
 4:  six.t-2.si                                           13.728ms 
 5:  2a01:260:1:1::274                                     1.343ms asymm  6 
 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
     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]                        0.028ms pmtu 1500
 1:  no reply
 2:  2a01:260:1::225                                       3.277ms 
 3:  2a01-260-1-1--9c.core6.t-2.net                        3.548ms 
 4:  2a01:260:1:1::274                                     2.543ms 
 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
     Too many hops: pmtu 1500
     Resume: pmtu 1500