Interesting IPv6 problem, rtac88u, Merlin 380.57, 1500 v 1452 MTU

PabloAbonia

Regular Contributor
IPv6 traceroute from router or any network device fails at first hop.
I can ping the external router wan /128 address IPv6 address with any packet up to 1452 bytes in size, in spite of eth0 being listed with an 1500 MTU, on a cable modem (SB6141) with no evidence of PPPoE which is more often associated with DSL rather than cable modem.

Netalyzr is also complaining about it having difficulty with handling fragmented packets via IPv6.

There are no problems for IPv4 at all, and I've included a sample IPv6 traceroute below.

Thanks for your help,

Pablo

traceroute to www.v6.facebook.com (2a03:2880:20:8f08:face:b00c:0:1), 30 hops max, 16 byte packets
1 * * *
2 2605:a000:0:4::4:b3 (2605:a000:0:4::4:b3) 8.230 ms 17.593 ms 10.350 ms
3 2605:a000:0:4::4:4575 (2605:a000:0:4::4:4575) 10.735 ms 8.286 ms 11.813 ms
4 2605:a000:0:4::74 (2605:a000:0:4::74) 12.202 ms 22.042 ms 11.966 ms
5 2001:1998:0:4::1a6 (2001:1998:0:4::1a6) 22.875 ms 22.762 ms 23.985 ms
6 2001:1998::9 (2001:1998::9) 71.938 ms 73.268 ms 71.862 ms
7 2001:1998::66:109:6:135 (2001:1998::66:109:6:135) 69.107 ms 68.683 ms 75.915 ms
8 2001:1998:0:8::3d2 (2001:1998:0:8::3d2) 69.416 ms 67.942 ms 68.544 ms
9 be26.bb01.lax1.tfbnw.net (2620:0:1cff:dead:beef::b86) 97.861 ms 98.305 ms 98.537 ms
10 ae19.bb03.prn2.tfbnw.net (2620:0:1cff:dead:beef::c49) 97.883 ms 96.428 ms 97.018 ms
11 ae43.dr07.prn2.tfbnw.net (2620:0:1cff:dead:beef::25d) 124.648 ms 100.785 ms 99.388 ms
12 po23.fa06.prn2.tfbnw.net (2620:0:1cff:dead:beef::1929) 99.908 ms 100.460 ms 108.466 ms
13 * * *
14 * * *
15 * * *
16 v6-prod6-shv-08-prn2.facebook.com (2a03:2880:20:8f08:face:b00c:0:1) 97.991 ms 97.316 ms 97.423 ms
 

bbunge

Part of the Furniture
If you are using 6to4 or 6rd your ipv6 MTU may have to be as low as 1200

Sent from my P01M using Tapatalk
 

sfx2000

Part of the Furniture
Is IPv6 being provided by your ISP or thru a 3rd party tunnel broker (HE.net or similar...)?
 

PabloAbonia

Regular Contributor
Forgot. It's native with Time Warner (TWC).

It also causing Netalyzr to randomly fail IPv6 across Windows, MacOS, and Ubuntu.
 

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