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Topic # 239355 13-Jul-2018 11:40
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Switched over my fibre RSP (Retail Service Provider) from Bigpipe,200/20,MikroTik RB850Gx2 to 2Degrees Broadband,Max/max, FRITZ!Box 7560.  I changed the router due to reachability issues for some WWW sites. And its always easier to diagnose issues if you use their issued router.   I have turned off the FRITZ!Box DHCP server, Wi-Fi AP, and renumbered it to because the home network is not exactly greenfields...


Things have gone swimmingly for the Window 10 box, but Linux (3.16.0-5-amd64 #1 SMP Debian 3.16.51) isn't faring so well.


Addresses and routes are appearing but packets aren't flowing:


ip -6 addr dev eth1


2: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
inet6 2406:e006:28a6:0:960c:6dff:fe80:61b/64 scope global noprefixroute dynamic
valid_lft 2528064sec preferred_lft 540864sec
inet6 2406:e006:1c6:1:960c:6dff:fe80:61b/64 scope global noprefixroute dynamic
valid_lft 7110sec preferred_lft 3510sec
inet6 fe80::960c:6dff:fe80:61b/64 scope link
valid_lft forever preferred_lft forever


ip -6 route list dev eth1


2406:e006:1c6:1::/64 proto ra metric 1
2406:e006:1c6::/48 via fe80::eadf:70ff:fe31:3452 proto ra metric 1
2406:e006:28a6::/64 proto ra metric 1
fe80::/64 proto kernel metric 256 mtu 1492
default via fe80::eadf:70ff:fe31:3452 proto static metric 1024


I can reach the default next hop:


ping6 fe80::eadf:70ff:fe31:3452%eth1
PING fe80::eadf:70ff:fe31:3452%eth1(fe80::eadf:70ff:fe31:3452) 56 data bytes
64 bytes from fe80::eadf:70ff:fe31:3452: icmp_seq=1 ttl=64 time=0.997 ms
64 bytes from fe80::eadf:70ff:fe31:3452: icmp_seq=2 ttl=64 time=0.676 ms
64 bytes from fe80::eadf:70ff:fe31:3452: icmp_seq=3 ttl=64 time=0.752 ms
64 bytes from fe80::eadf:70ff:fe31:3452: icmp_seq=4 ttl=64 time=0.719 ms


But traceroute6 doesn't get very far:


traceroute6 -n 2001:8b0:0:30::666:102
traceroute to 2001:8b0:0:30::666:102 (2001:8b0:0:30::666:102) from 2406:e006:28a6:0:960c:6dff:fe80:61b, 30 hops max, 24 byte packets
1 * * *
2 * * *
3 * * *


etc. etc.




So Windows 10 is working just fine in exactly the same network, but Debian (perhaps due to greater compliance or misconfiguration in the past) is struggling in a way that it didn't when using the MikroTik.


Any suggestions or requests for additional information gratefully received.





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28 posts

+1 received by user: 4


Reply # 2056614 15-Jul-2018 19:12
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The IPv4 default gateway attracts the old value (, from where, IHNFI.



As noted the LAN is a shambles of bits and pieces accumulated over time as interest, need and resources allowed.  I got a  Netgate SG-1000, on special and played around with it for a while.  


It seemed like a nice, reliable home for the DHCP Server on the LAN after I stopped using it as a fully operational router.  



That's where I changed the default router for DHCP requests from .251 to .249


But that didn't change the behaviour above.  Then I discovered:



The LAN interface static IPv4 configuration gives the option of an IPv4 upstream gateway on the LAN, useful for downloading updates to the device without a WAN Internet connection.


But perhaps this was over-riding the DHCP server gateway setting?


Actually no.  I belatedly discovered "DHCP Static Mappings for this Interface" which provides a wide range of bespoke values for individual devices, including... gateway addresses, and sure enough, that's where the feral .251 was.


Leave it blank, and it picks up the general DHCP gateway value.  Success.




As for the IPv6 issue, I plugged Jimmy directly into the Fritz!Box, replacing the cable at the same time, and shortly afterward:


jimmy:~$ traceroute6
traceroute to (2001:8b0:0:30::666:102) from 2406:e006:1c6:1:960c:6dff:fe80:61b, 30 hops max, 24 byte packets
1 2406:e006:1c6:1:eadf:70ff:fe31:3452 (2406:e006:1c6:1:eadf:70ff:fe31:3452) 1.693 ms 0.988 ms 1.137 ms
2 2406:e000:2801:c::1 (2406:e000:2801:c::1) 2.929 ms 1.047 ms 1.383 ms
3 * * *
4 (2001:1900:2100::20e) 165.898 ms 165.89 ms 165.923 ms
5 (2001:1900:2100::20d) 166.772 ms 168.209 ms 166.734 ms
6 (2001:1900::4:6) 285.455 ms 285.752 ms 286.839 ms
7 (2001:8b0:0:53::48) 296.725 ms 294.944 ms 294.465 ms
8 (2001:8b0:0:89a::1) 297.477 ms 295.105 ms 294.637 ms
9 (2001:8b0:0:30::51bb:1e02) 296.059 ms 296.139 ms 303.872 ms
10 (2001:8b0:0:30::666:102) 298.493 ms 297.001 ms 297.626 ms

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