Arch Linux

Freed

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From: China

Registered: 2020-02-01

Posts: 59

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machine A can ping machine B, but machine B cannot ping machine A

I have two machine connected by a LAN cable. one:

$ ip a
...
2: enp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 7c:10:c9:22:96:78 brd ff:ff:ff:ff:ff:ff
    inet 169.254.35.1/16 brd 169.254.255.255 scope global enp4s0
       valid_lft forever preferred_lft forever

another:

$ ip a
5: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether b6:41:d4:f6:d1:20 brd ff:ff:ff:ff:ff:ff
    inet 169.254.35.142/16 brd 169.254.255.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::a24a:fce7:8515:ba8a/64 scope link
       valid_lft forever preferred_lft forever

In the machine 169.254.35.1, I can ping 169.254.35.142. But in the machine 169.254.35.142, I cannot ping 169.254.35.1.

What happened?

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ugjka

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From: Latvia

Registered: 2014-04-01

Posts: 1,868

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Re: machine A can ping machine B, but machine B cannot ping machine A

After what "what happened?"?

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seth

Member

Registered: 2012-09-03

Posts: 60,792

Re: machine A can ping machine B, but machine B cannot ping machine A

I cannot ping 169.254.35.1

isn't an error message, please don't paraphrase, https://bbs.archlinux.org/viewtopic.php?id=57855
Also there're obviously more NICs on the 142 host, post the complete outputs of

ip a; ip r

on both hosts.
Are those the only hosts in the segment? Can you post 169.254.35.1 from other hosts? Can 169.254.35.142 ping other hosts?

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Freed

Member

From: China

Registered: 2020-02-01

Posts: 59

Website

Re: machine A can ping machine B, but machine B cannot ping machine A

Hey, this is full messages:

In machine A:

$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 fe80::38a:2962:be5b:57a5/64 scope link
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 7c:10:c9:22:96:78 brd ff:ff:ff:ff:ff:ff
    inet 169.254.35.1/16 brd 169.254.255.255 scope global enp4s0
       valid_lft forever preferred_lft forever
3: wlo1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 28:d0:ea:38:fd:5b brd ff:ff:ff:ff:ff:ff
    altname wlp0s20f3
    inet 211.86.144.129/22 brd 211.86.147.255 scope global dynamic noprefixroute wlo1
       valid_lft 2025sec preferred_lft 2025sec
    inet6 fe80::d143:a256:a17:45ec/64 scope link
       valid_lft forever preferred_lft forever
    inet6 fe80::d628:50c5:7139:e55e/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
$ ping 169.254.35.142
PING 169.254.35.142 (169.254.35.142) 56(84) bytes of data.
64 bytes from 169.254.35.142: icmp_seq=1 ttl=64 time=0.157 ms
64 bytes from 169.254.35.142: icmp_seq=2 ttl=64 time=0.059 ms
^C
--- 169.254.35.142 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1026ms
rtt min/avg/max/mdev = 0.059/0.108/0.157/0.049 ms
$ ip r
default via 211.86.147.254 dev wlo1 proto dhcp src 211.86.144.129 metric 600
127.0.0.0/8 dev lo proto dhcp scope host src 127.0.0.1 metric 1001
169.254.0.0/16 dev enp4s0 proto kernel scope link src 169.254.35.1
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
211.86.144.0/22 dev wlo1 proto kernel scope link src 211.86.144.129 metric 600

In machine B:

$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: sit0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN group default qlen 1000
    link/sit 0.0.0.0 brd 0.0.0.0
3: can0: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10
    link/can
4: can1: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10
    link/can
5: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether b6:41:d4:f6:d1:20 brd ff:ff:ff:ff:ff:ff
    inet 169.254.35.142/16 brd 169.254.255.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::a24a:fce7:8515:ba8a/64 scope link
       valid_lft forever preferred_lft forever
$ ping 168.254.35.1
PING 168.254.35.1 (168.254.35.1): 56 data bytes

^C
--- 168.254.35.1 ping statistics ---
4 packets transmitted, 0 packets received, 100% packet loss
$ ip r
default dev eth0 scope link src 169.254.35.142 metric 1001005
169.254.0.0/16 dev eth0 scope link src 169.254.35.142 metric 1005

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An adherent of hacker culture and open source.

seth

Member

Registered: 2012-09-03

Posts: 60,792

Re: machine A can ping machine B, but machine B cannot ping machine A

2: sit0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN group default qlen 1000
    link/sit 0.0.0.0 brd 0.0.0.0

Why is there a 6in4 tunnel and does it work w/o?

3: can0: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10
    link/can
4: can1: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10
    link/can

raspberry pi?

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Freed

Member

From: China

Registered: 2020-02-01

Posts: 59

Website

Re: machine A can ping machine B, but machine B cannot ping machine A

raspberry pi

Right, machine A is archlinux and machine B is a board like raspberry pi.

Why is there a 6in4 tunnel and does it work w/o?

I am silly with network How to disable 6in4 tunnel?

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seth

Member

Registered: 2012-09-03

Posts: 60,792

Re: machine A can ping machine B, but machine B cannot ping machine A

machine B is a board like raspberry pi.
… I am silly with network How to disable 6in4 tunnel?

By not adding/enabling it - this doesn't just happen.
https://wiki.archlinux.org/title/IPv6_t … oker_setup explains how this /can/ be setup, what happens on your banana pi or whatever is a different question.

And that's also a major problem, the target system isn't archlinux and apparently neither you nor obviously any of us has any idea how it's configured.
Consult the help channels for that platform.

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