Can connect to network, can run pacstrap and pacman, but cannot ping

Firestar · 2022-08-22 16:53:09

When I am installing the latest archlinux ISO, I found that I can connect to network

but I cannot ping any website like archlinux.org or even local popular sites like baidu.com

it got no response and 100% packet loss

But when I run pacstrap and pacman to install things, the speed was > 30MB/s

Why?

schard · 2022-08-22 17:06:24

Show us the output of the actual commands.

ewaller · 2022-08-22 17:25:01

Also, please provide clarification. Are you saying that, after the install, you have booted into your new system? And the network does not work from your new installation?

Firestar · 2022-08-23 00:39:36

This is when I was connecting the network (connect succeeded)

This is when I was running ping (100% packet loss)

This is when I ran pacstrap (network speed up to 12.8MiB/s)

Last edited by Firestar (2022-08-25 17:10:49)

Firestar · 2022-08-25 17:11:24

I ran timedatectl set-ntp true

It does not change the ping failure

Last edited by Firestar (2022-08-25 17:14:17)

aldyrius · 2022-08-29 16:29:13

Please post the output of:

ip route; ip addr show

You've not shown any info so far on your layer 3 configuration (other than that your system appears to be using IPv6.) Joining to the Wi-Fi link only means you have succeeded at layer 2, but actually using that link depends greatly on how your network is configured from there. Many wireless routers tend to default to distributing DHCP IPs upon client authentication. Perhaps that happened successfully right before the pacstrap succeeded, but then the link went down.

In general, you can start network troubleshooting each layer after the previously layer is known-good. So in other words if you are confident in the Wi-Fi link, you should:

- Check if you have a valid IP on the interface; does this correspond with what you know about the network you're joining?
- Check if you have a default gateway; if so can you ping it? If not, do you at least get an ARP response back and thus an entry in your ARP cache?
- If you have a valid gateway, have you configured valid DNS?

All above the above could actually be OK in your scenario; it's possible that you really can get to the internet, and a ping is just not a valid test. I noticed that the "PKU" network you joined also has a Visitor version. It's entirely possible that the owner of the network (guessing maybe that's not you) has disabled pings using a firewall upstream. This is a common default for more restrictive firewalls/routers whose owners frown upon users performing network enumeration. A simple one-liner to check for internet connectivity without a ping could be something like:

wget -O - -q http://ipecho.net/plain

But do NOT post the result of that command, for security reasons.

If it is indeed a more corporate-grade firewall blocking pings by default, you could also be subject to a captive portal, etc (like how a mobile phone prompt will often require you to agree to a usage stagement, etc.)

I will let The Internets be your guide from here. This has always been my favorite place to start!

Firestar · 2022-08-31 04:06:57

1. PKU stands for Peking University where I am in, and PKU is our school wifi for students, PKU visitor is our school wifi for visitors which needs phone authentication and is much slower.

2. we have a network portal website its.pku.edu.cn, you can connect to school network on this website if you have connected to any internet, but I cannot ping it

3. my output looks like this

https://s1.328888.xyz/2022/08/31/ac2un.jpg

4. 10.2.xx.xx is our school internet IP but I cannot find the IP on the output above in its.pku.edu.cn, only my smartphone

Last edited by Firestar (2022-08-31 07:47:37)

ewaller · 2022-08-31 05:33:50

First, please stop posting large pictures as in-line images. Use url tags to post a link to the photo as opposed to img tags. Second, please post the actual text, not a picture of it.

Leaving my moderator role, Does your wlan0 not have a 10.2.32.137/19 address? Note that the /19 means the first and second bytes will be 10.2. That accounts for 16 pits of the /19. That, along with the .32 in your address means bit 7 of the third byte is 0, pit 6 is 1 and bit 5 is 0. Bits 4,3,2,1,0 can take on any value, as can the endire 4th byte. In other words, The address (in binary) will be 00001010 00000010 001x xxxx xxxx where the x bits may take any value.

Arch Linux

#1 2022-08-22 16:53:09

Can connect to network, can run pacstrap and pacman, but cannot ping

#2 2022-08-22 17:06:24

Re: Can connect to network, can run pacstrap and pacman, but cannot ping

#3 2022-08-22 17:25:01

Re: Can connect to network, can run pacstrap and pacman, but cannot ping

#4 2022-08-23 00:39:36

Re: Can connect to network, can run pacstrap and pacman, but cannot ping

#5 2022-08-25 17:11:24

Re: Can connect to network, can run pacstrap and pacman, but cannot ping

#6 2022-08-29 16:29:13

Re: Can connect to network, can run pacstrap and pacman, but cannot ping

#7 2022-08-31 04:06:57

Re: Can connect to network, can run pacstrap and pacman, but cannot ping

#8 2022-08-31 05:33:50

Re: Can connect to network, can run pacstrap and pacman, but cannot ping

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