johnnywho
Posts: 6
Joined: Sat Aug 17, 2019 4:21 pm

Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 5:14 pm

I'm having an ethernet connectivity problem on a freshly installed Raspbian Buster Lite (2019-07-10)

I'm able to find the rpi4 on the network, but ssh is slow to connect and feels very laggy when typing.
DNS doesn't work out of the box. After specifying it manually, rpi4 finds the servers, but the speed is terribly slow ~1kb/s and connection often gets interrupted.

I tried WiFi, which works well, but my intended setup requires an ethernet connection. I used different cables, checked settings on my router, restarted it, but problem still persisted.
I swapped the same system on a sd card into my older raspberry pi 3b+ and it works without any problem – full speed no lag.

I decided to ask for replacement unit, but the new one I've got has the same problem.
This leads me to the conclusion that it's an issue related to my router.
Since I can't replace it, and my older rpi3b+ works well in that setup, I'm hoping some on this forum could help me finding a workaround to this issue.
Last edited by johnnywho on Sat Aug 17, 2019 5:41 pm, edited 1 time in total.

User avatar
neilgl
Posts: 947
Joined: Sun Jan 26, 2014 8:36 pm
Location: Near Aston Martin factory

Re: Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 5:34 pm

What happens if you temporarily unplug the Ethernet cable from the 3b+ and put it into the pi4?

johnnywho
Posts: 6
Joined: Sat Aug 17, 2019 4:21 pm

Re: Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 5:44 pm

neilgl wrote:
Sat Aug 17, 2019 5:34 pm
What happens if you temporarily unplug the Ethernet cable from the 3b+ and put it into the pi4?

Hot-swapping the cables doesn't fix it. SSH still laggy, server names still not found.

What's worth noting is that I also tried static ip configurations which didn't help much as well.

trejan
Posts: 566
Joined: Tue Jul 02, 2019 2:28 pm

Re: Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 5:46 pm

What brand/model switch is it?

Run "ifconfig". Are the error counters for eth0 all zero?

johnnywho
Posts: 6
Joined: Sat Aug 17, 2019 4:21 pm

Re: Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 6:12 pm

It's a rather unknown docsis 3.0 modem/router Technicolor EPC3940 from my cable provider.

I tested static ip config, with manually entered `static domain_name_servers=` in `/etc/dhcpcd.conf`. Pings seem low, but I had to wait 20 seconds to see the first ping result:

Code: Select all

pi@raspberrypi:~ $ ping google.com
PING google.com (216.58.207.78) 56(84) bytes of data.
64 bytes from 216.58.207.78: icmp_seq=2 ttl=53 time=13.7 ms
[redacted]....
64 bytes from 216.58.207.78: icmp_seq=22 ttl=53 time=14.5 ms
^C
--- google.com ping statistics ---
22 packets transmitted, 9 received, 59.0909% packet loss, time 760ms
rtt min/avg/max/mdev = 13.690/14.929/18.509/1.335 ms

Next ping command I tried has failed with an error:

Code: Select all

pi@raspberrypi:~ $ ping google.com
ping: google.com: Temporary failure in name resolution

Although no RX/TX errors in the `ifconfig` output:

Code: Select all

pi@raspberrypi:~ $ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.67  netmask 255.255.255.0  broadcast 192.168.0.255
        inet6 fd51:42f8:caae:d92e::ff  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::230e:5e0e:48d:2718  prefixlen 64  scopeid 0x20<link>
        ether dc:a6:32:12:fa:29  txqueuelen 1000  (Ethernet)
        RX packets 1422  bytes 140621 (137.3 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1030  bytes 136602 (133.4 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

drgeoff
Posts: 9803
Joined: Wed Jan 25, 2012 6:39 pm

Re: Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 6:39 pm

Looks like you are losing lots of incoming packets. Repeat the ping test but to the IP of the router/modem.

johnnywho
Posts: 6
Joined: Sat Aug 17, 2019 4:21 pm

Re: Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 7:20 pm

You were right, it loses packets when pinging the router.

Code: Select all

 pi@raspberrypi:~ $ ping 192.168.0.1 -c 8
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_seq=1 ttl=64 time=1.27 ms
64 bytes from 192.168.0.1: icmp_seq=6 ttl=64 time=1.42 ms
64 bytes from 192.168.0.1: icmp_seq=7 ttl=64 time=0.814 ms

--- 192.168.0.1 ping statistics ---
8 packets transmitted, 3 received, 62.5% packet loss, time 236ms
rtt min/avg/max/mdev = 0.814/1.168/1.417/0.257 ms
I plan to test it with different router on a different network, but that won't solve my problem at all.
What could be the reason that rpi3b+ works fine but two rpi4 units, all tried with the same sd card, are not working on my network?

drgeoff
Posts: 9803
Joined: Wed Jan 25, 2012 6:39 pm

Re: Raspberry Pi 4 Ethernet Problem

Sat Aug 17, 2019 9:53 pm

Edit their dhcpcd.conf files to give each RPi a static address. Connect them together with an ethernet cable. (Crossover cable not required.) Do the ping tests. If not losing packets, time to look more closely at the router. If losing packets something up with the RPi4B.

cpunk
Posts: 85
Joined: Thu Jun 29, 2017 12:39 pm

Re: Raspberry Pi 4 Ethernet Problem

Mon Aug 19, 2019 12:55 pm

Wow, this is exactly like my situation (thread over here).

I have an "EPC3940ADL EuroDocsis 3.0 2-PORT Voice Gateway" acting as my router, and I experienced packet losses of approximately 40%.

Static IP didn't help. Disabling IPv6 didn't help. I presume the ethernet interfaces try to reach gigabit speed, but start losing packets / frames at that speed.

I temporarily switched to WiFi and disconnected from Ethernet to suppress the problem. Since WiFi is overcrowded here, I am intending to add a separate WiFi router/switch to my network today.

epoch1970
Posts: 3653
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: Raspberry Pi 4 Ethernet Problem

Mon Aug 19, 2019 1:42 pm

Looks like this is a Cisco device, rebranded by ISPs.
Found a user guide at random on the Internet, found nothing obvious.
(Seems to operate as modem router only, not a bridged modem.)
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

cpunk
Posts: 85
Joined: Thu Jun 29, 2017 12:39 pm

Re: Raspberry Pi 4 Ethernet Problem

Mon Aug 19, 2019 6:53 pm

Update: I put a TP-Link wireless router downstream of it ( with routing functionality disabled in the TP-Link, so essentially my TP-Link is a switch with antennas or an access point ). Raspberries started working fine, even ping -f loses no packets.

Seems to be a compatibility issue with these Cisco devices.

User avatar
HawaiianPi
Posts: 4583
Joined: Mon Apr 08, 2013 4:53 am
Location: Aloha, Oregon USA

Re: Raspberry Pi 4 Ethernet Problem

Mon Aug 19, 2019 7:07 pm

You should see if it's possible to set the ISP supplied modem/router gateway into bridge mode, then connect a better router.

A few years ago I was in a rental with an ISP supplied gateway that was crap. Their tech support said it wasn't possible to set their router/modem device into bridge mode, but after some searching I found it was possible. After setting the ISP gateway to bridge mode and connecting my own router, it got an external IP and everything worked great.

Or check with the ISP to see if they have a modem only device with an Ethernet jack (my old cable TV ISP had modems without routers).
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?

johnnywho
Posts: 6
Joined: Sat Aug 17, 2019 4:21 pm

Re: Raspberry Pi 4 Ethernet Problem

Fri Aug 23, 2019 2:22 pm

The problem turned out to be compatibility issue between rpi4 and my ISP branded Cisco router.

I connected my rpi4 to another network with a gigabit switch and immediately noticed an improvement during connecting and typing commands over ssh. No ping packet losses and decent internet speeds when using speedtest-cli. I connected an external usb3 hdd and tried transferring files over smb (~35MBytes/s) and sftp (~40MBytes/s). Not a gigabit-speed, but still an usb3 upgrade that I wanted to achieve.

I know that with a bit of hack I can trick my router into bridge mode and put a new router behind it, but that's rather a workaround to my problem. I will try to persuade my ISP to let me use a third-party modem/router which I was planning to buy for some time now (my current EPC3940 drops wifi speed over short range).

It's still a bit disappointing since this is not a purely hardware problem. After all, rpi3b+ works perfectly all this time, which leaves the only possibility that rpi4 uses different mode or parameters that cause the incompatibility. I strongly believe there should be a way to change them on the rpi4 itself without the need of the new hardware.

If someone has any suggestions what config options can potentially work as a fix, please post it here, I'll be glad to try it out.

Anyways, thanks guys for all your help so far.

sniegu.pl
Posts: 2
Joined: Sun Sep 15, 2019 11:15 am

Re: Raspberry Pi 4 Ethernet Problem

Sun Sep 15, 2019 11:33 am

Hi,

You can force the connection to be 100Mbps instead of 1Gbps as a workaround. It's handicap but IMHO better than switching to wifi and fighting for radio resources with other devices in the network.

Code: Select all

# ethtool -s eth0 speed 100 duplex full

hiox
Posts: 1
Joined: Sun Sep 15, 2019 8:53 pm

Re: Raspberry Pi 4 Ethernet Problem

Sun Sep 15, 2019 9:00 pm

Hi there!

I've noticed the same problem. I have Cisco router and ssh connection to my Pi4 4gb over Ethernet Is extremely slow and lagging. Once wifi was setup everything works nice. Is there any solution to this?

Thanks!

Mike_333
Posts: 1
Joined: Tue Sep 17, 2019 2:41 pm

Re: Raspberry Pi 4 Ethernet Problem

Tue Sep 17, 2019 2:46 pm

Same thing, upc connect box (compal ch7465lg), when enabled 1000mb - lost packets, when enabled 100mb - all is good
temporary solution enable 100mb at startup:

crontab -e

add
@reboot sleep 10 ; /sbin/ethtool -s eth0 speed 100 duplex full

Return to “Troubleshooting”