Can't access DSL modem in bridge mode

tombadog · March 10, 2021, 10:26am

Also having some issues accessing my Technicolor Modem (ADSL) which is in bridge mode. I have followed this guide (https://openwrt.org/docs/guide-user/network/wan/access.modem.through.nat). But after banging my head against the table to see what I may have done wrong, I still can't work it out. I'm not even able to ping the modem. Modem and Openwrt router are in different subnets but no success.

frollic · March 10, 2021, 10:30am

are you sure there's anything to access, once the device's in bridge mode ?

tombadog · March 10, 2021, 10:33am

Yes. The modem still allows you to connect directly (either wired or wireless) and login to the web interface.

frollic · March 10, 2021, 11:23am

.... and what IP is it responding at ?

tombadog · March 10, 2021, 11:26am

Responding at 192.168.1.1 (Openwrt router is 192.168.10.1)

vgaetera · March 10, 2021, 12:28pm

Collect the diagnostics and post it to pastebin.com redacting the private parts:

uci show network; uci show firewall; \
ip address show; ip route show table all; ip rule show; iptables-save

tombadog · March 10, 2021, 12:56pm

vgaetera · March 10, 2021, 3:17pm

Try to ping the modem from OpenWrt.
If the issue persists, try to power-off the modem, wait a minute, power-on it again.
If there's still no success, try to analyze the traffic:

# OpenWrt
opkg update
opkg install tcpdump
tcpdump -evni any host 192.168.1.1

# Client
ping 192.168.1.1

moeller0 · March 10, 2021, 3:32pm

If you are on PPPoE/PPPoA maybe the instruction that reads:

Interface: @wan
might be off? Try to select the appropriate ethernet interface say, eth1 or so instead?

tombadog · March 10, 2021, 3:39pm

I've selected eth1.2 (wan,wan6). I'm guessing this is correct?

tombadog · March 10, 2021, 3:39pm

tcpdump: listening on any, link-type LINUX_SLL (Linux cooked v1), capture size 262144 bytes
15:34:00.132075  In 2c:fd:a1:ce:73:3f ethertype 802.1Q (0x8100), length 80: vlan 1, p 0, ethertype IPv4, (tos 0x0, ttl 128, id 25569, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 34, length 40
15:34:00.132075  In 2c:fd:a1:ce:73:3f ethertype IPv4 (0x0800), length 76: (tos 0x0, ttl 128, id 25569, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 34, length 40
15:34:00.132075  In 2c:fd:a1:ce:73:3f ethertype IPv4 (0x0800), length 76: (tos 0x0, ttl 128, id 25569, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 34, length 40
15:34:00.132107 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:01.169051 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:02.209050 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:03.251720  In 2c:fd:a1:ce:73:3f ethertype 802.1Q (0x8100), length 80: vlan 1, p 0, ethertype IPv4, (tos 0x0, ttl 128, id 25570, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 35, length 40
15:34:03.251720  In 2c:fd:a1:ce:73:3f ethertype IPv4 (0x0800), length 76: (tos 0x0, ttl 128, id 25570, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 35, length 40
15:34:03.251720  In 2c:fd:a1:ce:73:3f ethertype IPv4 (0x0800), length 76: (tos 0x0, ttl 128, id 25570, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 35, length 40
15:34:03.251745 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:04.289050 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:05.329054 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:06.381947  In 2c:fd:a1:ce:73:3f ethertype 802.1Q (0x8100), length 80: vlan 1, p 0, ethertype IPv4, (tos 0x0, ttl 128, id 25571, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 36, length 40
15:34:06.381947  In 2c:fd:a1:ce:73:3f ethertype IPv4 (0x0800), length 76: (tos 0x0, ttl 128, id 25571, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 36, length 40
15:34:06.381947  In 2c:fd:a1:ce:73:3f ethertype IPv4 (0x0800), length 76: (tos 0x0, ttl 128, id 25571, offset 0, flags [none], proto ICMP (1), length 60)
    192.168.10.109 > 192.168.1.1: ICMP echo request, id 1, seq 36, length 40
15:34:06.381974 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:07.409049 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
15:34:08.449053 Out 60:38:e0:c7:53:68 ethertype ARP (0x0806), length 44: Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.1 tell 192.168.1.2, length 28
^C
18 packets captured
27 packets received by filter
0 packets dropped by kernel

trendy · March 10, 2021, 3:57pm

The modem is not responding to arp requests from the OpenWrt, so no communication is possible.
Have you tried to connect a PC on the modem with configured IP 192.168.1.2/24 and test the modem?

tombadog · March 10, 2021, 4:05pm

I can connect my phone configured as 192.168.1.2/24 over its WiFi (which I've temporarily turned on)

trendy · March 10, 2021, 4:09pm

That's fine, but you need to try the ethernet port.

tombadog · March 10, 2021, 4:10pm

Will do when possible (other users relying on internet at the moment).

tombadog · March 10, 2021, 8:13pm

Seems like something's not working on the modem. Even though the router is connected and working fine when plugged into it, it isn't showing as detected on the modem. According to the modem, all it's 4 Ethernet ports are unused (same if a pc is plugged in). Maybe a factory reset?

danijeltudek · March 10, 2021, 8:39pm

Then it's possible that the bridge mode on Technicolor removes ethernet ports from LAN group and bridges them all to DSL connection.
I remember that Speedtouch/Technicolor devices are highly configurable through command line so maybe you could work around that somehow but I can't tell you what exactly you should do.
I'd start with searching for instructions on how to put the old ST780 in bridge mode and try modifying that.

tombadog · March 10, 2021, 9:05pm

Apart from port 4 it looks like, after reading this guide form Zen (https://support.zen.co.uk/kb/Knowledgebase/Technicolor-TG589vac-Bridge-Mode). Not sure this really helps me though.

trendy · March 10, 2021, 9:13pm

I remember some modem/routers when switched to bridge mode could no longer be managed. Only way to manage them again was to factory reset by pressing the reset button. Maybe this modem is like them.

tombadog · March 11, 2021, 7:35am

It looks like it's accessible for management on LAN 4 (&wireless) but not LAN 1-3 which is which is where the Openwrt router must be plugged in. Looks like it isn't possible (at least withing my capabilities).