IP Routing from Subnet to Gateway

Asked by Daniel McLane

The system runs Ubuntu 16.04 LTS. It has a WAN port using a modem, and the LAN has ethernet and wlan interfaces. The problem is that WLAN clients (192.168.1.0/24) can ping internet hosts using either name or IP address, but a WLAN client cannot browse the internet. Ethernet (192.168.0.104) and local clients can browse the internet. IP forwarding is on.

The WLAN is on 192.168.1.0/24 and the ethernet is 192.168.0.1. The problem does not seem to be a DNS problem because the ping by host name is working.

As a test, we set up a simple HTTP test site on a remote machine and were able to browse to it on the WLAN. So strangely it seems that small data transfers work, but more complex sites fail. This tends to show that the routes and policies are OK. (Details follow).

Not sure this matters but this is an ARM platform. The kernel is 4.1.4.

Any insight is much appreciated.

Interfaces:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
    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
2: can0: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10
    link/can
3: can1: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10
    link/can
4: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 10:0d:32:00:ea:e6 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.104/24 brd 192.168.0.255 scope global eth0
       valid_lft forever preferred_lft forever
5: wlp4s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 20:16:d8:0a:c7:86 brd ff:ff:ff:ff:ff:ff
6: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0e:8e:55:e2:23 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.1/24 brd 192.168.1.255 scope global wlp3s0
       valid_lft forever preferred_lft forever
7: wwan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1430 qdisc pfifo_fast state UNKNOWN group default qlen 1000
    link/ether XX:XX:XX:d3:ae:c4 brd ff:ff:ff:ff:ff:ff
    inet 30.XXX.XXX.222/30 brd 30.XXX.XXX.223 scope global wwan0
       valid_lft forever preferred_lft forever
112: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 100
    link/none
    inet 10.8.0.201 peer 10.8.0.1/32 scope global tun0
       valid_lft forever preferred_lft forever

IP Tables
# Generated by iptables-save v1.6.0 on Fri Jun 2 15:24:14 2017
*nat
:PREROUTING ACCEPT [17018:2008635]
:INPUT ACCEPT [9833:1399535]
:OUTPUT ACCEPT [3684:262964]
:POSTROUTING ACCEPT [3680:262076]
-A POSTROUTING -s 192.168.1.0/24 ! -d 192.168.1.0/24 -j MASQUERADE
COMMIT
# Completed on Fri Jun 2 15:24:14 2017
# Generated by iptables-save v1.6.0 on Fri Jun 2 15:24:14 2017
*filter
:INPUT ACCEPT [85675:51658650]
:FORWARD ACCEPT [1381746:556269585]
:OUTPUT ACCEPT [70009:9356900]
COMMIT
# Completed on Fri Jun 2 15:24:14 2017

IP Routes
default via 30.XXX.XXX.221 dev wwan0
10.8.0.1 dev tun0 proto kernel scope link src 10.8.0.201
30.XXX.XXXX.220/30 dev wwan0 proto kernel scope link src 30.XXX.XXX.222
192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.104
192.168.1.0/24 dev wlp3s0 proto kernel scope link src 192.168.1.1

IP Forwarding
/proc/sys/net/ipv4/ip_forward = 1

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