OTish Weird network behaviour

[leen...]

Hi All,

I got a few second hand routers and set them up around the house to extend the WiFi coverage. I have a central network "server" which runs the DHCP server, firewall etc etc. so on these routers have switched of DHCP and set them to have static IP addresses. They all work fine except for 1 which is a BT Smart Hub (only one of this type). The issue is that when I connect to it via WiFi I don't get an IP address even though the laptop shows it has connected to it ok. If I connect the laptop to the same router with an Ethernet cable it works fine.

I am running Ubuntu and here are the outputs of "ifconfig"

When connected by Ethernet cable only

enp0s25: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.1.190 netmask 255.255.255.0 broadcast 192.168.1.255 inet6 fdaa:bbcc:ddee:0:f086:e7ed:575a:cf22 prefixlen 64 scopeid 0x0<global>

inet6 fdaa:bbcc:ddee:0:71ab:8e32:aadb:423b prefixlen 64 scopeid 0x0<global>

inet6 fe80::2b80:b2bf:56e:e4da prefixlen 64 scopeid 0x20<link>

ether 68:f7:28:19:ea:6b txqueuelen 1000 (Ethernet) RX packets 524 bytes 98442 (98.4 KB) RX errors 0 dropped 13 overruns 0 frame 0 TX packets 350 bytes 66873 (66.8 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf0600000-f0620000

When connected by WiFi only

enp0s25: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 ether 68:f7:28:19:ea:6b txqueuelen 1000 (Ethernet) RX packets 8508 bytes 6727440 (6.7 MB) RX errors 0 dropped 43 overruns 0 frame 0 TX packets 3567 bytes 823306 (823.3 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf0600000-f0620000

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10<host>

loop txqueuelen 1000 (Local Loopback) RX packets 995 bytes 139451 (139.4 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 995 bytes 139451 (139.4 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet6 fdaa:bbcc:ddee:0:ed6f:210e:bdef:4c37 prefixlen 64 scopeid 0x0<global>

inet6 fe80::5bdc:3cee:8de2:2469 prefixlen 64 scopeid 0x20<link>

inet6 fdaa:bbcc:ddee:0:351d:2ed9:ec6f:1527 prefixlen 64 scopeid 0x0<global>

ether e8:b1:fc:60:6c:33 txqueuelen 1000 (Ethernet) RX packets 2153 bytes 1757300 (1.7 MB) RX errors 0 dropped 12 overruns 0 frame 0 TX packets 1298 bytes 230487 (230.4 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

I assume inet6 is the IPv6 address so it is almost as if for some reason I am not being given an IPv4 address? I wondered if the router was intercepting the DHCP request and giving an IPv6 address (must say don't know much about IPv6)? The config to switch off DHCP server on the router is in the IPv4 tab.

Only other relevant info is that this is not an issue with the laptop as none of the mobile phones will connect either waiting on "getting IP address".

Any help gratefully appreciated.

Thanks

Lee.

[Theo]

Those IPv6 addresses are local and link-local only, ie you don't have IPv6 connectivity they're just generated locally. You haven't received a public IPv6 address so you can't talk to the IPv6 internet (unless the router is doing v6 NAT, which is unusual).

It sounds like your link is up (packets are going past) so your WPA key/etc are ok, but you aren't getting DHCP traffic. I would try running wireshark or similar on wlp3s0 and watching what happens - does your machine make a DHCP v4 request? Is there an answer?

One thing I have had problems with the BT Smart Hub with is it doesn't like a machine roaming from ethernet to wifi and back again: I put a second WAP on one of the ethernet ports, but the router couldn't cope with a device connecting to the internal wifi, and then dropping off and reconnecting to what it saw as ethernet (via the WAP). I don't think you would run into that problem because you're connecting with different interfaces (ethernet and wifi of your machine have different MAC addresses so the smart hub sees them as different machines).

ISTR another similar problem publicised for the smart hub, but by then I'd stopped using it and don't remember the details. I think a firmware update was released to fix whatever it was, so maybe worth checking that is up to date (the BT forum has various threads on issues with different firmware).

Theo

[leen...]

Thanks Theo. I installed wireshark and it looks like the DHCP request is sent but no response. If I connect the laptop to a different router I can see the dhcp request go out and then the response with IP address come back. Seems like the smart hub is somehow filtering the dhcp traffic :(

[David Wade]

BT Smarthubs are not "Smart". The expect to be the only hub. Its worth checking to see if it can be re-flashed. Some can have openwrt installed

Dave

[John Walliker]

It would be worth checking that your ethernet connection is plugged into a LAN port, not a WAN port on the Smarthub. Smarthubs vary, but some have a WAN port intended to connect to a separate fibre modem. If you use this the firewall and NATing will block DHCP. There are also some WIFi routers around that prevent wirelessly connected devices from seeing devices connected by wired ethernet. Last time I came across one of these I tried to disable this "feature" but failed.

John

[leen...]

Looks like the router has a very old firmware SG4B1000B540 it says Jan 1 2001 but assume that is because it was factory reset. Looking online it seems the only way to update it is for it to come from BT but not sure now how/ whether BT will push a new update to it. Given it seems to work when I connect the laptop via Ethernet cable, I assume it does have internet connectivity to get the update but it could of course be wired to get it through the broadband link only?

Also tried mucking around with the various config settings including disabling the firewall but no joy. There is a setting on the DHCP called "Authoritative DHCP" I swear when I turned that on but DHCP off I got it to work (no idea why) but don't seem to be able to recreate it.

[Theo]

The original Smart Hub can, but most things like DSL and wifi don't work - makes it not very useful. There aren't drivers for the relevant Broadcom hardware.

I don't think the Smart Hub 2 is any better.

(The previous versions, in particular the HomeHub 5a, were much more useful)

Theo

[Tim+]

Ditch the lot and invest in a mesh system. Best thing we ever did.

Like you I had repurposed old routers as hot spots and we had other Wi-Fi repeaters but the lack of seamless roaming between hotspots was a real pain.

Tim

[The Natural Philosopher]

Most likely its not working in bridge mode.