Router mode doesn't give internet access to connected devices

Drightiger · 2023-10-01T20:28:32.545Z

AX1800 Router

I’m in a weird setup, I feel on the surface this should be simple but it isn’t having it.

Router connected to a university-style WAN that allows devices via their MAC address’, only a limited number of devices/MAC address’ allowed and even fewer MAC address changes during each billing period. Each room has a 1Gbps port running to it. I’ve bought the AX1800 with the idea of only using the router’s MAC address and only 1 MAC address – hopefully this isn’t wrong? The company charges extra for each device you want to add.

Connected up the router to the WAN, authorised the routers MAC address on my accounts whitelist, router has internet connection as it downloaded an update, but it can’t bridge the other connected devices onto it? What am I missing?

wcs2228 · 2023-10-02T03:12:04.926Z

The university may be detecting that you are using a router, which defeats their restriction to a limited number of devices/MAC addresses (and additional payment to them for more devices).

A common method they use is to check the TTL in the packets, which you may be able to bypass:

Changing TTL in OpenWrt 22.03 Technical Support for Routers

As OpenWrt 22.03 uses nftables to replace iptables, the original ttl command is not working. Here is how to change ttl for all outgoing interfaces to 65. SSH to the router and use the following mkdir -p /usr/share/nftables.d/chain-pre/mangle_postrouting/ echo "ip ttl set 65" > /usr/share/nftables.d/chain-pre/mangle_postrouting/01-set-tt l.nft fw4 reload

Be aware that they may terminate your service if they can detect that you are trying to cheat them.

I do not work for and I am not directly associated with GL.iNet

Drightiger · 2023-10-02T19:32:15.788Z

Thank you for helping.

I had to change the fw4 to fw3 before the reload command works, however when I ping the localhost it stays ttl = 64 and not 65 as that thread should suggest.

I’m assuming this works by the ttl of the packets sent by the router to the higher router used by the company should read 63, and when they read 62 it knows a routers involved, and I’m setting 65 to add 1 for when packets reach the companies higher router?

Any suggestions?

Thanks in advance

wcs2228 · 2023-10-03T01:27:17.625Z

The post that I linked is for Firmware 4, so it should have worked.

You can try the following method for Firmware 3:

Change outgoing TTL Technical Support for Routers

Hi all, Cool little router. Having a couple issues though that I hope someone could help with. I have been messing with the firewall rules to change the outgoing TTL to 65, but I can’t seem to get it to work. Looking at the packages installed, everything is there for mangle and Postrouting… So I am a bit lost… I have tried: iptables -t mangle -A POSTROUTING -j TTL --ttl-set 65 and iptables -t mangle -I POSTROUTING -o get_wanface -j TTL --ttl-set 65 but no luck. Edit: figured out the ssh i…

Drightiger · 2023-10-03T16:14:28.611Z

You sent me down the right rabbit hole and I got this working via someone’s more recent comment recent in that thread.

My flint is still fw3 and not 4 (don’t know why, don’t care). Changing ttl in a postrouting command didn’t work, but changing the pre-routing did:

iptables -t mangle -I PREROUTING 1 -j TTL --ttl-set 65

Thank you so much.