Side Effects with WAN DHCP Failure

[jimf]

This evening my cable modem somehow got hosed up and the router was reporting an inability to obtain DHCP from my ISP. Rebooting the cable modem fixed it, but noted these side effects that shouldn't have anything to do with the WAN (or LAN for that matter) DHCP.

1. Couldn't access my cable modem's IP address via web browser. This is a different subnet, but I'd think it would just route to the WAN side.

2. Wireless hosed. Couldn't get to the router via web interface. Wired connection was fine.

3. Couldn't get to other computers on the same subnet via WINS. The router is the WINS server, but I wouldn't think that would be affected by a WAN outage.

Running 380.68 on AC68R.

Anyone else had a similar issue? This is pretty minor since it looks like the cable modem tried to renew it's DHCP lease which, thankfully, doesn't happen too often. No other errors found in router or modem logs. This may be the reason for #1 as the cable modem may have stopped responding.

Merlin,
Thanks for another great release!

 

[JDB]

1. If the router has no WAN IP it can't route to any subnet on that side (same subnet or otherwise). Unless you've added a second static IP to the WAN interface (I have for this reason)?

2. If you were going to the LAN IP of the router that's odd. If you were trying to use router.asus.com or the local domain name of the router then no WAN DNS will be the reason.

3. Agree this shouldn't be affected, but as above, maybe lack of WAN DNS does something odd to the router's WINS/DNS overall


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[jimf]

JDB, thanks. How does one add a second IP to the WAN? That would be nice just to query the cable modem in those situations. For #2, yes I was using the router's LAN IP.

 

[Vexira]

Try Mac clone the cable modem

 

[JDB]

If you ssh to the router and create the file /jffs/scripts/services-start

And add the contents as something like mine;

ifconfig eth0:1 10.11.20.254 netmask 255.255.255.0
iptables -t nat -I POSTROUTING ! -s $(nvram get lan_ipaddr) -d 10.11.20.0/24 -j SNAT --to 10.11.20.254
logger Set routing to BT Openreach Modem


My modem has a management IP of 10.11.20.1 and the Asus gets an IP of 10.11.20.254. I've set it so I could have other devices in the whole /24 subnet alongside the modem. If you want it specifically for the 1 management IP of your modem, change the 10.11.20.0/24 to <your_modem_ip>/32. Really you should update the netmask in this case too, but without know what ip/netmask your modem has I can't suggest what to.
The logger is just a comfort thing so from the GUI in the log at boot you'll see it's executed the script.

Hope it helps!


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