After a frustrating morning testing several different updated firmwares, I’ve determined that NAT (Network Address Translation) loopback is broken on firmwares 184.108.40.206 and 220.127.116.11 for the Draytek Vigor 2820VN. Other routers in the family are likely to be similarly affected.
Another post in a series designed to help Future-Howard work out why things have broken.
If you install Java 6 Update 13 and then try and log into Cisco SDM 2.5 it will fail. The SDM console will not load.
With that the Cisco SDM started working again. I’ve not found anything about this on the Cisco site.
In my last post, you discovered my obsession for generating statistics on my network usage and my use of MRTG to draw pretty little graphs. Writing that post got me thinking about my Counter-Strike server, and what data I could usefully graph from it. A bit of Googling led me to this page where a Dutch guy had used MRTG to graph the number of users and the network frames per second of his CS:S server – running on Ubuntu Linux.
The image on the left is just one of the graphs generated automatically for tracking the data usage on my home network.
That particular graph shows the usage of my ADSL connection over time; green is downloaded data, while the blue line shows my uploads. It is generated by Tobi Oetiker’s outstanding MRTG – The Multi Router Traffic Grapher. MRTG is a free Perl script that connects to any device capable of talking SNMP and pulls interesting data from it.
I currently log DSL, Wireless and LAN use (Bytes per second), along with line noise and Noise Margin of the DSL connection. I could also log what the switch in my network is doing, and even what my various servers are up to. As you can see from the graphs you get a nice indication of traffic patterns over time – it’s very easy to spot peaks when BitTorrent kicks in and out, or when someone in a different time zone is playing on my Counter Strike server!
It gives me an “at a glance” overview of what most of my networked devices are doing – which was enough to make me notice the other day that despite having all my wireless devices switched off, something was still polling the Access Point. Turns out I’d left one of the laptops disassociated – but on – and it was sending a little chatter to the AP every few hours.
I keep needing to do this – so once again to help my future self:
When you have a number of public IPs being translated through a router to an internal address space, a router’s dynamic translation can get full. I’ve got an 877W, and it seems that a combination of running BitTorrent and a CounterStrike: Source server can quickly cripple the router (even with a memory upgrade!). When it gets too full you end up getting timeouts on other connections, usually this is most obvious by my browser failing to return pages.
To clear the dynamic translation table before timeout occurs log in to the router via ssh (or telnet) and in enable mode, type:
clear ip nat translation *
That seems to do the trick on my network anyway.