Posts Tagged ‘network’

Accessing status and diagnostic information for a Motorola Surfboard cable modem

Wednesday, May 28th, 2014

My ISP (to protect its identity, let’s call it Flomflast) drops my internet connection frequently. During the latest occurrence, I noticed from my router’s status page that the WAN address had been assigned to 192.168.100.11. I was surprised to see this since I believed there was no connection to the ISP via the cable line. How could the ISP DHCP server assigned an ip address to the router? And why the private network address?

I guessed that if the DHCP server was assigning addresses in the 192.168.100.x range then itself or another server (the gateway?) might be located at 192.168.100.1. I typed the address in the address bar of my favorite web browser and was greeted with a web page being served by my Motorola Surfboard cable modem.

Screenshot - 05282014 - 11:14:33 PM

On the configuration page I found information that the cable modem has a built-in DHCP server that takes over when the internet connection is dropped. As configured, it begins assigning addresses at 192.168.100.11. Since my router is the only device on that side of the network with the cable modem, it was assigned the first ip address in the range.

The status page for the cable modem is especially handy. From the comfort of my chair I can see that the internet connection is indeed lost without the usual process of several rounds of pinging followed by a walk to another room to check the modem lights. Even with the internet connected, the modem is still accessible at 192.168.100.1.

How to fix slow DNS look-up’s in Firefox running under Linux

Sunday, July 21st, 2013

I’ve had this problem for some time now and chose today to do some research. Luckily, I found a workaround pretty quickly.

I use the Mozilla based browser GNU IceCat which is functionally equivalent to Mozilla Firefox. When a page is requested, the browser displays a small spinning icon in the left corner of the tab. Loading a page involves three basic steps: converting the URL into an IP address, contacting the web server at the IP address, receiving the web page (and other resources). During the first two steps, the icon will be grey and spinning counter-clockwise. The status bar will show messages like “Looking up google.com” and “Waiting for google.com”. Typically, DNS queries (the first step) take on the order of 100 ms to complete. Therefore if you see the first message, you may have the same problem.

The symptom was that IceCat (Firefox) was taking about 3 to 5 seconds to make DNS queries every time I tried to navigate to a new address. The cause of the problem seems to be that my system is making IPv6 DNS queries first by default but these types of requests are being ignored by the DNS resolver which doesn’t support IPv6. My system sends a query and then waits a certain amount of time before giving up and trying an IPv4 query. That time waiting was the delay I was experiencing.

The ideal fix would be to change the way the DNS resolver responds to IPv6 DNS queries. That’s obviously out of my control. A system-wide fix involves setting up your own DNS resolver – a bit more work than I’m interested in. The easy fix was to address the issue for IceCat (Firefox) only which is good enough for me as web-browsing is my primary internet activity.

The fix is to change the value for the key “network.dns.disableIPv6″ from “false” to “true” in IceCat’s (Firefox’s) “about:config” page.

For more information, the issue has been discussed extensively here:

https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/417757