This is a nasty little issue. On my private network, suddenly some endpoints would refuse to establish calls made over SIP or H323. Error codes would be:

channel unacceptable
487 / Request Terminated
480 / Temporarily Not Available

Not particularly helpful information. After all the packet sniffing and diagnostic checks, it appeared …

1. Create your openDNS.com account. Add your Network to their system, etc.

2. Go to the "System" -> "General setup" page.

3. Set the DNS address to the OpenDNS':

   208.67.222.222
   208.67.220.220
   

Now just make sure that "Allow DNS server list to be overridden by DHCP/PPP on …

We got some Procurve 2810 Gigabit switches. they play some critical roles, so I wanted to keep others from playing with them. The exact code below would enable https for web management, enable ssh for console management, change the port ssh runs on, and disable telnet and unencrypted web management …

Install package ifenslave-2.6.

apt-get install ifenslave

make sure the real NICs kernel modules are loaded automatically

modprobe --list | grep -i bonding

edit /etc/network/interfaces to look like this:

auto bond0
iface bond0 inet static
address 192.168.1.59
netmask 255.255.255.0
gateway 192.168.1 …