Configuration Example, Switching
Link State Tracking
Last week a friend called me and told me he was having serious problems with his network. A complete blade environment wasn’t able to communicate with the rest of the network. I asked what changed in the network and he told me that he had added a VLAN to a trunk allowed lists. Because he … Read More
Custom ringtones and SMS sounds on iPhone 3G
I received an iPhone 3G with a new cell phone contract. I started to play a little with it and noticed that there are only a few ringtones on the iPhone. Of course you can get more ringtones, but you have to get them through iTunes and pay for them, and that is not my … Read More
Another NVRAM broken?
On Monday I visited another customer who had problems saving the running configuration of a Cisco devices. The devices involved were a Cisco 2620 and a Cisco 2610XM router. Both routers weren’t able to save their running configuration. Both routers show the following error-message: startup-config file open failed (Bad file number) By both routers I … Read More
NVRAM corrupt or broken?
Today some of my colleagues and I “rebuild” an existing ESX with NetApp network. We change multiple VLAN’s and did a lot of reconfiguring. Unfortunately some other people were working on the power, so sometimes all equipment had to power down. After we did our job, we started testing the environment. All DMZ VM’s weren’t … Read More
Configuration Example, Routing
Policy NAT on Cisco router
A colleague of mine had to implement an IPSec VPN tunnel from a customer to a supplier. The customer has a Cisco router for connecting to the Internet, so nothing special. The router is already setup and in production. Configuring an extra IPSec VPN tunnel isn’t very hard, the most important part is the negotiation … Read More
Cisco ASA & ESX: strange ARP behavior
Last week I had a very strange problem with a Cisco ASA firewall. The firewall is configured with multiple interfaces, including a DMZ interface. There are multiple servers in the DMZ. These servers are physical and virtual servers. The virtual servers are VMware servers in a blade environment. I configured the feature ip verify reverse-path … Read More