Fiber optics and UDLD
UDLD (Unidirectional Link Detection) is a protocol to help prevent forwarding loops in switched networks. A fiber cable is build from two separate fibers (transmit and receive), where one of the two fiber could fail, which would result in a switch port not able to receive or send traffic. This scenario could result in some … Read More
Failed to establish VPN through PIX
We migrated our Internet connection lately and reconfigured our PIX firewall. We added some memory to install the latest firmware version (8.0(4)). After putting the PIX firewall in production some of the employees were complaining they couldn’t establish any PPTP VPN Tunnels anymore to customers. Every time when some one called me, I tried it … Read More
Tools Page updated
I added a new tool to the Tools page, called Interface Traffic Indicator. The tool can be compared to STG, but needs to be installed on a workstation. The tool can be used to measure the throughput of a specific interface. To use the tool, you need at least the IP address of the device … Read More
Configuration Example, Routing
HSRP and ACL’s
I added a Guest VLAN to a network environment with two multi layer switches running HSRP. To secure the internal network from the Guest VLAN, I added a ACL to the Guest VLAN SVI. The ACL is stated below: ip access-list extended GUEST-DENY-RFC1918 remark Allow DHCP permit udp any eq bootpc any remark Deny RFC … Read More
Fully Automated Nagios
A colleague noticed the new developments regarding Nagios. Nagios is an Open Source host, service and network monitoring program. I always had my doubts about Nagios, especially about the manageability of the application. The installation and configuration of Nagios can be very time consuming. And a lot of customers are “afraid” of using Nagios, because … Read More
Cisco.com Searches and Tools
Cisco published some tool and search plugins to your Internet Explorer 7 and Firefox 2/Firefox 3 browser. This makes it possible to quickly search the Cisco.com website for a particular question or item. Check the following website for more information: http://www.cisco.com/web/tsweb/searchplugins/plugin_homepage.html#