Category: Switching
What is an UPLINK port?
A colleague recently encountered some problems with keepalives on switch ports. He wrote a post about it. Keepalives are, quoted from his blog post: By default Cisco routers and switches periodically test their (Fast) Ethernet links by sending out Loopback frames (ethertype 0×9000) addressed to themselves. Call it a “L2 self-ping” if you will. In … Read More
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
Configuration Example, Routing, Security, Switching
Secure HSRP configuration
A friend of mine works for a well known auditing and penetration testing company in the Netherlands. Recently we were talking about how he starts looking for flaws in network infrastructures. My friend told me that the first thing he does is simply starting WireShark and start looking at all the packets he receives. By … Read More
IBM Blade with Nortel and HP switches
Today I had to troubleshoot an IBM Blade system. The customer was complaining that all servers, except one, weren’t able to communicate with the rest of the network. The blade system contains two Nortel switches. Each Nortel switch is connected with a 3 Gbps LACP channel to separate HP switches. The HP switches are the … Read More
Configuration Example, Security, Switching
Layer 2 security
I attended the session layer 2 security, because I had some discussions about layer 2 security with one of my colleagues. We were discussing about using layer 2 security and especially implementing it in the environments from our customers. Looking at my/our customers, I don’t see environments where layer 2 threats would be immediate. But … Read More
HP Blade Switch Development
Maybe old news for some of you, but HP has developed the Cisco switches for the HP Blade servers. The Cisco Catalyst Blade Switch 3120G and 3120X provide stacking functionality. This improves the functionality of the switches by creating a single switch from two physical switches. Source: The Cisco Catalyst Blade Switch 3120 Series Switches … Read More