Category Archives: Networking

HPE Networking expert level certifications

A couple of days ago, I took the HP0-Y47 exam “Deploying HP FlexNetwork Core Technologies”. It was one of two required exams to achive the HPE ASE – Data Center Network Integrator V1, and the HP ASE – FlexNetwork Integrator V1 certification. It was a long planned upgrade to my HP ATP certification, and it is a necessary certification for the HPE partner status of my employer.

You might find it confusing that I’m talking about an HP ASE and a HPE ASE. That is not a typo. The HP ASE was released prior the HP/ HPE split. The HPE ASE was released after the split in HP and HPE. read more

vSphere Distributed Switch health check fails on HPE Comware switches

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During the replacement of some VMware ESXi hosts at a customer, I discovered a recurrent failure of the vSphere Distributed Switch health checks. A VLAN and MTU mismatch was reported. On the physical side, the ESXi hosts were connected to two HPE 5820 switches, that were configured as an IRF stack. Inside the VMware bubble, the hosts were sharing a vSphere Distributed Switch.

The switch ports of the old ESXi hosts were configured as Hybrid ports. The switch ports of the new hosts were configured as Trunk ports, to streamline the switch and port configuration. read more

Demystifying “Interfaces on which heartbeats are not seen”

By accident, I found a heartbeat/ VLAN issue on a NetScaler cluster at one of my customers. The NetScaler ADC appliances have three interfaces connected to a switch stack. Two of the three interfaces were configured as a channel (LAG). This is a snippet from the config:

On the switch stack, the port to which interface 1/3 is connected, is configured as an access port. The ports, to which the channel is connected, is configured as a trunk port with some permitted VLANs. The customer is using HPE Comware based switches. The terminology is the same for Cisco. If you use HPE ProVision or Alcatel Lucent Enterprise, translate “access” to “untagged” and “trunk” to “tagged”. Because the channel is configured as a trunk port on the switch, the tagall option was set. read more

Citrix Certified Professional – Networking (CCP-N) exam experience

Last friday I passed the 1Y0-351 (Citrix NetScaler 10.5 Essentails and Networking) exam with a pretty good score. The exam was necessary, not only because I will do much more NetScaler projects in the future, but also because Citrix has made it mandatory to have a CCP-N in your company to to sell Citrix NetScaler.


My employer booked me a 5-day course (CNS-220 Citrix NetScaler Essentials and Traffic Management). Very nice, although I already had experience with NetScaler deployments. This training was designed for NetScaler 12.0, not for 10.5. read more

Notes about 802.1x and MAC authentication

Open network ports in offices, waiting rooms and entrance halls make me curious. Sometimes I  want to plugin a network cable, just to see if I get an IP address. I know many companies that does not care about network access control. Anybody can plugin any device to the network. When talking with customers about network access control, or port security, I often hear their complains about complexity. It’s too complex to implement, to hard to administrate. But it is not sooo complex. In the easiest setup (with mac authentication), you need a switch, that can act as authenticator, and a authentication server. But IEEE 802.1x is not much more complicated. read more

NetScaler ADC – Hidden vServer for HTTPS redirect

Starting with release 11.1, NetScaler ADC offers an easy way to redirect traffic from HTTP to HTTPS within the configuration of a load-balanced vServer. With 11.1, Citrix introduced the paramter  -redirectFromPort and -redirectURL.

While playing with a NetScaler ADC in my lab, I discovered a strange error message as I tried to configure the redirect.

Internal vserver couldn’t be set?! Okay, there was already a vServer, that was listening on port 80. After removing the vServer, I was able to setup the redirection and it was working as expected. read more

Enable IPv6 SLAAC on HPE OfficeConnect 1920 switches

The HPE OfficeConnect 1920 switch series is designed for SMBs. The switch is perfect for small environments, that require features like VLANs, routing or 802.1x. This switch is smart-managed, so it has “only” a web interface and only a limited CLI.

I have two switches in my lab: A 1910-8G and the successor, a 1920-24G. Although the device supports IPv6, it doesn’t support SLAAC (Stateless Address Autoconfiguration) by default. The switch does not send router advertisements (RA). I’m using IPv6 in my lab (Stateless DHCPv6 + SLAAC), so the missing RAs were a problem for me, or at least, annoying. Fortunately you can change the default behaviour. read more

I’m routing on the edge…

In my last post (Routed Port vs. Switch Virtual Interface (SVI)), I have mentioned a consequence of using routed ports to interconnect access and core switches:

You have to route the traffic on the access switches.

Routing on the network access, the edge of the network, is not a question of performance. It is more of a management issue. Depending on the size of your network, and the number of subnets, you have to deal with lots of routes. And think about the effort, if you add, change or remove subnets from your network. This is not what you want to do with static routes. You need a routing protocol. read more

Routed Port vs. Switch Virtual Interface (SVI)

Many years ago, networks consisted of repeaters, bridges and router. Switches are the successors of the bridges. A switch is nothing else than a multiport bridge, and a traditional switch doesn’t know how to pass traffic to a different broadcast domains (VLANs). Passing traffic between different broadcast domains, is a job for a router. A router has an IP interface in each broadcast domain, and the IP interface is used by the clients in the broadcast domain as a gateway.

Switch Virtual Interface read more

Redundancy on the first hop – VRRP

The Virtual Router Redundancy Protocol (VRRP) was developed in 1998 as an open standard protocol. VRRP is the result of an Internet Engineering Task Force (IETF), and it’s described in RFC 5798 (VRRPv3). VRRP was designed as an open standard protocol, but it uses some patents from Cisco. Its function is comparable to Cisco Hot Standby Router Protocol (HSRP), or to the Common Address Redundancy Protocol (CARP). VRRP solves a very specific problem at the network edge: It offers highly available virtual router interfaces, or in simple words: A highly available default gateway. Its home is the network edge, and because of this, VRRP is a so called first hop redundancy protocol. When moving towards network core, VRRP loses importance. If you move from the network edge to the core, redundancy is primarily offered by dynamic routing protocols and redundant links. read more