Tag Archives: networking

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

Stunnel and Squid on FreeBSD 11

I don’t like to use untrusted networks. When I have to use such a network, e.g. an open WiFi network, I use a TLS encrypted tunnel connection to encrypt all web traffic that travels through the untrusted network. I’m using a simple stunnel/ Squid setup for this. My setup consists of three components:

  • Stunnel (server mode)
  • Squid proxy
  • Stunnel (client mode)

What is stunnel?

Stunnel is an OSS project that uses OpenSSL to encrypt traffic. The website describes Stunnel as follows:

Stunnel is a proxy designed to add TLS encryption functionality to existing clients and servers without any changes in the programs’ code. Its architecture is optimized for security, portability, and scalability (including load-balancing), making it suitable for large deployments. read more

How to set a WiFi connection as metered on Windows 10

I switched my mobile carrier and my new carrier doesn’t offer multi SIM (but hey, it’s cheap and sufficient for my needs). Now I have to use my iPhone as WiFi hotspot. No big deal, works perfect. Except one thing: When I was using the built-in 4G modem in my laptop, Windows 10 knew that it was using a mobile (metered) connection, and suspended some services like OneDrive sync, download of Windows Updates etc. That is pretty handy in times of “flatrates” with single digit GB highspeed data volume. read more

Secure your Azure deployment with Palo Alto VM-Series for Azure

When I talk to customers and colleagues about cloud offerings, most of them are still concerned about the cloud, and especially about the security of public cloud offerings. One of the most mentioned concerns is based on the belief, that each and every cloud-based VM is publicly reachable over the internet. This can be so, but it does not have to. It relies on your design. Maybe that is only a problem in germany. German privacy policies are the reason for the two german Azure datacenters. They are run by Deutsche Telekom, not by Microsoft. 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

Setting up split DNS using Windows DNS server

Sometimes it’s necessary to have two DNS servers that are authoritative for the same DNS namespace. This is the case if you use the same namespace for your web site and your internal Active Directory domain, e.g. terlisten-consulting.de. Or that you have created the zone terlisten-consulting.de in your Windows DNS to point specific hosts to internal IP addresses. The DNS servers at your ISP would be authoritative, and the domain controllers of your Active Directory would also be authoritative for the same domain. The response to a query depends on which DNS server you ask. So what would happen if you try to resolve www.terlisten-consulting.de, and the internal DNS has no record for it? read more