MAC addresses in a VSS cluster

As you might know, creating a VSS on Cisco Catalyst 4500-X switches is pretty easy and there are many many guides with information how to do this. I think THIS guide is one of the best to do this.

However, there is one additional note which is not mentioned on that (and other) blogs if you are planning to use multiple Catalyst 4500-X VSS clusters. This is related to the switch MAC address.

By default, all MAC addresses used by the Catalyst 4500-X VSS cluster is automatically generated and is based on the VSS domain ID. But what does this mean?

If you’re planning to use multiple VSS clusters in the same network and in the same VLAN(s), you’ll end up with duplicate MAC addresses. I’m sure I don’t have to tell you that this is something you don’t want: it brakes a lot of things in your network.

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Cisco WSA Deploying Proxy Services

In this and other posts we’ll discuss the Cisco Web Security Appliance. This is the blog agenda:

Part 1: Introduction
Part 2: Installing
Part 3: Deploying Proxy Services
Part 4: Policies
Part 5: Acceptable use & HTTPS Inspection
Part 6: Authentication
Part 7: Defending malware

This is the 3th blog in the series about the proxy configuration.

There are a two proxy modes:

  • Explicit Forward Mode
  • Transparent Mode

In Explicit Forward Mode the client does have an Proxy configuration. There is no configuration needed on the network infrastructure (routers/switches). Authentication is easy and there are three methods for providing the proxy information:

  • Automatic Proxy script
  • Enter the proxy server IP address
  • Automatic detect settings using WPAD protocol

In transparent mode, there is no configuration needed on the clients. The network infrastructure redirects the traffic (WCCP). Authentication could be an issue.

Redirection options are:

  • Web Cache control protocol (WCCP, used in Cisco ASA, ASR and Catalyst switches)
  • Policy based routing
  • Layer 4 switch
  • Layer 7 switch (like a Citrix Netscaler)

WCCP is the most used redirection option for transparant proxies. For more information about WCCP and the configuration, check this link.

PAC files

PAC files are used in Explicit Forward Mode. The PAC file link is configured on the clients’ proxy settings. If you need help with creating PAC files, check this link.

You can host the PAC file on any webserver, but hosting on the WSA is possible too. Click Security Services > PAC File HostingĀ  and upload your PAC file. It’s recommended to host the PAC file on a seperate web server.

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