We’re working on an data center design for a customer, and they’ve dropped in two ISP links - each with it’s own managed router and public IP space off one of the Ethernet interfaces.  The idea is that they want to use the Internet links in an active-passive setup without getting their own IP addresses to avoid running BGP with the ISPs.  To top it off, the headend of their control is an ASA cluster, so we wind up with two interface on the Internet to treat with a local security level.  Oh, the joys of doing network design.

I can’t believe I haven’t blogged on this yet.  SPANs are one of my favorite things in the world.

The switched port analyzer (SPAN) is a mechanism on Cisco switches that allows you to take traffic on one port and copy it to another.  It’s generally used to get traffic to a sniffer or IDS for analysis, but it’s a great tool to use to sample traffic from a host for troubleshooting.