If you have ever been blacklisted for sending spam there is a good chance the source of those emails was not your mail server but a compromised computer inside your network. So, how do you combat this? Well, the easiest way is to create access lists on your firewall to only permit your mail server to send out on port 25 (SMTP). For a Cisco ASA, this can be easily accomplished with 4 lines of code.[Read more…] about Block spambots on compromised PCs
While this isn’t exactly ground breaking stuff I thought it might serve as a nice refresher to those that dabble in the Cisco CLI. These are a few commands you can never do without.[Read more…] about Three Cisco IOS commands you can’t do without.
I was recently building a VMware ESXi multi-host environment with a LeftHand Virtual SAN and I needed 6 Port Groups for my design. I already had one pre-existing Port Group that was a 2GB uplink to my Layer 3 switch.
Everything was going great until I tried to create Port Group number 7. This seemed odd to me as I knew my IOS version should at least support 128 Port Channel Groups.
After some digging, I discovered this 2960G only supports 6 Port Channel Groups. This was unfortunate but not a deal-breaker. I knew I would not be using Vmotion very often on this cluster so I let that run on a single Gigabit Ethernet port. This allowed me to re-architect my solution for only 4 Port Channel Groups.
Just thought I’d pass this one along. You don’t often see switches restricted to this few port-groups.