Aaron's Worthless Words

Tag: moral

  • BCMSN Notes — STP States

    I’ve decided to take on the CCNP certification, so I’m going to wind up with a few posts will be more my own notes than anything.  🙂 A switch port on a 2960 comes up with a default configuration on VLAN 1.  What happens from the perspective of spanning-tree? First, the port comes up on

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  • How Do You Know?

    I’ve got a non-technical one for you today.  If you’re paying attention to stuff around you, you’ll probably end up with a little paranoia after reading this. We’re having another circuit installed, and the LEC came out to do their end-to-end testing.  The tech, Dan, calls me up on the phone and tells me who

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  • Using SSH to Run Commands on a Router or Switch

    SSH is more than just a shell.  You can copy files from and to a server or piece of network gear with it.  You can use it to tunnel traffic.  Possibly my favorite, though, is to use SSH to run a command on a remote box without interacting with a shell. One of my biggest

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  • The Most Random Things Can Hurt The Network

    This is a great one that I have to share. A couple of coworkers walk in today and ask for some help on an issue.  It seems that a business unit was having latency problems with a web app, and, after research by the product team and sysadmins, nothing wrong could be found.  Lots of

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  • Server NIC Aggregation to a Cisco Switch

    Have you even noticed that your new servers all have 2 NICs on the board?  At least all of them that I’ve seen in the last 3 years have.  A lot of server admin actually use them in a NIC teaming scenario where both NICs are used as one logical device — much the same

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  • An Interesting Problem with Multiple DCs on a Stick

    We talked about running multiple data centers on a stick back in August, which is where you have multiple logical pairs of client and server VLANs on a single CSM for different tiers or functions.  The big point of the article was that you had to do some fancy forwarding to get a server-initiated connection

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  • RSPANs on Cisco Switches

    We discussed SPANs earlier, but let’s talk about RSPANs for a bit. Can anyone guess what the “R” means?  You guessed it — “Remote”.  An RSPAN is a way to get traffic from a SPAN source on one switch to a SPAN destination on another switch that’s connected via a trunk. The basic premise is

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  • SPANs on Cisco Switches

    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

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  • CSM Probe Status of ???

    I must be bored since I’m posting again. A colleague asked me to change the failed value of a TCP probe today.  It was no big deal, but, when I looked to see the status of the change, I noticed interesting stati of the RIPs. switch#sh mod csm 7 probe name TCP80-PROBE detail probe           type   

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  • Fail Actions on CSM Serverfarms

    I’ve talked about probes and stuff on the CSM, but I never mentioned what happens to the connections to a server that fails.  That is, if I’m connected to server A in a cluster and that server suddenly commits ritual seppuku, what happens to my connection through the CSM? Remember how the CSM works?  You

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