Posts

BCMSN Notes -- STP States

2009-05-22 ·3 min read

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 …

bcmsn blocking ccnp cisco forwarding learning listening spanning-tree state stp switch

How Do You Know?

2009-05-04 ·3 min read

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 …

authority engineering social trust

Using SSH to Run Commands on a Router or Switch

2009-04-30 ·3 min read

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 …

cisco cli csm grep privilege router ssh switch

The Most Random Things Can Hurt The Network

2009-04-16 ·3 min read

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 …

bandwidth camera network paper utilization

Server NIC Aggregation to a Cisco Switch

2009-04-14 ·3 min read

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 …

bonding cisco etherchannel ethernet switch teaming

An Interesting Problem with Multiple DCs on a Stick

2009-03-24 ·3 min read

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 …

client csm datacenter linux rip route server vip vlan vserver

RSPANs on Cisco Switches

2009-03-18 ·3 min read

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 …

cisco remote rspan span switch vlan

SPANs on Cisco Switches

2009-03-13 ·3 min read

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 …

cisco monitor span switch tcpdump

CSM Probe Status of ???

2009-02-20 ·1 min read

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 …

cisco csm probe

Fail Actions on CSM Serverfarms

2009-02-20 ·3 min read

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 …

cisco csm failaction serverfarm