FATMIN

TCPDUMP Tricks -- Find a Port's Configured Vlan and Port Number

So this was a new one to me. I never knew that you could get a network ports vlan configuration using Tcpdump.  In the past I've used cdpr to determine an interface's uplink port, but I never knew that you could use tcpdump to get the same information and also determine the VLAN.

Note that I did not discover this one myself. So if you happen to be the person who told me how to do this, thanks and pipe down.

Anyway here is the command, note that my interface is em1, your's will probably be different.

tcpdump -nn -vvv -i em1 -s 1500 -c 1 'ether[20:2] == 0x2000'

From the command above you get a nice little bit of output, which you have to poke through a bit to get the meaty parts out. Hey look its my port, and the name and ip of the switch upstream.

Device-ID (0x01), length: 27 bytes: 'SW2.corp.example.com.'                   
Address (0x02), length: 13 bytes: IPv4 (1) 172.22.10.254                           
Port-ID (0x03), length: 16 bytes: 'FastEthernet3/28'

Now check out this sweet nugget. A VLAN!

Native VLAN ID (0x0a), length: 2 bytes: 246

 

TCPDUMP Tricks -- Find a Port's Configured Vlan and Port Number

So this was a new one to me. I never knew that you could get a network ports vlan configuration using Tcpdump.  In the past I've used cdpr to determine an interface's uplink port, but I never knew that you could use tcpdump to get the same information and also determine the VLAN.

Note that I did not discover this one myself. So if you happen to be the person who told me how to do this, thanks and pipe down.

Anyway here is the command, note that my interface is em1, your's will probably be different.

tcpdump -nn -vvv -i em1 -s 1500 -c 1 'ether[20:2] == 0x2000'

From the command above you get a nice little bit of output, which you have to poke through a bit to get the meaty parts out. Hey look its my port, and the name and ip of the switch upstream.

Device-ID (0x01), length: 27 bytes: 'SW2.corp.example.com.'                   
Address (0x02), length: 13 bytes: IPv4 (1) 172.22.10.254                           
Port-ID (0x03), length: 16 bytes: 'FastEthernet3/28'

Now check out this sweet nugget. A VLAN!

Native VLAN ID (0x0a), length: 2 bytes: 246

 

Basic AIX Performance Troubleshooting Commands

Wow, today I logged into my first AIX Server in about 4.5 years. It was a horrible experience. I've been working with Redhat/CentOS pretty much exculsively for so long, I was mostly helpless to do anything of importance on the CLI other than create a few users and move some files around.  None of the common commands that I am so used to using even exist in AIX.

Figured I would do a bit of homework and figure out how to do some basic troubleshooting before I was in a server down situation with no idea how to troubleshoot.

Checking Free Memory

To check free memory on a box use the svmon command.

svmon -G

Overall System Status

For this you will probably want to use topas, which is pretty simiar to top. Topas gives you a quick and dirty overview of what is going on on a system. Here you can find CPU usage, top processes, disk utililization. Check out the fancy screen shot below.

List Volume Groups

Wow, Linux has really confused me on this one. Anyway, use lsvg

# lsvg -o
rootvg
crsrdb_bin
crsprdb_data
crsprdb_index
crsprdb_arch
crsprdb_rman

List Info About a Volume Group.

# lsvg rootvg

Display Names of all Logical Volumes in a Volume Group.

# lsvg -l rootvg

Display Physical Memory

# lsattr -El sys0 -a realmem

Finding Disk I/O Issues

Sar appears to be a fine option here. Especially since I am looking for percent busy. Iostat also exists on AIX, btw.

# sar -d 1 2

Show Network Throughput

The more I poke around the internet trying to figure out how to actually use AIX the more I keep running into topas. Anyway this one is a good one

#topas -E

I plan to have more of these one liners documented here in the future, but for now this is going to have to do.

 

Using Yum Update to Apply Security Patches Only

So I recently moved to a new job where we are running full blown enterprise Redhat Linux. RHEL 6 to be exact. Being a big Redhat fan, and Certified Redhat Engineer I was pretty excited to play with the real thing and kick CentOS to the curb for a while. I was not dissapointed as my first couple of weeks on the job turned into a crash course in Satellite Server and the Redhat Linux Life Cycle.

Specifically I needed to figure out how to fix a couple of security vulnerabilites in 6.3 which patches that were only part of 6.4, and could not be found in the official RHEL 6.3 repos. Side note however, I was not allowed to update the server completely to RHEL 6.4.

Thankfully I found a few simple commands that helped me hack together this Frankenstein.

#yum --security check-update

The command above will list any and all security updates that are availbile, then you can run the command below to install them

#yum update --security

Another cool command is shown below.

#yum list-security

This command gives you the CLA code for each fix which you can then use to obtain more information on the fix

#yum info-security CLA-2012:1353

 

 

 

Ubuntu Linux- Locate Failed Dimms without Pain

So I have recently made the switch to Kubuntu 12.10 on my new desktop. Basically I am building a monster workstation and I ran into issue running Fedora 18. Since I wanted Steam support too I decided not to try to move to an earlier Fedora version, but rather, I chose to  give Ubuntu another try (its been years since I have run Ubuntu).

Anyway, I am building this hoss of a work station that has 12 Dimm slots, which I fully populated with 4GB dims. However when I booted my new monster, I found that I was 8GB short in the Memory department.

So, how do I figure out which two dimms are bad? I certainly dont want to have to pull all of them out and boot the machine and test each dimm one by one.

So this is where lshw comes to the rescue. Which I blogged about back in 2010 here.

Anyway. Here is how you find the empty slots.

# lshw -short -C memory

which output what you see below.

0/14                           memory      System Memory
/0/14/0                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/14/1                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/14/2                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/14/3                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/14/4                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/14/5                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/22                           memory      System Memory
/0/22/0                         memory      DIMM DDR3 [empty]
/0/22/1                         memory      DIMM DDR3 [empty]
/0/22/2                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/22/3                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/22/4                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)
/0/22/5                         memory      4GiB DIMM DDR3 1066 MHz (0.9 ns)

Basically this is telling me that my first two dimms on CPU two are dead and are the ones that need to be replaced.

Now all I have to do is powerdown and pull and replace two dimms.. which will save my fingers from much discomfort.

I have no name! - RHEL 6 and SSSD Issue.

This is an interesting one that I ran into today on an RHEL 6.3 VM that is using SSSD for authentication against LDAP.

User contacted me stating that he was unable to su to a particual user.

# su – app

cannot find name for user ID 650

[I have no name!@localhost ~]

So I jumped on the box and attempted to "finger" the user "app". This command retured the expected output, as did the "id" command. Thinking that the issue was a temporary failure for the server to connect to the ldap server, I figured we were probably fine now. But when I attempted to su to the user above, I ran into the same issue that the user ran into. So I restarted sssd and tried again. Same issue. So in order to isolate the issue a bit more I then attempted to su to another user, and was successful.

Huh?

Remebering that I had run into a similar issue before I decided to stop sssd and then delete its cache

service sssd stop ; cd /var/lib/sss/db ;rm cache_default.ldb; service sssd start.

Boom, su now works like a charm.

A bit of research shows that this is a known issue. See bugzilla here.

Also I could have used the ldbsearch command to verify that the particular users database/cache entry was corrupt.

ldbsearch -H /var/lib/sss/db/cache_default.ldb uidNumber=650

 

Vmware VCenter Virtual Appliance - Death to Windows.. I think.

I am, and have always been, a Linux/Unix Administrator, until VMware forced me to learn a bit of Windows.

This, above all, has been the very WORST part about Vmware. Just to run Virtual Center, I had to BUY Windows, I had to Install Windows, and I had to try to learn Windows.  Oh, and then I had to slap some sort of virus protection on it, and figure out how to patch it. And then worst of all try to authenciate to it, as I am not administering Active Directory. No, I use Openldap, as any Linux/Unix admin would.

Then on top of that I needed Windows to even run the VCenter Client and Connect to my VCenter Server.  Well hell, I don't run Windows, not even on my desktop, not even on my laptop... not at home and not in the office. Its been this way for 5 years and VMware, is not going to make me change this.

Now, flash forward to VSphere 5.1, and low and behold, what is this. A real, fully functioning, web client for VCenter. Ok now we are getting somewhere. Now, I have not had a ton of experience with it, but my first impressions are pretty good. Its flashy, its fast, and it appears to be fully functioning.

To further make my day, the Vmware VCenter Appliance is now no longer beta (this is probably old news to most). For those who are not in the know, its Linux (albeit Suse).  So I am downloading it now and am going to give it a spin. How fully functioning is it... I have no idea. Do I need a database somewhere or does it have one built in? I do know it can connect to oracle, which is really neat, but not as neat as postgres or mysql. Also, how awesome would it be if I could configure the thing to use Openldap for auth?

Dunno all the answers yet, but I should have more insight on the topic soon, so stand by.

 

Related articles

vCenter Server 5: Important Tip while Installation

How to Reset Cisco Catalyst 2960 Back to Factory Defaults

This is my first post in what I hope to be a long line of Cisco networking related posts, as I have just gotten my hands on a bit of used Cisco equipment and hope to use it to setup a home lab.

First step of setting up this home lab is to get my two Catalyst 2960s reset to factory defaults. So here is how you do it. Note that I am assuming that you have already established a console connection to the switch.

First boot up the switch while holding down the MODE button untill you see the following appear on the screen

Switch>
Boot Sector Filesystem (bs) installed, fsid: 2
Base ethernet MAC Address: 00:17:0e:17:de:80
Xmodem file system is available.
The password-recovery mechanism is enabled.

The system has been interrupted prior to initializing the
flash filesystem.  The following commands will initialize
the flash filesystem, and finish loading the operating
system software:

    flash_init
    boot

Then type flash_init

switch: flash_init
Initializing Flash...
flashfs[0]: 547 files, 19 directories
flashfs[0]: 0 orphaned files, 0 orphaned directories
flashfs[0]: Total bytes: 32514048
flashfs[0]: Bytes used: 15487488
flashfs[0]: Bytes available: 17026560
flashfs[0]: flashfs fsck took 11 seconds.
...done Initializing Flash.

Check out the contents of flash and delete confit.text and vlan.dat (if it exists).

switch: dir flash:
Directory of flash:/

    2  -rwx  564       <date>               vlan.dat
    3  -rwx  1914      <date>               private-config.text
    5  drwx  192       <date>               c2960-lanbasek9-mz.122-58.SE2
    6  -rwx  3096      <date>               multiple-fs
    7  -rwx  2289      <date>               config.text

Now delete the vlan.dat and config.text

switch: del flash:config.text
Are you sure you want to delete "flash:config.text" (y/n)?y
File "flash:config.text" deleted

switch: del flash:vlan.dat
Are you sure you want to delete "flash:vlan.dat" (y/n)?y
File "flash:vlan.dat" deleted

Now type boot, to reboot the switch. Once the switch is rebooted you will see the System Configuration Dialog, and will have the opportunity "to enter the initial configuration dialog"