Switching

HP SAN P4300 Performance

Posted by robd on April 04, 2014
Networking, SAN, Server / No Comments

We had some issues a while back where there was latency between a PC and SAN so I started to look at all the layers to try and find a problem, here’s my findings in case anyone finds it a interesting read.

To rule out the PC, I’ve tested the performance of the SAN and network throughput.

The performance of the SAN which is based in IOP’S (Input/Output Operations Per Second) and the current average total is 800 (found on the SAN info page).  To put this prospectus, a poor performance would be in the 2000’s.

The below graph only shows output from 17:28 but has been running all day meaning the average should be accurate:

SAN1

Looking at the performance of switches can be difficult, but we’ve started using HP Intelligent Management Centre which is great at collating stats. The switches reported low bandwidth, CPU, memory and I/O seemed normal:

Switch1

We know from experience the throughput on these switches is limited by infrastructure in our case 1GB fibre.

These are the theoretical Max Sequential (SEQ) write limits we could obtain from our connection to the SAN (in practice there is a  5%-20% overhead involved):

SAN2

I’ve managed to very roughly test this write limit from a client to the SAN SAS disks:

SAN3

A result of 81.12MB/s is very positive, considering we can realistically over ever achieve 125MB on our current setup.

What this meant in my opinion was the SAN and network were not to blame meaning it was either client or server….Long story short the AV on the server was causing our latency not the “network”.

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HP Switch – Access control Lists

Posted by robd on April 04, 2014
Networking / No Comments

Hi All,

We’ve recently implemented a BYOD wireless SSID for end users to check facebook or what ever it is they do.  As we’re short on resources we had to use existing DC’s to doll out IP’s but we were obviously worried around users “hacking” into the system.  So first thing we did was create a VLAN and assigned it to the wireless then applied several access control lists (ACL’s) to the core switch limiting the access to only the DC’s, proxy, core switch, each other and firewall then blocked the rest:

Firstly check the subnet mask of the VLAN you want to apply the ACL too as the wildcard/subnet address in the ACL will change dependant of the subnet.

The below example will use a subnet mask of 255.255.255.0 (the bits in red are notes only – do not try and apply them)

Logon to a switch and go into config mode:

 

Finally test!

Ok so what if you have a network that has a subnet of 255.255.252.0, well the wildcard changes in the ACL or above we had 0.0.0.255 where as in a 255.255.252.0 subnet we’d need 0.0.3.255.

Example:

 

So what happens if you want to delete a ACL from a VLAN:

 

 

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IP Routes

Posted by robd on March 29, 2014
Networking / No Comments

Hi All,

Started at a new company recently and they’ve had a ongoing issues for ages where they could only access one of two switches in their server room if they were on the same subnet.

So Switch A was the problem switch and had a IP of 10.0.0.123,

Switch B they could access from anywhere and had a IP of 10.0.0.124.

My Computer had a IP of 192.168.111.1.

So initially I started thinking the issue was down to vlans as we have around 50 vlans and I kind of just presumed it would be a issue with cross vlan routing.  Well actually I was wrong.

Firstly I pinged both switches:

SwicthA – Can not ping.

SwitchB – Can ping.

Next Trace route (TraceRT from a win 7 PC)

SwitchA – Could not trace

SwitchB – two hop trace, Core switch then the switch.

Ok so what next…..Lets try the above from the switches (so after connecting to server on the same subnet I ran the tests):

Ping my PC:

SwicthA – could not ping,

SwitchB – could ping.

Trace route:

SwitchA – No route,

SwitchB – two hop route.

So after this I decided it must be a routing issue, as both switches could ping the core switch and both switches could trace route the core switch.  So lets have a butchers at the routing.

 

Hold the phone, there’s no sodding return route to the core switch (10.0.0.2)

So I added the route like so:

And bobs your uncle it worked!!

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HP Swicth – Show everything to a TFTP Server

Posted by robd on March 27, 2014
Networking / No Comments

So How do I send the output of the “show tech all ” command to a TFTP server?

Easy.

Launch the TFTP server (i.e. TGTPD64 from HERE), and issue this command at the CLI of the switch:

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