Cisco Networking Answers » cisco switch

Cisco Auto MDI/MDIX Switch Support Matrix

MustafaAksu — Tue, 21 Sep 2010 12:58:42 +0000

You don’t need to use crossover cable anymore to connect a switch to another one. Actually, the correct name of this switch feature is Auto MDIX (Medium dependent interface crossover). Let’s make a long story short. You just need a straight-through cable in between PC (MDI type) and switch(MDIX type). Crossover cable is necessary when you have same type in both ends like PC-to-PC or switch-to-switch connection. If device supports Auto MDIX, it changes its port type itself according to other side.

You MUST enable speed and duplex auto negotiation as prerequisite. You have to write down below commands on a Cisco switch to enable it.

speed auto
duplex auto
mdix auto

However Auto MDIX does not supported by all Cisco Catalyst switches.

Cisco Switches without Auto MDIX support
Catalyst 2950
Catalyst 3550
Catalyst 4948

Cisco Switches with Auto MDIX support
Catalyst 2940
Catalyst 2960
Catalyst 2970
Catalyst 3560
Catalyst 3750
Cisco IE 3000

FAQ Section:
Q1) Which pins are in use in MDI &MDIX type ports?
MDI : Pins:1 , 2 transmit 3 , 6 receive
MDIX : Pins:1 , 2 receive 3 , 6 transmit

Q2) Does it work if I use a crossover cable with an Auto MDIX port?
Yes, it does. Both straight-through and crossover cables work fine.

Q3) Can I fix speed & duplex and use Auto MDIX?
No. Auto MDIX use speed negotiation process to recognize other side’s port type. You have to use crossover cable if you want to fix speed and duplex.

Q4) Do I need Auto MDIX on both interface to let it works?
No. It is enough if just one interface supports Auto MDIX but speed and duplex should be auto on both interfaces.

WS-X6516-GBIC is PwrDown after supervisor module upgrade

MustafaAksu — Wed, 05 Aug 2009 18:46:35 +0000

Maybe I am the worst network engineer in the world or maybe I am unlucky.

Recently, I made an upgrade on some of 6509 switches. I bought totally new 6509-E system including chassis, fan, power, and some new line cards. I also insert my fiber line cards that I used in old 6509 with supervisor 2.
Everything was fine until I checked modules status with “show module” command. Switch was up, new line cards were functioning, but my old WS-X6516-GBIC’s were in PwrDown state. When I checked the switch logs I found

00:02:31: %C6KPWR-SP-4-UNSUPPORTED: unsupported module in slot 2, power not allowed: The image for the card is not bundled in image.

What does it mean? I had a recent IOS and it does not support this card. I was not surprised because it happened to me before. I just checked the software advisor tool from Cisco and found another version.I tried it, but it did not work out.

A wise friend of mine told me that I should give a try to a safe harbor image. I was not aware of safe harbor program until that time. Safe harbor images are tested images. They are stable, interoperable and solid. It was my last chance before I should have to escalate this problem.

I found out that there are some problems between Supervisor Engine 720 and WS-X6516-GBIC, but the problem were only valid for 5.0 to 5.3 Hw versions and I had 5.7. It should not be my problem but text mentioned about DFC Sub-modules. I focused on DFC daughter card then. Everything become clear when I found “Catalyst 6500 Series DFC, DFC3A, DFC3B, and DFC3BXL Installation Note” document. I saw a note mentioned below

Note You cannot have a DFC in a system with a Supervisor Engine 720

I removed one DFC (WS-F6K-DFC) from one of the WS-X6516-GBIC and finally it started to work. I also changed the IOS images to safe harbor ones. I spent days to solve this problem and this turned out to be a simple issue for which I got the answer instantaneously from the web!

Before buying an RPS for Cisco Catalyst Switches

MustafaAksu — Wed, 07 Jan 2009 12:18:22 +0000

There are two issues that you have to be aware of when you are evaluating RPS solutions for fixed Cisco catalyst switches. Cisco has a product named Cisco Redundant Power System 2300 (RPS 2300) for the non-modular switch series like Catalyst 3560, Catalyst 3750. This is the successor of old Cisco Redundant Power System 675 (RPS 675).

You have only one bullet in your gun when you have an RPS

Switch draw power from RPS after power fail

You can provide a limited redundancy to your network by installing an RPS for your Catalyst Switches. Switch survives without rebooting when main power goes off. It draws power from RPS, but it never return back to main power. An orange LED shows the switch powered by RPS. If you press the standby/active button on the RPS, your switch will reboot and become a normal operation. The only exception is E series switches + RPS 2300 combination. This combination could restore power state without rebooting.

RPS supports only one switch(in some cases two) at one time

Some of the switches will fail with a power circuit fail

You can attach up to 6 switches to an RPS, but if power Circuit 1 fails as shown in the above scenario then RPS only can support one switch and the rest will fail. RPS 2300 can support 2 switches if power requirements are moderate, but no more.

Standalone or stackable Cisco switches do not support NetFlow

MustafaAksu — Sat, 11 Aug 2007 09:00:19 +0000

NetFlow is a must have technology suitable for mid size to enterprise companies. Nowadays, it has become an IEEE standard as IPFIX (Internet Protocol Flow Information eXport). We will be able to find NetFlow technology support on any brand in the market soon. However, which devices of Cisco itself supports NetFlow technology?

All routers including the oldest (e.g. Cisco 2500 series) and smallest (e.g. Cisco 800 series) support NetFlow. Some functions does not exist in older IOS versions.
Catalyst 6500 series switches support NetFlow. Catalyst 4500 series switches support NetFlow with Supervisor IV/V + WS-F4531 Catalyst 4500 NetFlow Services Card.

Standalone or stackable switches do not support NetFlow. This means Catalyst 4948, Catalyst 3750 or Catalyst 3560 series switches do not support NetFlow. You can see the necessary commands on config mode, but they are not effective. It is not about IOS version or feature set. You need a modular switch for NetFlow.

Unfortunately, the answer of “What Cisco switches support netflow?” is only the modular switches.

HSRP Group IDs are limited to 16 on PFC2

MustafaAksu — Sun, 29 Jul 2007 15:17:40 +0000

On the catalyst 6500 switches, the maximum number of HSRP group IDs are limited to 16 in the Supervisor Engine 2-based systems. This limit is 256 in all other older and newer systems.If you try to create a new standby group after this limit you recieve

More than 16 standby groups not supported in this platform.

message.Cisco says that this is a per interface limit. So, you can use same ID in several interfaces.

You can find the details on “HSRP Group Limitation on Catalyst 6500/6000 Series Switches Frequently Asked Questions”