If Index used by SNMP (linkDown Trap)

Question: I receive this trap in my trap receiver:

Tue Feb 03 13:49:14 2009 SWITCHNAME- Cisco Agent Interface Down (linkDown Trap) on interface id;nr .1.3.6.1.6.3.1.1.5.3.1.3.6.1.4.1.9.1.283 0

How can I figure out which interface sends this trap?

Answer: In your switch you can use the following command to find out which interface has which index:

sh snmp mib ifmib ifindex

LACP interface in SUSPENDED status

Question: I have a Cisco 3020-HP switch connected to a C6509 by two times 2Gbit trunk links. I configures LACP to bundle two 1Gbit links to form a 2Gbit trunk. One of the trunks works fine but in the other one, one of the links is in "suspended" status. I checked all the settings but could not find any problem; What does susspended status mean?

Answer: When you configure link aggregation, you have to make sure that all physical interfaces and the logical interface (port channel) have the same settings. For instance if you configure a 1Gbps port channel and put one 100Mbps physical interface in that, this interface will be suspended.
In your case these settings match BUT you forgot one thing!!
In your logical interface (Po15) you have 'storm-control broadcast level 30.00' but in one of your physical links (Gi0/20) storm control is set to level 3.00 for broadcast traffic! Maybe a typo mistake. Adjust this setting in your physical link and you will have your interface in the bundle again.

Clear configuration of a removed linecard

Question: I removed a 48 port 10/100/1000BASETX module (WS-X6748-GE-TX ) from my 6509-E switch but the configuration of that module still remains in the running-configuration. How can I clear the configuration of a removed line card?

Answer: Well, this feature has been added to Cisco IOS recently, you need to issue the following global configuration command so when you remove a module, configuration of that module will be cleared,
module clear-config

If you want to negate this feature use:
no module clear-config

HSRP and preempt command

Question: What does "preempt" command do in HSRP configuration. I thought also without this command the router with highest priority will become active.

Answer: To get the role of this command suppose that the active HSRP router fails, in this case the standby router will become active. If no preempt command is used in HSRP setting after the previously active router, the one with the highest priority, comes up again the status of HSRP will not change. This means that the previous standby router, current active one, will stay active even though it's priority is lower.
When preempt is used, whenever a router with higher priority comes up it will become active.

Checking the integrity of a copied file.

Question: I have to upload IOS images to tens of Cisco routers and switches for my company these days; sometimes after I upgrade an IOS and reboot the router (switch) the router (switch) boots in ROMMON. I think images are not copied to flash properly in these cases. Is there a way to see if the image is copied correctly to the flash?

Answer: To check the integrity of the file you copied use the MD5 signature.
Issue the following command to get the MD5 key of the copied file and compare it with the MD5 key provided by Cisco.

verify /md5 flash:filename

After you get the MD5 key go to Cisco.com and try to download the same image in Software Downloads part, just before you download the software you will be provided with a table containing some details about the image and in that table you will find the MD5 key of the file.
Compare it with the one you get as a result of verify command, if they are the same your file is copied properly.

tftp file size limit

Question: I tried to upgrade the IOS on a Catalyst 6509-Sup720 with tftp but I get this error in my tftp server log: "File is too large for tftp protocol". Is this a bug in my tftp server software? If not, how can I upgrade the IOS? Oh I forgot to say that the file size is almost 80MB.

Answer:
Originally tftp protocol supports maximum file size of 32MB, however some changes have been made so tftp can support up to 4GB. But to be practical you need to upgrade your IOS using FTP or RCopy.
To do this with FTP all you need is replacing "tftp" with "ftp" in the commands you used before:

enable
copy ftp: sup-bootdisk:

Of course you need an FTP server instead of a tftp server as well.

If your ftp server requires username and password you have too define them in your switch:

conf t
ip ftp username xxxx
ip ftp password yyyy

Ping all subnets

Question: When I telnet to a switch I can only ping within the subnet of the management VLAN of my switch, how can I ping the other subnets IP addresses?

Answer:

There is an easy way, connect to the switch via it’s console port (con 0) then you can ping every subnet!