Q: How do I stage a new IOS on a 3750 switch stack?

A:

There are some new IOS commands to automate upgrading of a stack, but I use the familiar manual method.

All of your stack members really should be running the same version of IOS (even though there's a chance that if the versions are close enough the stack might still work).

Upgrading a switch is like upgrading a router, really. You put the new IOS on the TFTP server. Make sure there is room for it in the flash of the target device, and tftp it up. When you are ready to start using it, change the boot system command on the device to point to it, and reload.

What makes switch stacks different is that you need to copy the IOS to all of the switches. Here's how.

• Log into your stack. (You'll be logged into the master). Do show stack to find out how many switches are in the stack, and which one is the master. Let's say there are four switches and the master is 4.
• Use copy tftp flash: and answer the prompts to get your IOS up there.
• You can do dir flash: to see that the new IOS is there. When you refer to "flash:", you are always referring to the master. You can also refer to a particular stack member's flash like this: dir flash2:. So on this stack, where 4 is the master, dir flash: and dir flash4: will look the same.
• Now get that IOS image onto the other switches in the stack. You can either tftp it to each in turn with copy tftp flash1: and so on, or use copy flash4: flash1:. The copy method is only a little quicker, but it works.

Q: Do I have to worry about the U.S. DST change on my routers and switches?

A:

No, not likely. Even if your device is an NTP server for the rest of your network, the timezone really does not matter. The device's timezone settings does influence the timestamps on the router logs and the syslog messages it sends. It could also come into play if you are using time-based ACLs on your router (does anyone actually do this?). However, if you really want the local time on the router to be correct, you do not have to upgrade the IOS to a version that incorporates the new United States DST start and end dates. Just by adding one line to the config on your router or switch, you can change the DST policy. I'll show both timezone lines for my devices; you will want to change the timezone name in both lines (which is used for display purposes only) as well as the offset from UTC unless, like me, you are in the Eastern time zone.

clock timezone EST -5
clock summer-time EDT recurring 2 sun mar 02:00 1 sun nov 02:00

Q: I found a router that had cef enabled, but "no ip route-cache cef" on each of its interfaces. Is there any reason not to enable cef on the interfaces?

A:

Haven't found any reasons not to enable cef on the 2600XM interfaces. If you know any, please post a comment...

Q: Why isn't my router clock syncing to NTP time?

A:

If the difference between the NTP time received and the local clock time is more than 4000 seconds, the router or switch will not sync to the NTP time except:

• on reload
• when the NTP peer is first added to the config