CCNP Route - debug?

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In a couple episodes, one being Policy-Based Routing it stated that the amount of data being outputted from debug ip policy is so great that you would want to run it from the console and not from telnet or VTY, is there a reason for that?

I thought that when output was great, the VTY is where you would want ot run such commands.

From Ciscos site: Warning: Excessive debugs to the console port of a router can cause it to hang. This is because the router automatically prioritizes console output ahead of other router functions. Hence if the router is processing a large debug output to the console port, it may hang. Hence, if the debug output is excessive use the vty (telnet) ports or the log buffers to obtain your debugs. More information is provided below.

@kevin-platkowski,

I'll try to reach out to Don today. I'm not sure if this just a simple word jumbling or if had a reason.

@kevin-platkowski ,

From Don:
"Using the VTY will drop packets if it is excessive data resulting in better performance, but incomplete data. Using the buffer ensures good performance as well, but has a limited size which can result in overwritten log entries. The console has limited bandwidth (only 9600bps by default) but you can always issue an 'undebug all' regardless of status. All three methods have their pros and cons. The true best solution is to not excessively log in the first place as it is rarely necessary."

I'll only add that Don's answer does agree with the cisco article you found: It's not that you can't issue debugs but should be aware too much output is something that you must consider when using debugs. If you don't you can over the routers available resources depending on the router.

So Don's explaination is that it's not a mis-statement it is in his experience that if you need "undropped" logging information then it may hang through the console but vty may perform better but you'll get packets but possibly not all of them since vty will automatically drop packets to keep the logging going.

@ronnie-wong Thank you!

@kevin-platkowski ,

glad to help and glad you're a member!