Common operational misconceptions

Jack Bates jbates at
Thu Feb 16 01:20:38 UTC 2012

A few for me that come to mind which haven't been covered yet.

*) Latency, jitter, etc when pinging a router means  packets going 
through the router suffer the same fate.

Never fails that I get a call about the latency changes that occur every 
60 seconds, especially on software based routers. uh, huh.

*) admin/admin is okay in a private network behind a firewall

Oh, look, a console port!

*) Assign arbitrary MTUs in a layer 2 transport network based on exactly 
what customers order.

*) MTU/packet/frame/ping size means the same thing on all vendors.

*) If Wireshark looks right, it must be right (unless Windows discarded 
1 (and only 1) layer of 802.1q tags)

*) Upgrades should always be done, even when there's no relevant 
security or functionality that is needed in newer code.

Amazing how many code changes break things which don't necessarily show 
up in test environments but will show in production networks (Your mpls 
worked for months with an invalid router-id configured, and then broke 
when you change codes? DHCP worked fine, but after upgrade quit 
accepting <300 byte DHCP packets?).


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