On Thu, Nov 5, 2009 at 1:44 PM, Les Mikesell lesmikesell@gmail.com wrote:
Larry Brigman wrote:
You could define a class that runs a script to detect the network settings, if it is forced to full duplex it would return true, which would then trigger another command to run or config files to get copied, if configs are copied after that it could execute another command(perhaps snmpset to change the switch config or something).
It's next to impossible to get or set a duplex setting via snmp. And non-trivial to figure out what switch port is connected to what device - OpenNMS does a reasonable job but if you activate all of its checks it can kill things that have full bgp routes.
Saw something about this at LinuxCon. CME is using Cisco Discover Protocol and LLDP to figure out the info about the connected port, location, vlan and a bunch of other stuff.
That's interesting, thanks! I was surprised to see that cdpr (from epel) would pick up the name/ip/port from a connected Dell PowerConnect switch. But then I repeated it using the -v option and it found the upstream Cisco instead... The production switches are all Cisco though, so this might be a usable hack to permit pre-configuring machines to adjust themselves to whatever order the cables happen to be plugged in. The duplex option just shows a number and doesn't offer to interpret the value, but maybe I can look that up somewhere.
cdpr is multicast udp packet. Other devices not Cisco will pass this on. Other Cisco devices will drop it since it is really only useful between devices. Other switch vendors wanted to be more vendor neutral and came up with the LLDP (Link Layer Discovery Protocol) which I don't think is on cheaper switches. The other think about CDPR is that unless the network admin has explicatlly turned this off, it is "on" by default in all Cisco gear.
CME's basic usage model was to use this to notify the networking group about a mis-configuration by pointing them to the exact switch/port by name and number. They use nothing but Cisco gear.