[rancid] Gathering switch information via SNMP or web interfaces

Howard Jones howie at thingy.com
Mon Feb 15 21:34:43 UTC 2016

On 15/02/2016 19:30, Lars Kruse wrote:
> Hello,
> currently I am involved with the maintenance of a dozen switches (Netgear
> GS724T, Netgear GS728TP and Netgear GS748T).
> I would like to distribute notifications to our small group of administrators
> after a switch configuration change was made by one of us.
> As far as I understand RANCID, I assume that it could be used for this purpose.
> Sadly our switches do not allow commandline access (ssh or telnet). They offer
> only a web interface and SNMP.
> I took a quick look at the rancid code and came to the conclusion that it uses
> expect for all its operations. Thus I could imagine that it only works with
> switches with commandline interfaces.
> Please correct my assumptions above, if necessary.
> I am prepared to write some code (extending RANCID or writing single-purpose
> scripts for our environment).
> But I cannot judge if it is possible (and desirable) to extend RANCID in a way
> to would allow the gathering of information via SNMP or web interfaces (with all
> the related complications of sessions and/or cookies).
> Would someone please share some thoughts regarding this approach?
> Thank you for your time!
I used to have some old Nortel/Bay switches that had no CLI. I used 
wraprancid, which allows you to use the output of a script as input to 
RANCID, and then wrote a small perl program that polled the switches 
with SNMP and output a 'cisco-like' config for them, just covering port 
descriptions, speeds and VLAN membership (they were just 24-port 10/100 
access switches). That allowed me to use them with RANCID, and also 
meant that I could drop in 2950s as replacements when they went pop :-)

Interface info comes from the standard IF-MIB and IP-MIB. VLAN 
membership is either a vendor-specific thing or via Q-BRIDGE-MIB. 
Someone on StackExchange is using Q-BRIDGE-MIB with Netgear, so that 
should do it for you. The very basic script could literally be a few 
snmpwalk commands, and leave RANCID to spot the diffs.



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