Category: SNMP

One of my readers has to deal with a crappy Network Termination Equipment (NTE)¹ that does not drop local link carrier² when the remote link fails. Here’s the original ASCII art describing the topology:

PE---------------NTE--FW---NMS 
  <--------IP-------->

He’d like to use interface SNMP counters on the firewall to detect the PE-NTE link failure. He’s using static default route toward PE on FW, and tried to detect the link failure with ifOutDiscards counter.

During the Campus Evolution with Cat9K presentation (I hope I got it right - the whole event was an absolute overload) the presenter mentioned the benefits of brand-new model-driven telemetry, which immediately caused me to put my academic hat on and state that we had model-driven telemetry for at least 30 years.

Don’t believe me? Have you ever looked at an SNMP MIB description? Did it look like random prose to you or did it seem to have some internal structure?

One of my readers decided to build an extensive DMVPN network with BGP as the WAN routing protocol (good choice!) and configured BGP SNMP traps with snmp-server enable traps bgp command on the hub router to detect spoke router failures. It turns out that’s not exactly a good idea.

Brian Christopher Raaen asked a great question in a comment to my OpenStack/Quantum SDN-Based Virtual Networks post:

Other than some syntax difference what do these new HTTP-based APIs add that SNMP couldn’t already do?

Short answer: In theory nothing, apart from familiarity and convenient programming libraries. In practice, there’s a huge gap between theory and practice. See “Hands-on experience” at the bottom of the article.

The snmp-server host command in Cisco IOS has an interesting option: you can specify an URL as the destination host, for example: snmp-server host http://1.2.3.4/xxx traps snmpv2c public. However, I was not able to make it work; the router would accept the configuration command, but the outbound HTTP session never starts. Has anyone managed to get this to work? Any ideas what else is required?

The engineer who wanted to detect specific DoS attack (WAN link overload) with EEM applet asked for something more in his original question: he wanted to receive a SNMP trap on the NMS when the DoS attack is detected. Implementing this requirement with an EEM applet is simple; you just need to add the trap keyword to the event manager applet configuration command.

EEM-SNMP integration is described in the Embedded Event Manager (EEM) workshop. You can attend an online version of the workshop; we can also organize a dedicated event for your networking team.