How to monitor secondary 4G LTE connections in routers
We have a Cisco 4321 router with an LTE card inside. It's been setup that when the primary internet goes down, it will auto failover to the 4G card.
Currently we use snmp to monitor the router based on it's internal IP, but SolarWinds picked up it's external IP on g0/0/0. Because the 4G card is not always active, we cannot monitor that directly. So initially we monitored the routers external IP via a separate ICMP only node. The thought was if the routers external IP was down, but the internal IP was up, then it likely was on 4G.
This worked, but when you do this, then it breaks Netflow as you have two different nodes that are using the same IP. To get around this, instead of monitoring the routers external IP, we monitored the ISP's gateway device (there is no ISP router onsite). Given the gateway could be outside our office, it may not give a good indication when things are down.
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