ERSPAN on Nexus

Today, while troubleshooting a reported SIP trunking issue, I was seeing a firewall claiming it was transmitting packets, but they were not seen by the downstream endpoint. I didn’t trust the ASA packet capture in this case, so I decided to collect traffic from its immediately-connected device, a Nexus 7009, to verify. Cisco has a technote for a configuration example on this platform. ERSPAN is handy to be able to do ad-hoc troubleshooting when you need to a packet capture from a remote device, so I configured an erspan-source session to capture traffic on that particular interface and sent it to a remote Linux machine....

March 1, 2022 · 2 min · Jason Lavoie
[Mixed]( by [RyanMcGuire]( licensed under [CC0](

Network in OSPF database but not in routing table

I needed to troubleshoot a pesky OSPF issue on a new network. It turned out it was a simple fix, but had tripped up a couple other network engineers so I thought I’d lab it up and document the scenario. The problem The reported issue was that a network that was part of the OSPF process was not showing up in the routing table. Adjacencies between all routers were up and the network in question was shown in the OSPF database....

November 16, 2021 · 5 min · Jason Lavoie