Why Migrating to IKEv2 Isn’t Optional Anymore
One of the strongest reasons to move from IKEv1 to IKEv2 is the protocol’s security, efficiency, and flexibility — but there's a small detail that often catches engineers off guard:
IKEv2 tunnels reset every 24 hours by design — due to the Security Association (SA) lifetime.
You can confirm this behavior using:
show crypto session detail
You’ll notice the tunnel resets, but traffic isn’t dropped. That’s normal — it's just a renegotiation, not a flap.
But here's the tip:
How do you know if the tunnel actually flapped or simply renegotiated?
Because after 24 hours, the show crypto session uptime gets reset, even though nothing went wrong.
The trick? Use the CEF and RIB tables — they don’t lie.
Run:
show ip rib <route>
If the RIB route uptime stayed stable, you're good — it was just a timer refresh.
If the uptime reset, that's a real VPN flap.
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Pro Tip: Use this method for NOC monitoring or long-term tunnel stability checks. It’s quick, clear, and avoids false positives.
#Cisco #IKEv2 #VPN #Security #RIB #CEF #NetworkEngineering #MigrationTips #Tunnels #ShowCommands #Routing #NetworkOps #NoFluff #RealWorldCisco
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