Reoptimization timer
Load mpls.te.base.config.with.ospf.cfg
Configure bi-directional TE tunnels between CSR8 and XR11, and between CSR8 and CSR5.
Simply use a dynamic path option.
Configure R8, R5, and XR11 to reoptimize all tunnels every 1 minute, and whenever a linkup event happens.
Configure the R8-XR11 tunnels to never reoptimize.
Answer
Explanation
MPLS traffic-eng tunnels are re-calculated using CSPF at the reoptimization interval, or upon a link-up event (if configured). The default reoptimization interval on IOS-XE and IOS-XR is 60 minutes. To change this interval, we can use the following commands:
We can also simply execute reoptimization from the CLI in exec mode on both platforms:
Finally, we can configure the router to run CSPF upon a linkup event to reoptimize all tunnels immediately:
Verification
On R8, we can verify that the tunnel to XR11 has lockdown enabled on the path-option. This means that the path-option should never be re-optimized. This is a way to completely prevent reoptimization for this particular path-option.
We can see this on XR11 as well:
On R8, we can run debug mpls traffic-eng tunnels reoptimize detail to watch reoptimization events. We’ll see that every one minute, the “should_reopt” value is TRUE for Tun5. Additionally, only tun5’s path-option 1 seems to be activated for reoptimization. We never see Tun11 show “should_reopt: TRUE”. This appears to be due to the lockdown command on the XR11 tunnel path-option.
If we flap a link on R8, this should also cause immediate reoptimization upon the link-up event. We’ll increase the optimization timer to make sure the reoptimization happens due to the event, and not the periodic timer.
Before we make any changes, notice that every 30 seconds the router appears to run a check for whether reoptimization should occur. Every 30 seconds it is always “FALSE” now, because the reoptimization timer is so high.
Next we’ll flap a link on R8. Watch how reoptimization is triggered by the IGP adjacency coming up. Interestingly, the reoptimization process seems triggered at link-down, link-up, and IGP-up. But only IGP-up seems to actually cause reoptimization. Perhaps “link-up” means that link is up from the TED perspective, which only occurs once IGP is up.
We can use the same debug command on IOS-XR: debug mpls traffic-eng tunnel reoptimization. We see that reoptimization is running every 60 seconds.
If we flap a link on XR11, we should see reoptimization kick in due to the link-up event. This gives us much better output than on IOS-XE. We can also clearly see that the tunnel to R8 is not a reopt candidate because the path-option is locked down:
Last updated
