Hi all,
I’m doing some ECMP test in GNS3 using VSP’s (v8.1.0.0 image).
Setup:
The Cisco is advertising 192.168.1.1/32 via OSPF to VSP1 and VSP2.
VSP1 and VSP2 redistribute OSPF into ISIS using a route-map wich sets the metric to 5000, so I can intercept and deny these redistributed routes on the other VSP using ISIS accept policies. That way, both VSP1 and VSP2 learn 192.168.1.1 via OSPF and both are redistributing it to VSP3.
ECMP is enabled on VSP3, and it correctly learns 192.168.1.1 from VSP1 and VSP2:
VSP3:1(config)#sho ip route
************************************************************************************
Command Execution Time: Fri Mar 27 13:25:19 2020 UTC
************************************************************************************
=====================================================================================================
IP Route - GlobalRouter
=====================================================================================================
NH INTER
DST MASK NEXT VRF/ISID COST FACE PROT AGE TYPE PRF
-----------------------------------------------------------------------------------------------------
...
192.168.1.1 255.255.255.255 VSP1 GlobalRouter 10 4051 ISIS 0 IBSE 7
192.168.1.1 255.255.255.255 VSP2 GlobalRouter 10 4051 ISIS 0 IBSE 7
192.168.1.1 255.255.255.255 VSP1 GlobalRouter 10 4052 ISIS 0 IBSE 7
192.168.1.1 255.255.255.255 VSP2 GlobalRouter 10 4052 ISIS 0 IBSE 7
13 out of 13 Total Num of Route Entries, 6 Total Num of Dest Networks displayed.
--------------------------------------------------------------------------------------------------
TYPE Legend:
I=Indirect Route, D=Direct Route, A=Alternative Route, B=Best Route, E=Ecmp Route,
U=Unresolved Route, N=Not in HW, F=Replaced by FTN, V=IPVPN Route, S=SPBM Route
PROTOCOL Legend:
v=Inter-VRF route redistributed
VSP3:1(config)#
BUT: once it learns the ECMP routes, the CPU quickly goes to 100% and stays at 100% untill the VSP reboots:
VSP3:1(config)#sho k p c
************************************************************************************
Command Execution Time: Fri Mar 27 13:25:53 2020 UTC
************************************************************************************
Slot:1
Current utilization: 100
5-minute average utilization: 17
5-minute high water mark: 17 (03/27/20 13:25:49)
VSP3:1(config)#
If I disable one of the ISIS links on VSP3 and reboot, there is no issue at all. Note that I have to reboot, because once the CPU is at 100%, it only goes to normal level (2-3%) by rebooting it. Disabling one or both ISIS links while the CPU is at 100% does not help.
I can reproduce this every time. Can someone confirm (and maybe explain why?) this is a “bug” related to the GNS3 VOSS VM image?
Unfortunately I don’t have any HW VSP’s available now since I’m homeworking just like the rest of the world 🙂
Config is quite basic, but I can share the configs if needed.
Thanks!
