Support Support Downloads Knowledge Base Case Manager My Juniper Community

Knowledge Base

Search our Knowledge Base sites to find answers to your questions.

Ask All Knowledge Base Sites All Knowledge Base Sites JunosE Defect (KA)Knowledge BaseSecurity AdvisoriesTechnical BulletinsTechnotes Sign in to display secure content and recently viewed articles

[ScreenOS] Packet drop on VSYS due to CPU limit

0

0

Article ID: KB21569 KB Last Updated: 09 Aug 2011Version: 1.0
Summary:
This article describes the issue of packet drop on VSYS due to CPU limit.
Symptoms:
A VSYS (vtest) is facing packet loss due to the CPU limit, but the system CPU utilization is very low. All other VSYS are working fine.

Debug has the following output:
**st: <Trust-vtest|ethernet2/1.x|vtest|7de> 3f9c11c: ff9:x.x.x.x/472d->x.x.x.x/0,1,84
****** 33847572.0: <Trust-vtest/ethernet2/1.x> packet received [84]******
ipid = 4089(0ff9), @03f9c11c
packet dropped, CPU Limit: fast path v4
time billed to vsys vtest
System CPU is as follows:
ScreenOS(M)-> get perf cpu all detail
Average System Utilization: 1% (flow 1 task 1)
Last 60 seconds:
59: 2( 1 1) 58: 2( 1 1) 57: 2( 1 1) 56: 2( 1 1)
55: 2( 1 1) 54: 2( 1 1) 53: 2( 1 1) 52: 2( 1 1)
51: 2( 1 1) 50: 2( 1 1) 49: 2( 1 1) 48: 2( 1 1)
47: 2( 1 1) 46: 2( 1 1) 45: 2( 1 1) 44: 2( 1 1)

Solution:
CPU sharing information between the VSYS's shows that the VSYS vtest is consuming all its allocated CPU cycles.
ScreenOS(M)-> get perf cpu-limit
 CPU Quota %
Vsys Name       Wgt        Cfg %       1 min        5 min       15 min
Root            50         20.0         62           63         59
vaaaa           50         20.0         42           42         39
vcccc           50         20.0         1            2          3
vtest           50         20.0         98           96         97
vdddd           50         20.0         1            2           2

In the output below, it is noticed that a high number of packets are hitting the VSYS vtest and a lot of packets are being dropped.
ScreenOS(M)-> get perf cpu-limit detail vsys vtest
vsys vtest:
Last 60 seconds (paks passed,paks dropped by cpu limit/cpu quota %):
59: 121, 5161/86     58: 135, 6875/99     57: 185, 6200/99
56: 158, 7050/99     55: 764, 4838/99     54: 54, 2567/46
53: 121, 6991/99     52: 163, 6650/99     51: 199, 5892/99
50: 123, 6687/99     49: 114, 6876/99     48: 111, 6995/99
47: 127, 6913/99     46: 238, 5562/99     45: 182, 6324/99
44: 116, 7027/99     43: 70, 7310/99       42: 111, 7279/99
It is apparent that the amount of traffic hitting the VSYS is very high, in comparison to the amount of CPU allocated to that VSYS. Based on the amount of traffic flow, it is advisable to increase the CPU weight for the VSYS vtest, so that it gets the bigger share of the CPU cycles per second.

If you want to increase the time slot for a singe vsys, override it's CPU settings:
ScreenOS(M)-> enter vsys vtest
ScreenOS(vtest)(M)-> set override cpu-weight <value>
ScreenOS(vtest)(M)-> save

Note: The weight allocated to a VSYS should be set after careful consideration. A higher weight on one VSYS will mean lesser CPU cycles are left for sharing between other VSYS's.
Comment on this article > Affected Products Browse the Knowledge Base for more articles related to these product categories. Select a category to begin.

Getting Up and Running with Junos

Getting Up and Running with Junos Security Alerts and Vulnerabilities Product Alerts and Software Release Notices Problem Report (PR) Search Tool EOL Notices and Bulletins JTAC User Guide Customer Care User Guide Pathfinder SRX High Availability Configurator SRX VPN Configurator Training Courses and Videos End User Licence Agreement Global Search