Question regarding load balancing UDP traffic, one armed mode on CSS

Answered Question
Nov 13th, 2008

Hi, I'm trying to set up a CSS so it will forward SNMP traps (UDP 162) to a back end service. The config for this should be very simple, I shouldn't have any requirement for source groups as there is no return traffic, the only doubt in my head, is whether or not this will work if the traffic comes in on one vlan and goes back out of the same interface on a different vlan.

For my test, the source address is, and the trap destination is (the VIP).

Our HTTP rule works fine, but this SNMP rule doesn't. If I sniff the CSS port, I can see the trap going to the CSS, but if I do sh summary on the CSS, I dont see any hits on the SNMP rule. The service is up.

Can anyone offer any advice on this?

I'll paste the config below.

Many Thanks in advance


CSS11503# sh run

!Generated on 11/13/2008 09:23:00

!Active version: sg0710102


!*************************** GLOBAL ***************************

ip route 1

ip route 1

!************************* INTERFACE *************************

interface 1/1

description "trunk port to EH_4507"


vlan 6

vlan 7

vlan 200

!************************** CIRCUIT **************************

circuit VLAN1

ip address

circuit VLAN6

description "MGT interface"

ip address

circuit VLAN7

ip address

circuit VLAN200

description "VIP VLAN"

ip address

!************************** SERVICE **************************

service CUSA_TRAPS

ip address

protocol udp

port 162

keepalive type none


service WEB

ip address

keepalive type none


!*************************** OWNER ***************************

owner CUSA

content TEST

vip address

add service WEB

protocol tcp

port 80

url "/test/*"


content TRAPS

vip address

protocol udp

port 162

add service CUSA_TRAPS


I have this problem too.
0 votes
Correct Answer by Syed Iftekhar Ahmed about 8 years 2 months ago

By default CSS doesnt setup flows for SNMP traffic.

Please read the following for details

You need to apply the following command

flow-state 162 udp flow-enable

Syed Iftekhar Ahmed

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