Layer 2 looping in network

[prince.p]

Hi friends 

we are using  sonicwall NSA 2400 series firewall with 46 mbps leased line connection. most of the time my firewall cpu utlization gets nearly 98 percent . due to this my network is getting struck. we are using 2 cisco 2960 series switch. in this one of the switch we connected with vlan1 interface in gi0/2 and vlan2 in gi0/4 and dmz in gi0/29. when we contact firewall support,they informing that there is an looping in the network and they are suggesting us to use layer 3 switch for dmz zone or they want to connect dmz in seperate switch layer 2 switch.i need your support that will layer2 loop will occur due to DMZ interface connected in the switch  or anything else below i attached our network diagram

[Reza Sharifi]

Hi,

Is the Firewall the gateway for all 3 vlans? If you to test this, you can use only one of the 3 links from the switch to the firewall and trunk the interface on the switch with all vlans (1, 2 and 5) and create sub-interfaces on the firewall (if possible) and put each vlan IP on a Sub-interface.  This way you don't have multiple links from the switch to the firewall (you only have 1) and this eliminate the possibility of any loop.

HTH