Problem with 5500G-EI producing many Gratuitous ARP's

[jerrycb]

Hello,
I'm having problem with my network. On the network i'm seeing lost of broadcasts. With Etheral I found out that most of the broadcasts are beeing produced by the backbone switch. (3Com 5500G-EI)

The layout of the network is as followed: It has a 3Com 5500G-EI as a backbone switch (for Servers) with 4 4400 switched (for clients) connected to it by 1000Base-X Gigabits Ethernet SFP's ports

The 5500G-EI is producing lots of Gratuitous ARP's.

Most of the G-ARP's are beeing send from 192.36.253.11 to 192.36.253.11 (using 2 different MAC adresses)

Is there a possibility to reduce the Gratuitous ARP's from the device to it self?

and second, Can I reduce the rest of the ARP's broadcasts?
I read sommething about larger ARP caching. How can I set that on the 5500 switch.

Can you please help me?
Thanks,

JerryBoz

 

[scottaobe]

Hi Jerry,

I had this same issue when we installed a 3Com 5500G - here is a short excerpt from SuperStack® 4 Switch 5500 Family Configuration Guide (PDF DUA1715-0BAA01.pdf) page 79

http://support.3com.com/infodeli/tools/switches/5500/DUA1715-0BAA01.pdf

You should probably look at the complete documentation and make sure there won't be any unintended consequences depending on the rest of your network and equipment but this should get you pointed in the right direction.

I wound up disabling resilient arp after talking to 3Com tech support - didn't need it with our configuration.

--------------From page 79---------------

Enabling/Disabling Resilient ARP Function
After resilient ARP is enabled, the system can ensure there is only one Layer 3 device, and that others are Layer 2 devices.
Perform the following configuration in System View.

Table 75 Enabling/Disabling Resilient ARP Function

Operation - Enable resilient ARP function
command - resilient-arp enable

Operation - Disable resilient ARP function
command - undo resilient-arp enable

By default, resilient ARP function is enabled.
If you are attempting to stop the Switch from transmitting packets, you need to disable all features which may generate packets. By default these are:
?DHCP
?Resilient ARP
?Spanning Tree

--------End of info from page 79 --------

I'm not suggesting you do anything but undo resilient-arp as you may be using DHCP or stp.

Good Luck

 

[jerrycb]

Hi Scottaobe,

Thanks for your reply.

I disabled resilient ARP with command - undo resilient-arp enable and it worked.

Thanks again for your help.
Jerry