What does the 'ip-netmask' mean?

[ccowe2005]

Hello,

I am trying to configure sticky on an ACE 4710 and don't understand what the netmask part of the sticky ip-netmask netmask address {source | destination | both } name command.

Some examples use 255.255.255.255 and others use 255.255.255.0 but I don't know what the significance is or what it does?

I am going to configure for both source IP and destination IP (both).

I would appreciate some help on this because the online documentation seems to be very limited.

Thanks.

Catherine

[rhgtyink]

Hi Catherine,

I would expect the following behavior, using 255.255.255.255 would create a sticky entry on the table per full source + destination IP if you use 'both'.

The subnet 255.255.255.0 would create an entry of the 'network' + destination IP when used with both.

This would cause a complete /24 network to be balanced to the same session as the first user from that range.

It saves on entries in the sticky table, but is less likely to give a good 'balance' over your serverfarm.

As said the documentation is limited, and I haven't tested this.

If you have a test/lab environment just try it and use the 'show sticky database' command to verify what it does.

[ajayku2]

Hi Catherine,

the ip-netmask will create sticky entries in the sticky table, using the source address of the client, but ONLY for the part matching the ip-netmask.

if the ip-netmask is 255.255.255.255 it will create unique entries for every client.

Also this is good to know:

netmask

Network mask that the ACE applies to the IP address. Enter a network mask in dotted-decimal notation (for example, 255.255.255.0). Note (ACE module only) If you configure a network mask other than 255.255.255.255 (/32), the ACE may populate the sticky entries only on one of its two network processors which may reduce the number of available sticky entries by 50 percent. This reduction in resources can cause problems when heavy sticky use occurs on the ACE.

It is well explained in the following discussion:

https://supportforums.cisco.com/thread/133326

hope that helps.

Ajay Kumar