changing SNAT pool every week by iRule

Here's just ONE idea:

when RULE_INIT {
set static::SNAT_0 "10.80.0.100"
set static::SNAT_1 "10.80.0.101"
set static::SNAT_2 "10.80.0.102"
set static::SNAT_3 "10.80.0.103"
}
when CLIENT_ACCEPTED {
 find SNAT pool
eval "set snat_id \$static::SNAT_[expr { [clock format [clock seconds] -format %W] %4 }]"
log local0. $snat_id
snat $snat_id 
}

This would cycle a list of 4 snat IPs/pools (%4 - modulus 4 in the equation) per week.

Hi,

 

Thanks for your reply.

 

 

Can i change using HTTP_REQUEST instead of CLIENT_ACCEPTED?

 

Because this iRules will be a NATing a server IP go internet with thru HTTP port?

 

Can check with you, if i would like to change SNAT to snatpool, is it feasible?

 

 

Thanks.

 

Danial

 

On the first question, yes you can use the HTTP_REQUEST event, but I don't really think you need to. All TCP/UDP client connections will trigger the CLIENT_ACCEPTED event, regardless of the higher level protocol.

 

 

On the second question, yes you can definitely change "snat" to "snatpool" and modify the static variables in RULE_INIT to be SNAT pool names.

 

Hi Kevin,

 

 

Thanks for your reply.

 

Noted for your 2 question answer.

 

Is it iRules will run the new snatpool for every Monday?

 

Then, for Tuesday till Sunday, the snatpool will stick to the same snatpool?

 

For Ex:

 

1st July - Monday, let say it trigger the iRule to run. Result: server A using using snatpool A

 

Will the server A still using snatpool A from 2nd July to 6th July?

 

 

I am thinking possible we can write the status into a text file to keep track the last activity?

 

 

PS: Sorry, i am a newbie in writting an iRule.

 

 

Thanks.

 

Danial

 

 

 

 

I didn't ~exactly write it to your specifications. ;) The above iRule is based on weeks of the year (1-52). The "%W" means the week of the year starting on Monday, so every Monday the value would cycle (next week). We'll take the modulus 4 of that number to get a value between 0 and 3. Example:

 

 

Week = Value

 

1 = 1

 

2 = 2

 

3 = 3

 

4 = 0

 

5 = 1

 

6 = 2

 

...

 

50 = 2

 

51 = 3

 

52 = 0

 

 

A few additional points:

 

 

1. This runs on every client request (CLIENT_ACCEPTED or HTTP_REQUEST). Also consider that at midnight on Sunday, should someone be in an active session, the snat/snatpool would change. I'm not 100% certain what the affect of that would be mid-session.

 

 

2. This is a VIP-global setting, so when you say "server A using using snatpool A", understand that the snat/snatpool is applied to all servers in the pool.

 

 

3. It's still possible to get it to rotate on a Wednesday, but would require a little extra work.

 

 

4. Because this calculation is triggered on every client request, you may not want to log all of that.

Posted By Kevin Stewart on 07/03/2013 05:29 AM

 

I didn't ~exactly write it to your specifications. ;) The above iRule is based on weeks of the year (1-52). The "%W" means the week of the year starting on Monday, so every Monday the value would cycle (next week). We'll take the modulus 4 of that number to get a value between 0 and 3. Example:

 

 

Week = Value

 

1 = 1

 

2 = 2

 

3 = 3

 

4 = 0

 

5 = 1

 

6 = 2

 

...

 

50 = 2

 

51 = 3

 

52 = 0

 

 

A few additional points:

 

 

1. This runs on every client request (CLIENT_ACCEPTED or HTTP_REQUEST). Also consider that at midnight on Sunday, should someone be in an active session, the snat/snatpool would change. I'm not 100% certain what the affect of that would be mid-session.

 

 

2. This is a VIP-global setting, so when you say "server A using using snatpool A", understand that the snat/snatpool is applied to all servers in the pool.

 

 

3. It's still possible to get it to rotate on a Wednesday, but would require a little extra work.

 

 

4. Because this calculation is triggered on every client request, you may not want to log all of that.

 

Hi Kevin,

 

 

Thanks for your reply.

 

I roughly have some idea about this.

 

I had wrote a iRule myself but i am not sure is workable or not? Perhaps you can help me to review?

 

It means, snatpool will take effect on 1 week - Monday, with NAT_A_pool, but i am not sure tuesday, wednesday... until next week - Monday will stick to NAT_A_pool

 

 

if {[IP::client_addr [IP::client_addr] equals 192.168.1.1] {

 

 

set FixDate "Monday"

 

set TodayWeekDay [split [clock format [clock seconds] -format {%A}]

 

set CurDay [split [clock format [clock seconds] -format {%e}]

 

set CurTime [clock seconds]

 

set FixTime [clock scan {12:00}]

 

set x [CurDay - 1]

 

 

if {(TodayWeekDay equals "$FixDate") && (CurTime equals FixTime)} {

 

if {(x equals 0 >= 6) {

 

snatpool NAT_A_pool

 

pool Default_A_GW

 

 

elseif {(x equals 7 >= 13) {

 

snatpool NAT_B_pool

 

pool Default_B_GW

 

 

elseif {(x equals 14 >= 20) {

 

snatpool NAT_A_pool

 

pool Default_A_GW

 

 

else

 

snatpool NAT_B_pool

 

pool Default_B_GW

 

else {

 

if {(x equals 0 >= 6) {

 

snatpool NAT_A_pool

 

pool Default_A_GW

 

 

elseif {(x equals 7 >= 13) {

 

snatpool NAT_B_pool

 

pool Default_B_GW

 

 

elseif {(x equals 14 >= 20) {

 

snatpool NAT_A_pool

 

pool Default_A_GW

 

 

else

 

snatpool NAT_B_pool

 

pool Default_B_GW

 

}

 

}

 

 

 

The example I gave would change the week number every Monday, and subsequently the snat/snatpool. So from Monday to Sunday the week and snat/snatpool would be the same. You can also change the pool by adding pool names as separate static variables, or put all of it into data groups.