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Nimbostratus

Sep 07, 2023

Remove subnet from NAT pools without any impact

What is the easist way to Remove subnet from NAT pools without any impact

Mohamed_Ahmed_Kansoh
Sep 07, 2023
Hi zztop123 ,

Look ,
you should first see how this pool of NAT IPs used , see if it's used by huge amount of traffic , or by little or isn't used.

if this subnet not used , you can remove it , it will not cause any impact.

but if this subnet is used much in NATing you should remove it , as you maybe impacted by port exhausion so at this case you shouldn't remove it.

So the impact only is with port exhausion not anything else.

Mohamed_Ahmed_Kansoh
MVP
Sep 07, 2023
Hi zztop123 ,

Look ,
you should first see how this pool of NAT IPs used , see if it's used by huge amount of traffic , or by little or isn't used.

if this subnet not used , you can remove it , it will not cause any impact.

but if this subnet is used much in NATing you should remove it , as you maybe impacted by port exhausion so at this case you shouldn't remove it.

So the impact only is with port exhausion not anything else.
- zztop123
  Nimbostratus
  Sep 08, 2023
  Thats right , thats what i was concerned with.If we monitor the use and if its use, and we disable the pool to see the impact ?You think that would be a better idea
  - Mohamed_Ahmed_Kansoh
    MVP
    Sep 08, 2023
    Hi zztop123 ,
    
    Take a packet capture in the server side and see how this pool of NAT ips utilized.
    
    If you saw much traffic converted to source ips from the subnet that you want to remove it here you should be careful fron port exhaustion issue.
    
    If you don't much traffic use ips from the subnet you need to remove it you can delete it.
    
    Look at this article , it explains port exhaustion : https://my.f5.com/manage/s/article/K33355231
    
    So the recommendation is to keep monitor in /var/log/ltm periodically to see if there is port exhaustion or not.
    
    If you found this log even one time , you should rollback and return the removed subnet again in the pool.