# Newbie question on ip\_hash **URL:** \ **Category:** NGINX\ **Created:** [February 5, 2013, 4:39pm UTC](https://www.ruby-forum.com/t/newbie-question-on-ip-hash/229536 "2013-02-05T16:39:04Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [February 5, 2013, 4:39pm UTC](https://www.ruby-forum.com/t/newbie-question-on-ip-hash/229536/1 "2013-02-05T16:39:04Z")
Why does ip\_hash only use the first 3 octects of the IP address? The reason I ask is that we run we servers for a number of schools. Each school is going the be their own subnet, ranging from a /24 to a /20 in size. Since ip\_hash will lump everyone from a /24 in the same hash, it will direct them to the same server, correct? If I am correct above, is there any way to create persistent connections based on the full IPv4 address? – William Brown Core Hosted Application Technical Team and Messaging Team Technology Services, WNYRIC, Erie 1 BOCES Confidentiality Notice: This electronic message and any attachments may contain confidential or privileged information, and is intended only for the individual or entity identified above as the addressee. If you are not the addressee (or the employee or agent responsible to deliver it to the addressee), or if this message has been addressed to you in error, you are hereby notified that you may not copy, forward, disclose or use any part of this message or any attachments. Please notify the sender immediately by return e-mail or telephone and delete this message from your system. ---
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [February 6, 2013, 5:47pm UTC](https://www.ruby-forum.com/t/newbie-question-on-ip-hash/229536/2 "2013-02-06T17:47:57Z")
Hello! On Tue, Feb 05, 2013 at 10:38:35AM -0500, [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Why does ip\_hash only use the first 3 octects of the IP address? > > The reason I ask is that we run we servers for a number of schools. Each > school is going the be their own subnet, ranging from a /24 to a /20 in > size. Since ip\_hash will lump everyone from a /24 in the same hash, it > will direct them to the same server, correct? Yes. The ip\_hash balancing was designed to work with internet services, and use of /24 networks allows it to keep users from migrating between backend servers as they get new IP address on reconnect/reboot (typically from the same /24 network, at least at the time ip\_hash was introduced) while still providing good distribution between backend servers. This probably isn’t very useful nowadays, but this is how it works. > If I am correct above, is there any way to create persistent connections > based on the full IPv4 address? There is a number of 3rd party modules available which do hash calculation based on arbitrary variables, and these may be used if you need a hash based on full client’s IPv4 address (there is $remote\_addr variable). – Maxim D. > **[F5 NGINX: Built for cloud-native apps. Ready for AI traffic.](https://www.f5.com/products/nginx)** > > Deliver modern applications with NGINX. Explore high-performance load balancing, API gateways, and web server solutions trusted by top global enterprises. ---
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [February 6, 2013, 6:00pm UTC](https://www.ruby-forum.com/t/newbie-question-on-ip-hash/229536/3 "2013-02-06T18:00:51Z")
Maxim wrote on 02/06/2013 11:47:22 AM: > The ip\_hash balancing was designed to work with internet services, > and use of /24 networks allows it to keep users from migrating > between backend servers as they get new IP address on > reconnect/reboot (typically from the same /24 network, at least at > the time ip\_hash was introduced) while still providing good > distribution between backend servers. This probably isn’t very > useful nowadays, but this is how it works. Thank you for the explanation. > > If I am correct above, is there any way to create persistent > > connections > > based on the full IPv4 address? > > There is a number of 3rd party modules available which do hash > calculation based on arbitrary variables, and these may be used if > you need a hash based on full client’s IPv4 address (there is > $remote\_addr variable). The backend I am hoping to use nginx for works fine without persistence, I was just thinking it would help with troubleshooting by keeping all of a user’s activity on one server. That way I would have one log to check. I will look into those modules. Confidentiality Notice: This electronic message and any attachments may contain confidential or privileged information, and is intended only for the individual or entity identified above as the addressee. If you are not the addressee (or the employee or agent responsible to deliver it to the addressee), or if this message has been addressed to you in error, you are hereby notified that you may not copy, forward, disclose or use any part of this message or any attachments. Please notify the sender immediately by return e-mail or telephone and delete this message from your system.