[sapphireweb]

Linksys - wrt1900ac
Firmware: DD-WRT v3.0-r48432 std (03/01/22)


First, forgive me if this has already been answered, and point me to the link. I have spent 3-hours or so trying to find this. I can't believe I am the only one that has this question.

Where do I find a definition, and valid values for the fields on the Administration -> Sysctl page. (sysctl.asp)

Thank You.

[blkt]

Research each one at a time and it is likely you want to keep all defaults or as-is except disable these two.

net.ipv4.tcp_tw_recycle
net.ipv4.tcp_tw_reuse

nvram show | grep tcp_tw
nvram set net.ipv4.tcp_tw_recycle=0
nvram set net.ipv4.tcp_tw_reuse=0
reboot

[the-joker]

Generally speaking if you want to know what each value is for, on a regular Linux distro you can open the /etc/sysctl.conf in any text editor and read the comments for each option.

If something is not on that file, just google the string Im sure you will have plenty hits.

Unless you know what you're doing I dont recommend messing around with these values.

[the-joker]

Also mind that net.ipv4.tcp_tw_recycle may not be available in all routers, its not in mine and setting it may lead to unknown behavior.

[kernel-panic69]

Both parameters are available on 4MB flash images AFAIK; not sure why it's not available on your device(s).

[blkt]

"Good news tcp recycle will be disabled by default in the next build to address GUI issue."

Starting 44978 changeset 44991 adds new list, then 47246 disables and 47247 blacklists.

Depends kernel version, build installed and configuration generated from previous builds.

You know those who never reset 'nvram show | grep tcp_tw' exists here for good reason.

[the-joker]

This is not just DD-WRT, Red Hat RHEL 8 doesn't have it (last I checked) and probably many others.

Also definetly recommend a nvram reset after such sweeping changes to nvram values are done.

Without actually following the development of DD-WRT closely, for the general populous twice yearly nvram reset wouldn't be a farfetched bad piece of advice.

What we really need is a way to reconfigure the nvram quickly via command line based on settings / nvram strored variable that are hardly going to change, like static leases and other ACL's, security settings and MAC Filter lists etc.

I for one have a human readable config backup to do just this, because setting up from scratch is a pita. I can also easily do diffs between these to see how much has changed nvram side based on twice yearly, pre/post nvram reset.

[blkt]

tcp_tw_recycle removed in 4.12 and yes yearly reconfig is considered especially if major changes occurred.

To go as far to as jump through additional hoops to avoid manual configure from scratch, to each their own.

[the-joker]

Depends, if your specific usage and config you notice or not possible issues because of all the crud left behind. Most people dont notice anything until they try to do something else.

Just look trough reports on build threads, where ppl report no issues and indeed there are, I found severe bugs not long ago 3 builds back and on build reports threads everyone was happy, just may not be immediately obvious due to their config/usage or because in all honesty I doubt anything beyond works/dont work is actually tested.
Doesnt mean those issues were caused by nvram values alone, but there we are.

But yea, to each their own, Im not losing sleep over what others do or dont.

[kernel-panic69]

[the-joker]

My results, indeed I reset nvram recently 4 build ago

No recycle.

uname -a
Linux Nexus 4.4.302 #5645 SMP Wed Mar 30 21:22:21 +07 2022 armv7l DD-WRT

[ho1Aetoo]

and it is not present in the kernel either?

[the-joker]

kernel side it exists as 0

[kernel-panic69]

An image of the output of nvram show | grep tcp would've sufficed instead of an animated gif that I cannot really focus on enough to read clearly, thanks.

[Cartel]

My router shows net.ipv4.tcp_tw_recycle=1 with the nvram show | grep tcp_tw command but the Sysctl page doesnt list it, only tcp_tw_reuse which is 1

Firmware: DD-WRT v3.0-r58819 std