Change default TTL value

bkcberry

Hey guys, quick question. I can run the command```
sysctl net.inet.ip.ttl=128

net.inet.ip.ttl=128


to /etc/sysctl.conf and reboot, nothing happens. Anyone know how to make this stick?

johnpoz

you would create it in the gui section for that.

tunables.png_thumb

bkcberry

Awesome, thanks!!

johnpoz

If you don't mind why are you needing to change the ttl - that damn curiosity kat of mine is a PITA ;)

JKnott

If you don't mind why are you needing to change the ttl - that damn curiosity kat of mine is a PITA ;)

I was wondering the same thing.

johnpoz

I saw an issue long time ago 2012 where the dhcp client was setting low ttl of 16 and someone in the EU was unable to get dhcp from their isp.. because it was so many hops away. Had to recompile the dhcp client for them - even filed a bug with freebsd, which they finally fixed in 2014, like 1 month shy of 2 years later ;)

But other than something like that not sure why would need to change the ttl..

Here is the bug I filed - its the only freebsd bug I ever filed ;)
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=170279

But something like that is really only reason why I would think you would have to set that.. So yeah that damn kat keeps meowing at me on what the problem is ;)

JKnott

^^^^
A quick peek with Wireshark shows TTL/Hop Limit of 64 outgoing and various values in the 50s incoming.

johnpoz

Yeah 64 is common default.. 128 is a lot of freaking hops ;) Which is why so curious to why would need to change to 128..

JKnott

@johnpoz:

Yeah 64 is common default.. 128 is a lot of freaking hops ;) Which is why so curious to why would need to change to 128..

Maybe he has a really BIG network. ;)