ATT Fiber aggressive dhcp

michmoor

Hey everrone,
Trying to see what is normal or abnormal with my internet connection. I have ATT Fiber.
Do your WAN interfaces renew every 5 minutes?
What brought me to look into this was that there was a reddit post about some Unifi eqipment stating in the logs that their internet connection is poor. Someone mentioned in the comments that this is a ATT Fiber being weird with how they do Here it is https://www.reddit.com/r/Ubiquiti/comments/1b2sm20/wtf_is_going_on_here/

So i look at my syslog and search for "dhclient" and holy smokes....every 5 minutes there is a renwal. Is this normal for those who got ATT fiber?

dont want to give away my IP but here is a snippet from the logs

johnpoz

@michmoor what device do you have?

https://forums.att.com/conversations/att-fiber-equipment/5-minute-dhcp-lease-on-wan-side/60830cd3a31fd9684f2897bb

If your bridging thru looks like you can configure it.. Do you have the BGW ont?

Looks like you can adjust that when you setup your passthru - and it defaults to 10min lease - so yeah 300 second renew would be what you would see.

michmoor

@johnpoz
Forgive me john im not great on describing things..
I am running a 6100 with a port on the 6100 is connected to the BGW210-700. Thats connected to the ONT on the side of my house and off to the internet.
I did set up passthrough so the pfsense gets a public IP. Other than that nothing special here.

johnpoz

@michmoor so read the thread, looks like when you setup passthru you can adjust the lease time.. Change it from the default 10 minutes..

michmoor

@johnpoz
Yep i changed it from the default 10m to 1 day.
I see the passthrough DHCP Lease and its set to 10 minutes which is higher than the 300 seconds yet pfsense is still doing 5 minute renewals. Weird but lets see how this goes.

michmoor

@johnpoz
Ok.......yep that would solve the mystery. Learned something new every day.

https://www.linkedin.com/pulse/deep-dive-dhcp-lease-time-client-behavior-lasya-gayathri-muramalla-yohhc/

"The client typically sends the DHCP Request when half (50%) of the lease time has elapsed. If it receives the DHCP ACK (acknowledgment), it retains the IP address.
If the client receives DHCP NAK, It comes to the initial stage and performs DORA process "

half of 10 is 5 hence every 300 seconds renewal.

michmoor

already looks better.

Thanks @johnpoz

johnpoz

@michmoor said in ATT Fiber aggressive dhcp:

10 minutes which is higher than the 300 seconds

renew on a lease is 50% of value - so yes a 10 min lease would = a 5 minute renew time.. 24 hours would be every 12 hours.

edit: do the math 43230 is like 12.008 hours ;)

stephenw10

I wouldn't actually expect any problems with a short lease like that though. Renewing it shouldn't cause any interruption.

johnpoz

@stephenw10 yeah it can work - but for one it would be flooding his syslog server, and 2nd for what valid reason would you want such a short lease..

lets do the math, every 5 minutes log to syslog.. Or every 12 hours..

so in 24 hours we would have 2, vs 288 ;), 1 week we have 14 vs 2016.. 2k junk entries in my syslog = why?

Why would the ISP want their clients renewing dhcp every 5 minutes... That just seems insane.. Lets say I have 100k users.. That is lot of renewals for zero point.. Unless they over over booked, and not all their users can be on at the same time?? Because they don't have enough IPs to hand out?