2 Degrees ISP/DHCP issue - constantly renewing every 2.5 mins

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Ristretto63

2 posts

Wannabe Geek

#319429 24-Apr-2025 13:31

Hi Team

Our business router is constantly renewing IP address every 2.5 mins.

ER706W-4G - Omada 4G+ Cat6 AX3000 Gigabit VPN Router

1 2025-04-24 13:26:44 DHCP Client NOTICE

WAN2: DHCP client renewing IP succeeded. (IP-Address=203.86.192.199, Mask=255.255.255.240, Gateway=203.86.192.193)

2 2025-04-24 13:26:41 DHCP Client NOTICE

WAN2: DHCP client lease expired. Began renewing the lease.

3 2025-04-24 13:24:14 DHCP Client NOTICE

WAN2: DHCP client renewing IP succeeded. (IP-Address=203.86.192.199, Mask=255.255.255.240, Gateway=203.86.192.193) 4 2025-04-24 13:24:11 DHCP Client NOTICE WAN2: DHCP client lease expired. Began renewing the lease.

I sent email to 2 Degrees as I believed that it was an issue with their DHCP server

Their response was:

Thank you for your email, I'm sorry to hear there's been ongoing issues,

Our assurance team has investigated and advised the issue does not appear to be on our side.

They have recommended you refer to the vendor regarding your BYOD,

They have recommended checking your DHCP settings, checking for any potential Rogue DHCP server on the network,

Checking physically damaged ports/cables. Ensuring the Network adaptor drivers are up to date,

checking for Multi-DNS issue if applicable, checking for Lease time settings and Firewall issues.
These potential reasons why the issue may be occurring and they are beyond our scope.
Please let me know if you have any further question by replying to this email,

Does anyone else have similar issues and how have you resolved them.

Cheers

MaxineN

Max
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#3367128 24-Apr-2025 14:01

Unless I'm missing something, your IP address hasn't changed in those logs.

They do have a 5 minute lease time, so renewing half way makes sense right? The client needs to let the server know "hey I'm still here, please renew my lease time."

What is the actual fault that is being experienced?

Ramblings from a mysterious lady who's into tech. Warning I may often create zingers.

Ristretto63

2 posts

Wannabe Geek

#3367137 24-Apr-2025 14:15

No our IP address hasn't changed it is still having the same one reissued. I'm just concerned that an ISP would have a lease period of 5 minutes, and forcing renewal at 1/2 that time period.

I know that we have a STATIC IP on our contract/connection, and wondering whether we shouldn't apply static to the router instead of dynamic address.

Why would they send me a reply to investigate rogue DHCP servers on our network when they know what their lease period is.... that is, if it is actually 5 minutes.

And surely there is an interruption to our internet service every time the lease renews??

djtOtago

1149 posts

Uber Geek

#3367139 24-Apr-2025 14:20

I'm with Slingshot which is part of the 2Degrees family and my router renews its lease about every 2.5 minutes as well. The new lease is for 300 seconds.
My IP address never actually changes. Don't really notice anything other than lots of log entries. As far as I can see this is normal behaviour.

MaxineN

Max
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#3367141 24-Apr-2025 14:21

The response you've gotten looks like a generic boiler plate one, and the question (this doesn't look like a fault) that was asked was misunderstood.

Generally no there would be no disruption unless something does change, which from those logs... looks like nothing has changed.

I'll refer back to the question that still needs to be answered, what is the actual fault that is being experienced? Is there disruption in services? If you were to download something does it get interrupted? Are you getting alerts saying WAN2 is down and there is no connectivity?

If we answered none to the above then no there is no fault and DHCP is just doing what DHCP should be doing, which again from the logs... it is doing what it is supposed to do.

Ramblings from a mysterious lady who's into tech. Warning I may often create zingers.

djtOtago

1149 posts

Uber Geek

#3367142 24-Apr-2025 14:36

Ristretto63:

<snip />

And surely there is an interruption to our internet service every time the lease renews??

No interruption unless the IP address changes.
I have SSH connection / tunnels and RDP sessions running for hours, sometimes days, with out a blip (Technical term)

I don't have a static IP address, but my IP address almost never changes. I've only had 3 IP address changes in the last 10 Years with Slingshot.

saf

157 posts

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#3367143 24-Apr-2025 14:47

For a 5 minute DHCP lease, a renew at the ~2.5 minute mark is absolutely normal, and a lease renew at half of the expiry time is expected, as per RFC 2131.

On renews, routers should then wait for a binding as below (from the RFC):

In both RENEWING and REBINDING states, if the client receives no

response to its DHCPREQUEST message, the client SHOULD wait one-half

of the remaining time until T2 (in RENEWING state) and one-half of

the remaining lease time (in REBINDING state), down to a minimum of

60 seconds, before retransmitting the DHCPREQUEST message.

A normal DHCP renew should not cause any impact, and if it's not - then there's nothing wrong with your service, it's doing exactly as it should as per RFC. This is good, what you don't want is your lease getting to the expiry time which would cause an interruption, as it would need to request a whole new lease, rather than a renew.

If however you're getting an outage every ~2.5 minutes at renew time, that's a different story. If so, my first port of call would be ensuring your device firmware/software is all up to date in case a buggy version was released which doesn't obey the above mentioned RFC statement about wait times from a renew or rebind request.

My views are as unique as a unicorn riding a unicycle. They do not reflect the opinions of my employer, my cat, or the sentient coffee machine in the break room.

RunningMan

8955 posts

Uber Geek

#3367149 24-Apr-2025 15:25

Ristretto63:And surely there is an interruption to our internet service every time the lease renews??

Should be no interruption at all. It's perfectly normal