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WAN DHCP Lease Time and Encapsulation Method

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13 REPLIES 13
bassballs
Conversation Starter

Hi

 

I'm currently using a 3rd party router (Netgear D7000v2) - the WAN DHCP Lease time is only 15mins - surely this is too short? Netgear states that this is what is picked up on initial setup. However from what I remember the HG633 router's release time was set at 1 week.

 

I'm currently on FTTC  - and setup as not needing a username and password to sign in. However when the Netgear was setting up it selected as beiing automatically PPPoE and asked for a username and password. 

 

Is it possible to setup as PPPoE and where would I get the username/password (I tried the one for when I was on ADSL but it didn't work).

 

 

Keith

Bassballs
KeithFrench
Community Star

No router has control over the WAN DHCP server, that is under the control of the ISP or maybe even BT. All you can do is alter some parameters that the router as a DHCP client can send within its DHCP request. For example "DHCP Option 60" which is normally set to identify the router name & firmware version. 

Keith
I am not employed by TalkTalk, I'm just a customer. If my post has fixed the issue, please mark it as the Best Answer.
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bassballs
Conversation Starter

Thank you Keith for your reply

 

What would I enter for these options?

 

Keith

Bassballs
KeithFrench
Community Star

Hi @bassballs

 

Try this:-

 

Typical DHCP.png

Keith
I am not employed by TalkTalk, I'm just a customer. If my post has fixed the issue, please mark it as the Best Answer.
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KeithFrench
Community Star

I have been looking into this further & it seems to only happen to people using 3rd party routers having certain chipsets. This is from one post, but I have no way of knowing if this is correct:-

 

Just searched the TT forums and in one thread it was said that if you have a Broadcom chipset the lease should be permanent but with Lantiq and others it may be 15 minutes. someone else suggested it could be that no Option 60 is set and that is why. I have a VMG3925 router which is a Broadcom unit so that should according to the comments I read give me a permanent lease. I dont get any obvious drops of the line or IP changes. It was suggested that the TT Super Router passes Option 60 to TT which then gives a permanent lease. If this is true it's a way of TT making it difficult for non TT supplied routers to be used. TT uses IPOE btw not PPPOE.

 

I have also seen from other people such as @charlesb224 he does not need to enter anything in the DHCP Option 60 field of his Asus RT-N66U. See his posts in this thread:-

 

https://community.talktalk.co.uk/t5/Fibre-Broadband/DHCP-lease-from-TalkTalk-only-15-minutes/m-p/176...

 

 

 

 

 

Keith
I am not employed by TalkTalk, I'm just a customer. If my post has fixed the issue, please mark it as the Best Answer.
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charlesb224
Wise Owl

@KeithFrench @bassballs

 

The official statement on lease times is that it is 15mins for ALL customers, regardless of router

see here: I-noticed-today-that-my-VDSL-connection-has-only-15-minute-DHCP

 

Only TT & Sky use DHCP.  All other ISPs use PPP which has a constant keepalive method of connection, so 15 minutes is quite reasonable.  If your router can't keep up, then your router is at fault - my 3rd party router has been flawless for >2 years with 2 separate modems (HG635 and more recently a W8980)

 

Edit: just saw you're using a netgear...  they recently rushed out lots of firmware to fix some major security issues: I wouldn't buy a netgear again - although it was the very first router I ever purchased 14 years ago :cooldude:

KeithFrench
Community Star

Thanks for that @charlesb224. I think there is some slight confusion though on the part of TalkTalk with this. DHCP is obviously the protocol that deals with IP address allocation, it has nothing to do with PPP. I think what they mean is that PPPoE has more keep-alives than IPoE.

Keith
I am not employed by TalkTalk, I'm just a customer. If my post has fixed the issue, please mark it as the Best Answer.
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KeithFrench
Community Star

Hi @bassballs

 

I have been thinking this through some more & whilst I don't have a direct answer this may clear up (I hope) some confusion.

 

First off I totally agree with @charlesb224 that the DHCP Option 60 setting is not important here at all. Some of the information I have provided below is taken from Charles previous posts (full credit to him), he has plenty of experience with 3rd party routers used on broadband, I do have an extensive knowledge of routers but only those used in the commercial arena, not on broadband links.

 

So this is it:-

 

First off check the routers WAN or Internet configuration. The Connection Type field in this section of the configuration should be set to IPoE with TalkTalk, not PPPoE.

 

This only affects customers using some 3rd party routers and it might be down to the chipset manufacturer used by that router.

 

Some people think that if you if you have a Broadcom chipset the lease should be permanent but with Lantiq and with others, it may be 15 minutes.

 

That paragraph above is also not true, because the DHCP client (router in this case) has no control over the lease, all they can do is request its extension. That said, perhaps some chipsets do not request a link extension or are wrongly configured as PPPoE.

 

Consider what happens when the DHCP lease is 50% expired 

 

When a DHCP client (broadband router in this case) is assigned a WAN IP address from the DHCP server on the network, it is also assigned a lease time (typically 15 minutes in this case – to conserve IPv4 addresses). At this point, the client is classed as being bound to the allocated IP address.

 

When this lease time is 50% expired after 7.5 minutes, the router (DHCP client) sends a DHCP Request to the server to extend the lease. At this point, technically the client (broadband router) is classed as renewing its IP address. Assuming the server that issued the lease originally can still be contacted, then it will respond to this request, returning a DHCP Ack to the client, renewing the lease & rebinding the client to the same IP address.

 

Therefore so long as the WAN link (virtual circuit) remains connected, the router should retain its existing IP address.

 

 

 

The most likely case I think is that the lease extension request is not being issued by the router (this may be down to the chipsets) and hence the lease is not renewed. Once the lease has expired the virtual circuit (WAN link) is taken down. The router then has to request an address again, but this time is allocated a different one. This might be down to there not being so many keep-alives within IPoE compared to PPPoE, but this is nothing more than a guess.

Keith
I am not employed by TalkTalk, I'm just a customer. If my post has fixed the issue, please mark it as the Best Answer.
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bassballs
Conversation Starter

Hi

 

Sorry this is late - but thanks everyone for your replies...a lot to take in there lol.

 

I'm currently back on the talktalk router as my speed has dropped slightly - si I have it plugged into the test socket in the hope that the DLM will increase it agai.

 

Keith

Bassballs
px03afk
Wizz Kid

I know this thread hasn't been used for a while but as I've just  noticed the same thing I thought I might ask TT why they have such a short lease.  I would expect that the majority of connections to TT are from modems/routers which are permanently connected and if that is the case there are a huge number of systems asking for lease renewal every 7 minutes or so and getting back the same IP address.  If this was a dial-up service I could understand the benefit of having short leases but with virtually permanent connections it makes no sense.  I don't know if anyone else has my problem but every so often my router fails to get a new address and eventually the connection breaks.

 

Howerver, back to my main point, even a 1 hour lease would ease the renewal traffic by 25% and a 2 hour lease by 50%.  So what is the risk of an IP address being unavailable for two hours?

KeithFrench
Community Star

This is nothing to do with TalkTalk, but is all down to some 3rd party routers not being configured correctly. When the lease gets to 50% duration expired, the 3rd party router should request an extension to the lease, which would automatically be granted.

Keith
I am not employed by TalkTalk, I'm just a customer. If my post has fixed the issue, please mark it as the Best Answer.
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px03afk
Wizz Kid

Sorry but you seem to have missed my main point about why the leases are so short.  Yes, my router may be at fault for not renewing it correctly but if it was longer it would be less of a problem, coupled with the fact that a router which might be slow in renewing would have more time to do the renewal.

KeithFrench
Community Star

No I didn't miss the point, the DHCP servers are BT's, TalkTalk do not have control over them. Why doesn't this happen on TalkTalk routers then?

Keith
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charlesb224
Wise Owl

As @KeithFrench mentions... this is an issue with 3rd party routers.  Never had an issue with my own 3rd party router in 5 years with TalkTalks 15 minute lease renewal time.

 

On a side note, the reason that BT and others don't have this 'issue' is that they use PPP as a connection method, which is actually a constant level of traffic every few seconds to keep the PPP session 'alive'.  DHCP every 15 minutes is miniscule in comparison.

 

TalkTalks method of IP Allocation via DHCP is actually very efficient.