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NickJH
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VM DHCP short lease times

Generally I've been getting leases from VM's DHCP servers in the order of 250,000 seconds - the last big one was on 12/12 for 268520 seconds. From yesterday, when the next renewal took place, I got a lease of 1553 seconds - a massive drop and it seems very short - less than 30 minutes. Since then all renewals have been for between 1300 and 1800 seconds. Have you any idea why it has changed and why it is so short now?

 

There is a secondary issue which has been going on for years. When getting a lease it comes from a server in to 10.0.0.0 address space, but the lease message contains an IP in it in the 62.254.35.xx sort of area. When the router tries to renew the lease from this IP it gets rejected, possibly because it is seen as outside the VM network. The router keeps trying to renew the lease until it expires when it broadcasts to 255.255.255.255, gets a lease and it goes round the loop again.

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Superuser
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Re: VM DHCP short lease times

Odd you are getting short DHCP leases. the usual lease is for 7 days. How are you determining the lease times?. Are you monitoring with wireshark?

Are you experiencing any performance issues?

The second issue is quite normal. As a security measure VM's DHCP servers refuse leases whilst the DHCP cycle is in RENEW mode, after the T1 counter is passed (usualy 50% of the lease time). The 10.xxx.xxx.xxx will be your local IP address on the Virgin network which the public WAN address 62.254.35.xxx will be issued to.

Once the T2 counter has been passed (67% of the lease) the Hub will go into REBIND mode where it will request an IP address off any DHCP sever on the network, hence the network broadcast address of 255.255.255.255 which broadcasts to the whole network.

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NickJH
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Re: VM DHCP short lease times

I have the superhub in bridge mode connected to a Linux box behind which is running dnsmasq. Dnsmasq reports the lease times. This is a snippet from the last good renewal:

Dec 12 14:23:45 server dhclient[2712]: DHCPREQUEST on enp2s0 to 62.254.35.61 port 67 (xid=0xab5a451)
Dec 12 14:23:46 server dhclient[2712]: DHCPACK from 82.19.158.1 (xid=0xab5a451)
Dec 12 14:23:48 server dhclient[2712]: bound to 82.19.158.xxx -- renewal in 268520 seconds.
Dec 15 16:59:08 server dhclient[2712]: DHCPREQUEST on enp2s0 to 62.254.35.61 port 67 (xid=0xab5a451)
Dec 15 16:59:09 server dhclient[2712]: DHCPACK from 82.19.158.1 (xid=0xab5a451)
Dec 15 16:59:11 server dhclient[2712]: bound to 82.19.158.xxx -- renewal in 1553 seconds.
Dec 15 17:25:05 server dhclient[2712]: DHCPREQUEST on enp2s0 to 62.254.35.61 port 67 (xid=0xab5a451)
Dec 15 17:25:05 server dhclient[2712]: DHCPACK from 82.19.158.1 (xid=0xab5a451)
Dec 15 17:25:07 server dhclient[2712]: bound to 82.19.158.xxx -- renewal in 1617 seconds.
Dec 15 17:52:04 server dhclient[2712]: DHCPREQUEST on enp2s0 to 62.254.35.61 port 67 (xid=0xab5a451)
Dec 15 17:52:04 server dhclient[2712]: DHCPACK from 82.19.158.1 (xid=0xab5a451)
Dec 15 17:52:06 server dhclient[2712]: bound to 82.19.158.xxx -- renewal in 1708 seconds.
Dec 15 18:20:34 server dhclient[2712]: DHCPREQUEST on enp2s0 to 62.254.35.61 port 67 (xid=0xab5a451)
Dec 15 18:20:34 server dhclient[2712]: DHCPACK from 82.19.158.1 (xid=0xab5a451)
Dec 15 18:20:36 server dhclient[2712]: bound to 82.19.158.xxx -- renewal in 1570 seconds.

I've cut all the subsequent entries, but I've had 89 renewals since 17:00 on 15/12. I don't think it is impacting performance but it is odd.

 

Re the second issue, I understand what is happening, but I don't see why VM don't just put the 10.x.x.x address in their reply. That way it is only accessible from their network avoids the security measure being needed. To me, is the more normal method of operation (to hand out a DHCP reply with a valid DHCP server address). It will also stop the spamming of my logs as each renewal fails..

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NickJH
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Re: VM DHCP short lease times

At 00:20:00 this morning:

Dec 18 00:20:51 server dhclient[2712]: DHCPREQUEST on enp2s0 to 62.254.35.61 port 67 (xid=0xab5a451)
Dec 18 00:20:51 server dhclient[2712]: DHCPACK from 82.19.158.1 (xid=0xab5a451)
Dec 18 00:20:53 server dhclient[2712]: bound to 82.19.158.xxx -- renewal in 260685 seconds.

So it looks like back to normal. Smiley Happy

Presumably VM pushed a fix through?

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