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Registered: ‎08-04-2016

Howto delay DHCP responses?

[ Edited ]

* My Sophos Guard is de primary gateway (192.168.0.254) and this is a VM.

*¨My UBNT gateway is a fallback (backup) internet connection (192.168.0.1) and this is hardware.

I  have basically two gateways 192.168.0.254 and 192.168.0.1.

 

When I'm using 192.168.0.254 (prime GW) ; I want to use dns servers 192.168.0.4/192.168.0.5 (which are my domain controllers and also dns and dhcp servers). All these systems are VM's.

 

Sometimes with a power outage the VM's don't come up correctly or issues with the virtualization stack for some reason, at that point 192.168.0.254/.4.5 are not reachable and I want  basic internet services assumed by 192.168.0.1

 

I was either thinking in getting in the scope options 3 dns servers and 2 default gateways.If I remember correctly the next one is chosen if the first one doesn't respond.

 

Or Maybe I can accomplish this, where the second dhcp server (UBNT gateway) responds later than the others..

 

  

Thanks,


Tim

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Re: Howto delay DHCP responses?

Are you using a USG as the DHCP server or is it the backup? You need to provide some more details.

You shouldnt have 2 DHCP servers on the same network as thats just madness but i assume thats where your problem is.

Provide some more details on the networking and maybe we can provide answers.
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New Member
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Registered: ‎08-04-2016

Re: Howto delay DHCP responses?

updated the request to make it more clear

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Re: Howto delay DHCP responses?

Two DHCP servers in one network is not a best practice, what you want is impossible to filter DHCP request based on timing. If you want redundant Internet the both devices should act as one gateway together (VRRP/HSRP) or you have one USG with 2 WAN ports.

 

Per vlan there should only one DHCP server active, and not two. As also mentioned by the other poster.

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Re: Howto delay DHCP responses?

It can be OK to have two DHCP servers for redundancy purposes (with proper considerations taken for that situation), but not where they're assigning different gateways, multiple active DHCP servers is not the way to address that. 

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Re: Howto delay DHCP responses?


Some of the DHCP servers included with various router software support the ability to add a delay to DHCP responses. This allows you to setup your Windows/Linux server based DHCP servers as primary, with the router based DHCP server assigning addresses only if the Windows/Linux servers don't respond within the router DHCP server delay interval. Basically, the router based DHCP server responses are ignored by the requesting devices since the Windows/Linux based servers are authoritative, up and operational. When the Windows/Linux based servers are down and don't respond, the requesting devices use the delayed responses from the router based DHCP server. This is a good last resort fall-back that ensures network devices can continue to function during a Windows/Linux server down event, while not having to divide the subnet into multiple scopes.

I'm trying to determine if the USG based DHCP server also supports the ability to delay it's responses.
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