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Re: DHCP disconnects in VLAN

Occasional Contributor

DHCP disconnects in VLAN

Hi all,

I have a HP 1910 configured with 3 vlans. One of them has dhcp-relay enabled.

DHCP-Service and DHCP-Snooping are globally enabled. All fine so far.

The problem is, if I reboot the DHCP-Server (Windows 2012) the clients (Win + Linux) on this vlan will loose their IP and the clients stay disconnected until the next reboot or network-restart.

I found some issues, that the Windows-DHCP could cause such behaviour, but I have no solution. Perhaps it's a misconfiguration on my side.

Any ideas?

Respected Contributor

Re: DHCP disconnects in VLAN

My idea is that once the switch notices that the DHCP server is gone, it clears its dhcp snooping table. 
What triggers this behavior?  The DHCP service being shut down orderly, or the interface where DHCP server was on going down?

Occasional Contributor

Re: DHCP disconnects in VLAN

are there further configurations/settings required?

under dhcp snooping all interface states are "untrusted"

option 82 support = disabled

option 82 strategy = replace

should I change this for all vlan-ports?

Esteemed Contributor

Re: DHCP disconnects in VLAN

DHCP Snooping is used to protect against rogue DHCP servers. So if your DHCP server is not trusted then it will get blocked. I would recommend disabling DHCP Snooping. It is really only needed if you have a problem with people connecting additional DHCP servers to your network.