I have a stack of four switches Netgear GS700TS interconnected loop for some redundancy in case of loss of one of the switches. Under these conditions the Spanning Tree Protocol must be enabled to handle loops and thus multiple paths between two points. Unfortunately this has an important effect on the speed of acquiring connection information for a DHCP client, time to obtain an IP is on the order of 35 s, which is quite annoying in the long run.
Why this delay? When a client connects to a port of the stack, looking for a DHCP server is normally performed and the time to obtain an IP is about 4-5 s. The problem here is that the spanning tree enabled on the switch starts by blocking any communication on the port before checking that there is no loop back. This verification usually requires a few seconds but the DHCP client's request was blocked passes timeout after about thirty seconds before being returned. At this time the switch was able to verify that there was no loop behind the door and let go so demand, then being given a response within 5 s, causing a total delay of approximately 35s.
To remedy this, simply go into the management interface of the stack in Switch> Advanced> Spanning Tree and click on a port. It must then pass the Fast Link Enabled and select All Ports of the Stack to apply the setting to the entire stack.
Spanning Tree Options
This option requests that the switch not to block communications port while checking the presence or absence of loops (where a loop is detected then the switch would cut the connection), do not the first blocking search for DHCP.
Tags: DHCP , Spanning Tree , Switch
