PC not getting IP automatically(DHCP)

[shyamradhe]

Hello all 

I am facing a very strange issue in my network envoirment

1- I have 1 WAN router from which 1 switch is connected then from that switch 2nd switch is connected(cascading)

2-I have configured Router on stick for VLAN 1- Wired, VLAN-50- WiFi, also configured 2 DHCP pools on router for WiFi and LAN.

All is working fine.till now.

3- now I connected one more switch(3rd) in same way to switch-2.

I can reach the switch(VLAN 1) ip, even from that 3rd switch i can ping to all other VLANs IP.

but when I connect my desktop, it is not getting IP from dhcp. only when i put static IP on it then only i can access internet.

all other configs(trunk, switchport mode etc) are same as other switch...

Please any one can tell what cause may be in this type of issue..??????

[Milos Megis]

Hi,
do you have configured PORTFAST on port where you connect PC.

Because spanning tree by default block port for 30 seconds (listening and learning phase). And DHCP request timed out during this period.

I am not sure but I think that this is your problem.

[shyamradhe]

Yes Milos portfast is configured...

[paul driver]

Hello

Make sure your access switch(s) have ip routing disabled (no ip routing) also all necessary vlans are allowed across the trunks, and your have the L2 vlans are propagated in the vtp database to all switches

Res
Paul

[shyamradhe]

Hi Paul 

Thanks For Reply.

I think all vlan are allowed because when i put static IP then it is reacahable to all vlan IPs.

What i did is .. just make the uplink ports AS trunk make that switch as VTP client..

VLANs are also populated when i run "show vlan"..

"is this also depends on SFP modules ?  because I am not sure that is this uplink port(SFP & Fiber) is single mode or Multi mode, may this cause can conflict ?"