Can't get Vlan to accept DHCP address

[HunterHage]

In order for the answer below to work, in this setup I had to stop using the Gigabit port entirely and just use FastEthernet0/1 as the connection to the ATT.

~~~

Hello, I will be honest that I am very new to this. Luckily I am trying to do something simple.

I have two devices that are unique here an ATT Pace 5268AC Modem Router that is responsible for Internet Access and DHCP, then a Cisco Catalyst 3560 that will be responsible for routing our home devices through one port that I can mirror and monitor.

I have a Vlan 50 setup to connect FastEthernet0/1 - 0/12 and Gigabit0/1 together and Vlan 50 is set to acquire its' IP address from the ATT router's DHCP service. I cannot set the Vlan's IP manually because the ATT router cannot find anything that does not connect with DHCP. With this setup normally I can get an IP from ATT for the Vlan50 and all works good thereafter; however the ATT router does misbehave and it has to be restarted. When it does get restarted the switch can no longer connect to the ATT router. Or when I restart the 3560 it does not seek a new DHCP assignment. This causes problems cause I need to perform some sort of ritual that can take anywhere from 10 minutes to three hours to get the 3560 to get a new DHCP assignment from the ATT router.

Ultimately I need to know how to improve this setup to have better reliability in retrieving an IP from DHCP for Vlan50. Or if there is a better method of accomplishing this.

Here is the configuration for the 3560, I am connected to it via console and telnet.

Building configuration...

Current configuration : 1872 bytes
!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CS0
!
boot-start-marker
boot-end-marker
!
enable secret 5 
enable password 
!
no aaa new-model
system mtu routing 1500
ip subnet-zero
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
!
!
!
interface FastEthernet0/1
switchport access vlan 50

!

!

interface FastEthernet0/12
switchport access vlan 50
!
interface FastEthernet0/13
no switchport
ip address 192.168.10.15 255.255.255.0
!

!
interface FastEthernet0/23
no switchport
ip address dhcp
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
switchport access vlan 50
!
interface GigabitEthernet0/2
!
interface Vlan1
no ip address
shutdown
!
interface Vlan50
ip address dhcp
!
ip classless
ip http server
ip http secure-server
!
!
!
control-plane
!
!
line con 0
line vty 0 4
password 
login
line vty 5 15
password 
login
!
end

Any help is appreciated, thank you.

[HunterHage]

This is what the console output looks like when I DO get an IP, normally after unplugging the cabel from one port and into another on the same Vlan. Normally this is my output but without the DHCP message.

~
*Mar 1 00:45:19.746: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
*Mar 1 00:45:19.746: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan50, changed state to down
*Mar 1 00:45:20.744: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down
*Mar 1 00:45:24.091: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
*Mar 1 00:45:25.097: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
*Mar 1 00:45:53.115: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan50, changed state to upInterface Vlan50 assigned DHCP address 192.168.50.21, mask 255.255.255.0

[paul driver · Accepted solution]

Hello

Could be the port is taking to long to go into a stp forwarding state, apply the following

interface FastEthernet0/23
no switchport
ip address dhcp
switchport host

no int vlan 50 <-- not required as the same subnet is being used so you can just use L2 vlan on the access ports in vlan 50

Why do you need a dhcp server when you already have the ISP providing this function.

res
Paul