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LAN Switching/Trunking issue

guitar_dave
guitar_dave asked
on
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Last Modified: 2012-05-06
I'm picking up slack while the network engineer is away on vacation, I'm new here and unfamiliar with this network.  Hosts are not getting leases from DHCP server when patched into a Cisco 2960 switch, instead they'll get the 169.254.190.178...This switch is uplinked via G0/1 to FA0/13 a Cisco 3560 switch which appears to already be configured for trunking.  Anyone care to help me troubleshoot this?

2960-G0/1:
interface GigabitEthernet0/1
 description Uplink
 switchport trunk native vlan 1001
 switchport mode dynamic desirable
 srr-queue bandwidth share 10 10 60 20
 queue-set 2
 priority-queue out
 mls qos trust cos
 auto qos voip trust

3560-FA0/13
interface FastEthernet0/13
 switchport access vlan dynamic
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 1001
 switchport mode trunk
 switchport voice vlan 151
 switchport port-security maximum 3
 switchport port-security violation restrict
 srr-queue bandwidth share 10 10 60 20
 priority-queue out
 mls qos trust cos
 auto qos voip trust
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Top Expert 2009

Commented:
Is the DHCP server in the same VLAN as the PC's?  If not, double check the layer3 VLAN interface (assuming on the 3560) has the "ip helper-address <dhcp server ip>" command on it.  Also double check the DHCP scope exists and is active.

Author

Commented:
The DHCP server is on a separate "Server" VLAN, but the ip helper address is configured on that VLAN's interface.  The DHCP scope exists and is active.  Supplemental: The 3560 switch is uplinked to a Core 3750 Switch, which is where the ip helper address is configured on the server VLAN's interface...So the chain is: Host - 2960 - 3560 - 3750 - DHCP server
Top Expert 2009

Commented:
Is the 2960 a new addition to the network?  Can you post a "show int trunk" from the 2960.

Author

Commented:
The 2960 may be a new addition, not sure.  I believe that all company 2960 switches were recently reconfigured for dot1x authentication.

#show int trunk
Port        Mode             Encapsulation  Status        Native vlan
Gi0/1       desirable        802.1q         trunking      1001

Port        Vlans allowed on trunk
Gi0/1       1-4094

Port        Vlans allowed and active in management domain
Gi0/1       1-4,100,110,150-151,200-202,205,210,215,220,225,230,233,240,255,260-264,270,300,600,650,660,1001

Port        Vlans in spanning tree forwarding state and not pruned
Gi0/1       1-4,100,110,150-151,200-202,205,210,215,220,225,230,233,240,255,260-264,270,300,600,650,660,1001
Top Expert 2009

Commented:
What VLAN is the PC a member of on the 2960?

Author

Commented:
VLAN 205 is the corp VLAN that most users are on, my laptop is on admin VLAN 240
Top Expert 2009

Commented:
Which VLAN are you testing with?  If you put a static IP from that subnet on your test PC, can you communicate with things?

Author

Commented:
I'm testing with only my laptop at this point, which is on the ADMIN VLAN 240.  After assigning static IP info, I wasn't able to ping anything, not even the 2960 switch I was directly connected to.  One bit of behavior that I noticed when I first patched into the switch (before I set my IP to static) is that I was leased valid IP info (from my reservation) from the DHCP server for only about a second until it changed to 169.254.190.178 and knocked me off the network.
Top Expert 2009
Commented:
This one is on us!
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Author

Commented:
You're right.  I just located a doc from the network engineer with instructions for helpdesk to change the default gateway on all the 2960's.  They must have missed this one, I made the change and voila, works now.  Thanks a lot for your help!
Top Expert 2009

Commented:
No prob...glad to help!

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