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Connecting a 2960g to a 4006

mgober
Level 1
Level 1

First time poster here and I am stumped!  I have two Catalyst 4006 switches that are on different floors of the same building.  I want to replace one of the switches with a smaller switch, a WS-C2960g-8tcl.  They are connected via fiber.  I was able to connect the new 2960 switch to the Catalyst 4006.  VTP is on for the 4006.  On the 2960 I verified VTP is being received and the VLANs are listed properly.  On the 2960 I assigned ports 1-7 to VLAN 24 port 8 is the SFP.  On ports 1-7 I am not receiving IP addresses.  I turned trunking on and off, no change either way.  Does anyone have any ideas?  I can post configurations if needed.

Thanks,

Michael

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Jon Marshall
Hall of Fame
Hall of Fame

mgober@crescnt.com

First time poster here and I am stumped!  I have two Catalyst 4006 switches that are on different floors of the same building.  I want to replace one of the switches with a smaller switch, a WS-C2960g-8tcl.  They are connected via fiber.  I was able to connect the new 2960 switch to the Catalyst 4006.  VTP is on for the 4006.  On the 2960 I verified VTP is being received and the VLANs are listed properly.  On the 2960 I assigned ports 1-7 to VLAN 24 port 8 is the SFP.  On ports 1-7 I am not receiving IP addresses.  I turned trunking on and off, no change either way.  Does anyone have any ideas?  I can post configurations if needed.

Thanks,

Michael

Michael

Is the DHCP server in vlan 24 ? If so can you make sure vlan 24 is allowed on the trunk link. If the DHCP server is on a different vlan then where is the vlan 24 L3 interface and does it have an "ip helper-address" command configured.

Can you answer the above and post out of "sh int trunk" from the 2960G.

Jon

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5 Replies 5

Jon Marshall
Hall of Fame
Hall of Fame

mgober@crescnt.com

First time poster here and I am stumped!  I have two Catalyst 4006 switches that are on different floors of the same building.  I want to replace one of the switches with a smaller switch, a WS-C2960g-8tcl.  They are connected via fiber.  I was able to connect the new 2960 switch to the Catalyst 4006.  VTP is on for the 4006.  On the 2960 I verified VTP is being received and the VLANs are listed properly.  On the 2960 I assigned ports 1-7 to VLAN 24 port 8 is the SFP.  On ports 1-7 I am not receiving IP addresses.  I turned trunking on and off, no change either way.  Does anyone have any ideas?  I can post configurations if needed.

Thanks,

Michael

Michael

Is the DHCP server in vlan 24 ? If so can you make sure vlan 24 is allowed on the trunk link. If the DHCP server is on a different vlan then where is the vlan 24 L3 interface and does it have an "ip helper-address" command configured.

Can you answer the above and post out of "sh int trunk" from the 2960G.

Jon

mgober
Level 1
Level 1

DHCP is not on the same subnet.  The old 4006 that I am replacing was on Vlan 24 and it was working then.  I also tried manually assigning an IP that is in the VLAN 24 range but to no avail. 

Here are the results from the 2960:

sw7.1#sh int trunk

Port        Mode             Encapsulation  Status        Native vlan
Gi0/8       on               802.1q         trunking      1

Port        Vlans allowed on trunk
Gi0/8       1-4094

Port        Vlans allowed and active in management domain
Gi0/8       1-10,24,32-33,50-54,99-101

Port        Vlans in spanning tree forwarding state and not pruned
Gi0/8       1-10,24,32-33,50-54,99-101

Can you post config of 2960 + "sh ip int brief" off 2960G.

Also post config from 4006. I'm assuming the 4006 is routing for the vlans ??

Jon

  On the 2960 ports make sure you have portfast turned on for ports 1-7 .  If you can't statically assign one and get around then the  trunk is most likely not working correctly . If you can post the uplink configs for the 2960 and the config on the 4006 .

mgober
Level 1
Level 1

Eureka, I figured it out!  The router module on the 4006 that is being replaced was handling the routing for VLAN 24.  When I looked at the gig interface that I was plugged into I noticed that VLAN 24 was not defined as a sub interface.  I assigned the ports on the 2960 to VLAN 50, which was defined as a sub interface, DHCP and IP traffic began to function.  Now I know that my trunk is working properly.  When I go to decommission the 4006 I will add a Vlan 24 sub interface to the remaining 4006.

Thanks, Jon and Glen for your help I truly appreciate it!

Michael

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