Port not working for access to vlan

[ACarter51016]

The senior IT person for our company recently passed away from, wait for it, COVID-19. I have been tasked with taking over.

I am the network and hardware guy but I didn't handle any of the Cicso we have. I don't have a lot of experience with it but I am learning now. I have researched this for about 2 weeks now and haven't had any success. We are adding an industry-specific piece of equipment that must be on the correct vlan. 

The switch is a 3750x.

The issue I am having is using a single open port on the switch. We have 3 vlans:

10.2.0.0
10.2.2.0
10.2.3.0

When I plug into this port, I get an address from the DHCP server on 10.2.2.0

I want the port to be on the 10.2.0.0 vlan and I thought I was successful in adding it. But even after that, I get an address from the 10.2.2.0 network and can't access anything on the 10.2.0.0 vlan.

However, the devices on the 10.2.0.0 vlan are able to communicate with the 10.2.2.0. Just this port can't do it. 

My goal is to make this port on the 10.2.0.0 vlan and successfully communicate with both the 10.2.0.0 and 10.2.2.0 networks.

How can I check this and find what is causing this from happening? I really appreciate it.

[Richard Burts]

Thanks for posting the configuration. It answers some questions and raises some new questions.

- it does show that the switch is doing DHCP for vlans 1 and 10. The switch is not doing DHCP for vlans 2 or 9 or 250. So where is the DHCP for those vlans being done?

- there is not any helper-address configured on those vlans. So the switch is not forwarding DHCP requests for those vlans. This suggests that there is a DHCP server locally connected in each of those vlans. Is this correct?

- in addition to 1/0/20 you have 2 other ports where devices are connected and in vlan 9 (1/0/13 and 1/0/37). Are these devices working ok? Or do they have the same symptoms of being in vlan 9 but getting IP addresses in vlan 2?

- perhaps the output of show cdp neighbor on the switch might help us understand what other devices might be in the network.

[ACarter51016]

#show cdp neighbor
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID
SEP706E6D11E5BA Gig 1/0/25 173 H P M IP Phone Port 1
SEPF8A5C59C66D0 Gig 1/0/8 178 H P M IP Phone Port 1
SEPEC1D8BBAE4EA Gig 1/0/17 172 H P M IP Phone Port 1
SEP007686CE4EAC Gig 1/0/3 144 H P M IP Phone Port 1
SEPEC1D8BBBF602 Gig 1/0/38 125 H P M IP Phone Port 1
SEPF8A5C59EABB8 Gig 1/0/11 165 H P M IP Phone Port 1
SEPEC1D8BBB5C60 Gig 1/0/20 129 H P M IP Phone Port 1
SEP0024142F04A5 Gig 1/0/45 165 H P M IP Phone Port 1
SEPC444A03F5B52 Gig 1/0/40 165 H P M IP Phone Port 1
SEP706E6D1038DE Gig 1/0/36 154 H P M IP Phone Port 1
SEPEC1D8BBAFD00 Gig 1/0/43 158 H P M IP Phone Port 1
Switch2 Gig 1/1/1 179 R S I WS-C3750X Gig 1/1/1
Switch2 Gig 1/1/2 179 R S I WS-C3750X Gig 1/1/2
sw1 Gig 1/0/47 164 R S I WS-C3750X Gig 1/0/12

As far as DHCP I cannot locate any server other than the switch IP

This is a secondary  domain controller.  we would like to put it on with a static IP for vlan 9.

On the cdp it states this port is on Po1 and is an IP Phone.

ipconfig /all | find /i "DHCP Server" returns switch ip.

[Richard Burts]

Thanks for the output. I am surprised to see that 1/0/20 appears to have a phone connected - and potentially some IP host connected through the phone.

Have you checked on the other devices that are connected in vlan 9? Are they working? Or do they have the same issue about getting DHCP from vlan 2?

Would you post the output of show interface trunk from this switch?

What can you tell us about the other switches that connect to this switch (Switch2 and sw1)? Can you post the config of these switches?

[ACarter51016]

#show interface trunk

Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 250

Port Vlans allowed on trunk
Po1 1-4094

Port Vlans allowed and active in management domain
Po1 1-2,10,20,90,100,250

Port Vlans in spanning tree forwarding state and not pruned
Po1 1-2,10,20,90,100,250

[ACarter51016]

Both switches are Cisco 3750 x

sw1 is the master

[ACarter51016]

All other devices in vlan 9 are getting correct ip's.

[ACarter51016]

sw1#show interface trunk

Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 250

Port Vlans allowed on trunk
Po1 1-4094

Port Vlans allowed and active in management domain
Po1 1-2,9,100,250

Port Vlans in spanning tree forwarding state and not pruned
Po1 1-2,9,100,250

[dadamsjrsnoopy]

Not sure what you are asking.

To make sure a port has access to a vlan, that switchport must be a membere of that vlan.

By doing show vlan brief, you can see which ports are in which vlans.  Before you make any changes on a switch that has the default configuration, all witchports will be in van1 and if you do a dir flash:, there will be no vlan.dat file.

The way to make a switchport or switchports a member of a vlan:

config t

int range gi1/0/1-12

switchport access vlan xxx (xxx of course being the vlan number)

you should get a response vlan xxx created.

type end and then wr to save the configuration change.

You should now have a vlan.dat file and if you do show vlan brief, you should see your changes.

David Adams

[ACarter51016]

Thank you, I did as you requested and it shows that the port is in the vlan 9.
However we are still receiving an IP from DHCP that is not on vlan 9 scope.

[dadamsjrsnoopy]

I would do show ip int brief.  This will show all interfaces, their status and if they have an IP address, what the IP address is.

If it is receiving an IP address by DHCP that is not in the scope for vlan 9, I would go to the DHCP source and look to see why.

Since I am not there and have no actual access to look at things for you, I am not sure I can be of much more help.

David Adams

Mobile, AL