KaedeShuu
1 Copper

PowerConnect 2848 - DHCP collisions over 2x VLANs

I am having issues with DHCP resolution on a PC2848 with 2 VLANs setup.

My needs are pretty simple.  Setup 2 VLANs with 1 port acting as a "trunk"

I have setup the VLANs as follows:

VLAN Membership
VLAN2 (MainLAN): Ports 1 - 38 (Untagged), 47 - 48 (Untagged)
VLAN3 (GuestLAN):  Ports 39-46 (Untagged), 47 (Tagged)

VLAN Port Configuration
Ports 1 - 38, 47 - 48 have PVID 2
Ports 39 - 46 have PVID 3

I have not done anything with LAG or any other settings.
(side note:  I'd like to set an IP to VLAN2 for management, but CLI tells me only possible on VLAN1... any thoughts?)

What I am finding is that when I put an uplink into port 48 for VLAN2 and an uplink for VLAN3 in port 46, I can no longer get DHCP services over either VLAN. 
DHCP Services are done by seperate Routers.  If I disconnect VLAN3, then VLAN2 can pull the necessary DHCP info.  If I disconnect VLAN2, then VLAN3 can get it's DHCP info. 

I'm just not sure what is going on...

In regards to port 47, I intend to attach that to an access point which will host two SSID's (one for VLAN2 and one for VLAN3).

 

Can anyone see what is going on or make a suggestion on how to do it "right"?

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3 Replies
Moderator
Moderator

Re: PowerConnect 2848 - DHCP collisions over 2x VLANs

It may help to see the configuration of the switch. We can get a better look at how everything is setup.

Something like a show interfaces configuration. And then post that information here.

Does port 46 and 48 go to the same switch, or to different switches? What type of switches are they?

When both are plugged in, can your clients still ping to the DHCP server?

Do the DHCP servers show any errors being logged?

I am not sure you can change the management VLAN on this switch, I will look into it some more and post some more information once I find it.

Thanks

Daniel Covey
Dell EMC| Enterprise Support Services
Get support on Twitter:@DellCaresPRO
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KaedeShuu
1 Copper

Re: PowerConnect 2848 - DHCP collisions over 2x VLANs

Hi Daniel, thanks for looking into things.

To keep the management ip available, I swapped VLAN 2 back to VLAN 1, so conifg is now as follows:

VLAN Membership
VLAN1 (Default): Ports 1 - 38 (Untagged), 47 - 48 (Untagged)
VLAN3 (GuestLAN):  Ports 39-46 (Untagged), 47 (Tagged)

VLAN Port Configuration
Ports 1 - 38, 47 - 48 have PVID 1
Ports 39 - 46 have PVID 3

The DHCP server does not show any errors or requests for DHCP, so it seems things are just getting blocked right at the switch once both uplinks are attached.

Port 46 goes to another switch (also a managed 2848 with default VLAN 1 only) - UnTagged Port
Port 48 goes to another switch (also a managed 2848 with default VLAN 1 only) - UnTagged Port

As far as I know, as they are connected to untagged ports on the other switches, all VLAN information should be stripped.  They should be essentially acting as UnManaged switches.  Side note though that I will want to VLAN enable these in the future.

I tried to get a print out of the configuration, but the CLI on the 2848 is very limited and I can't seem to get a good output... however, here is the output from the command  "show tech-support"


Here's a clip of that that should be relative:

------------------ show vlan ------------------

Vlan       Name                   Ports                Type     Authorization
---- ----------------- --------------------------- ------------ -------------
 1           1            g(1-38,47-48),ch(1-8)       other       Required    
 3     Guest Lan         g(39-47),ch(1-8)        permanent     Required

 

Ports G1 - G38 are as follows:

------------------ show interfaces switchport ------------------
Port : g1  [g2 : g38]
Port Mode: General
Gvrp Status: disabled
Ingress Filtering: true
Acceptable Frame Type: admitAll
Ingress UnTagged VLAN ( NATIVE 😞 1
 
Port is member in:
 
Vlan               Name               Egress rule Port Membership Type
---- -------------------------------- ----------- --------------------
 1                  1                  Untagged          System           


 
Forbidden VLANS:
Vlan               Name              
---- --------------------------------

 

Ports G38 - G 46 are as follows:

Classification rules:
Port : g38  [g39 : g46]
Port Mode: General
Gvrp Status: disabled
Ingress Filtering: true
Acceptable Frame Type: admitAll
Ingress UnTagged VLAN ( NATIVE 😞 3
 
Port is member in:
 
Vlan               Name               Egress rule Port Membership Type
---- -------------------------------- ----------- -------------------- 
 3            Guest Lan             Untagged          Static       

 
Forbidden VLANS:
Vlan               Name              
---- --------------------------------

 

Port G47 is as follows:

Classification rules:
Port : g47
Port Mode: General
Gvrp Status: disabled
Ingress Filtering: true
Acceptable Frame Type: admitAll
Ingress UnTagged VLAN ( NATIVE 😞 1
 
Port is member in:
 
Vlan               Name               Egress rule Port Membership Type
---- -------------------------------- ----------- --------------------
 1                  1                  Untagged          System        
 3          Guest Lan           Tagged           Static       

 
Forbidden VLANS:
Vlan               Name              
---- --------------------------------

 

Port G48 is as follows:

Classification rules:
Port : g48
Port Mode: General
Gvrp Status: disabled
Ingress Filtering: true
Acceptable Frame Type: admitAll
Ingress UnTagged VLAN ( NATIVE 😞 1
 
Port is member in:
 
Vlan               Name               Egress rule Port Membership Type
---- -------------------------------- ----------- --------------------
 1                  1                  Untagged          System       

 
Forbidden VLANS:
Vlan               Name              
---- --------------------------------

 

Classification Rules for Channels 1-8 

Classification rules:
Port : ch1  [ch2, ch3, ch4, ch5, ch6, ch7, ch8]
Port Mode: General
Gvrp Status: disabled
Ingress Filtering: true
Acceptable Frame Type: admitAll
Ingress UnTagged VLAN ( NATIVE 😞 1
 
Port is member in:
 
Vlan               Name               Egress rule Port Membership Type
---- -------------------------------- ----------- --------------------
 1                  1                  Untagged          System        
 3            Guest Lan             Untagged          Static     

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Moderator
Moderator

Re: PowerConnect 2848 - DHCP collisions over 2x VLANs

Are the two other 2848 switches connected to each other? If they we should disconnect them from each other.

Do each of the other 2848 switches have VLAN 2 and 3 added to them as needed? For instance port 46 is for VLAN 3 and connects to another 2848 switch, we need to make sure, that 2848 has VLAN 3 added to it, so it is aware of the VLAN and allows the traffic to pass.

Daniel Covey
Dell EMC| Enterprise Support Services
Get support on Twitter:@DellCaresPRO
Download our QRL app:iOS, Android, Windows
Dell Networking Resources

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