VLAN DHCP problem between Router and Switch

5 pts.
Tags:
Cisco Catalyst 520
DHCP
Netgear switches
VLAN
VLAN configuration
I have a Cisco SA520 Router connected to a Netgear FS726TP Switch. Router has 3 Vlans. 
Management VLAN 1 /29 
Hosts VLan 5 /27 
VoIP Vlan 10 /27 
Router Ports 1 and 2 are setup up identically, in Trunk Mode each port and all VLAN's should be accessible through it. 
Port 3 Vlan 5 
Port 4 Vlan 10 
Swithc is set like this 
Vlan 1: Port 24 untagged, port 26 Tagged (Router) 
Vlan 5: All ports Tagged 
Vlan 10: Ports 1 to 12 Tagged and port 26 tagged port 24 tagged 
PVID: Port all Ports VLAN 5 
So I can get an IP from DHCP of vlan 1 conneted to port 24 on my management laptop, but I can't get IP on hte other ports, I tried untagged or tagged and is the same. If I connect to the router on the port 3 or 4 I get an IP for each vlan. I will set the Phones with Mac address on DHCP so they can take an IP from Vlan10 and the PC's connected behind the phone will stay on Vlan 5 ANy ideas why I'm not getting DHCP replay behind the switch?


Software/Hardware used:
cisco sa520, netgear fs726tp
ASKED: September 4, 2011  7:16 PM
UPDATED: March 31, 2012  5:10 PM

Answer Wiki

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Just at first glance, seems there’s a few minor glitches in the config:

Vlan 5: All ports Tagged + PVID: Port all Ports VLAN 5 = Kinda killing yourself there
– PVID = Native VLAN = Untagged ports, so tagging them is counter-productive

You fail to mention how the SA520 is set-up to Handle DHCP: What is doing DHCP? Is the DHCP “server” on a different VLAN than the Hosts? Do you have DHCP forwarding / ip helper addresses configured?

Just from what you’ve written, You COULD config the switch as follows:

- VLAN 5: All ports untagged, set PVID to VLAN 5 (PCs dont do VLAN tagging)
- VLAN 10: Tagged on all ports (Phones can read/write VLAN tags)
- Port 26 (to router) : Untagged VLAN 1, Tagged: VLAN 5 / 10
- Ensure DHCP server is set up, and router has ip helper addresses pointed to the DHCP servers IP address

Not sure why you’d need ports 3/4 set to the VLANs if 1/2 are Trunking w/ ALL VLANs…

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