SG500X-48P vs SG550X-48MP DHCP Relay

[sgear@orizonaero.com]

Hello,  We have a site that is successfully setup using an SG500X-48P as the Layer 3 router and we are able to obtain IP's from DHCP without any issue at this location using this configuration.

We recently setup a new site with SG550X-48MP Switches and there are some slight differences between the new switches and old.  Intervlan routing seems to be working ok as I can get from one VLAN to another without any problems, however, we are having issues with getting DHCP addresses assigned to VLANs other than the same one as our Server is on (VLAN 100).

To work around this problem, we created a trunk port for VMware to use and assigned the NIC to that server and added multiple network cards using the different VLANs we need to get IP addresses.  

This is not ideal and I would like to get this working natively as it does in our other location.

Does anyone know why DHCP Traffic would not be reaching the destination Server?  WE have defined the IP in the switch and verified that DHCP relay is enabled.  Also the DHCP Interfaces table is configured with each VLAN Interface, Interface IP and DHCP Enabled.

I can upload a config file if that would help understand how it is configured now?

[Jaderson Pessoa]

sgear@orizonaero.comhello,

Could you share output from:

show ip dhcp relay

if possible, post here current configuration of your switch.

This configs works for me:

sw(config)# ip dhcp relay enable

sw(config)# address x.x.x.x y.y.y.y

sw(config)# interface vlan x

sw(config-vlan)# ip dhcp relay enable

Thanks in advance.

[sgear@orizonaero.com]

I am attaching the running config as a text file.

Here is the output from show ip dhcp relay

show ip dhcp relay
DHCP relay is Enabled
Option 82 is Enabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 10,20-21,50,60,70,100,150,160,170,210,220
Active: 10,20-21,50,60,70,100,150,160,170,210,220
Inactive:
Servers: 10.40.100.11

[Jaderson Pessoa]

sgear@orizonaero.com right,

You configuration its ok. 

Could you try this;

on vmware, go to host: configuration > networking > interfaces > enable promiscuous mode and test your dhcp relay.

[sgear@orizonaero.com]

Thanks for the reply!  I have tried enabling promiscuous mode on both the port group and virtual switch with no change in the result.  It tries to pull an ip and eventually times out and gets a 169.x.x.x address.

One question I have not found a reliable answer on is if I need to have DHCP relay turned on for the subsequent switches connected to this "router" switch.  I have seen some sites that have mentioned it should be turned off and others say on.

Currently it is turned off on the office switch that connects to the OLA-RTR01 and the office switch is where my clients are located.

[Jaderson Pessoa]

One question I have not found a reliable answer on is if I need to have DHCP relay turned on for the subsequent switches connected to this "router" switch.  I have seen some sites that have mentioned it should be turned off and others say on.

the answser is no.. you just need turn on it on switch L3 that provide VLANS for network.

[sgear@orizonaero.com]

Thank you!

Do I need to have L3 turned on for uplink ports to or from the "router" switch?

Sorry for the simple questions but outside of this location and with the SG500X series it just seemed to work for us.

Thanks Again!

[Jaderson Pessoa]

Let me try explain for you.

You have a L3 device RW_A that has two vlans   10 and 20 with configurations below;

vlan 10: 192.168.1.1 255.255.255.0 << this vlan need dhcp relay under vlan configuration

vlan 20: 192.168.2.1 255.255.255.0 << this vlan need dhcp relay  under vlan configuration

Now you input other switch L3_B that you just replicate those vlan 10 and 20, but here.. there arent IP address under vlans: you dont need set here dhcp relay

If this L3_B above has other vlans like 30 and 40 with IP address under configuration, you will needs a dhcp relay configured under vlans.

Obs: So, you need apply it under VLAN or PHYSICAL interfaces. 

To resume: ip dhcp relay is configured under interfaces that is routed by L3 device.

Regards,

[sgear@orizonaero.com]

Thanks again for responding.

All VLANs are defined on the L3 switch which we call our "router" it is behind the firewall and have several switches as L2 configured behind the L3 switch for our location.

I tried promiscuous mode again with no success.  It seems my Switch is configured correctly for IP-Helper but DHCP still times out when trying to get an address from a client.

Any other ideas you can think of to try?

[sgear@orizonaero.com]

I am including a Crude Layout of our location.  I have done some more testing this morning and it appears that I am unable to reliably get an ip from any switch outside of the Core SG550x we have configured with the VLANs and IP Helper.

I suspect there may be a bad SFP module or stacking cable in the Distribution Switch Stack that consists of 3 SG550x Switches, 2 48 Port and a 24 Port.

When I plug into the Distribution stack I can "sometimes" get an ip.  I have tried plugging into each switch in the stack including the master which has the uplink to the Core Switch.

Please see the drawing and I will also upload the config from the Distribution Switches and let me know if you see anything out of sorts.

[sgear@orizonaero.com]

Please see attached config for Distribution Switches

[Jaderson Pessoa]

sgear@orizonaero.com hello,

Please, clarify it for me;

ON OLA_RTR01

ip dhcp relay address 10.40.100.11

interface vlan 100
name workstations
ip address 10.40.100.1 255.255.255.0
ip dhcp relay enable

ON OLA_RTR01

interface GigabitEthernet1/0/5
description "access-point engineering"
switchport mode trunk
switchport access vlan 60   << this command is sets on many interfaces in switchport mode trunk, it is not necessary, you can remove it.
switchport trunk native vlan 10
switchport trunk allowed vlan remove 1-9,11-49,51-209,211-219,221-4094

no macro auto smartport

in many of your interfaces you are removing many vlans traffic.

Could appoint me how this devices and which port is plugged?

OLA_DSSW01 ><  OLA_RTR01   << what are interfaces connecting them?

OLA_DSSW01 >< DHCP SERVER << what is interface that connect your DHCP server?

Regards,

[sgear@orizonaero.com]

OLA-DSW01 uplinks to OLA-RTR01 on port XG4 of the master switch and connects to port XG3 of unit 2.

The DHCP Server is configured on a vswitch with 4 NICS in VMware and connects to ports Gi2/0/17 and Gi1/0/16 and Gi1/0/3 and Gi2/0/1 in a NIC team.

Thanks,

[sgear@orizonaero.com]

So I must have an issued with the stack of switches OLA-DSW01 because I connected another set of switches back to the OLA-SW01 (router) via an Ethernet Cable, plugged a client in locally to those switches and am able to get an ip from DHCP without hesitation.

I think I am going to get some new SFP's and new OM3 Fiber Cable to replace the current ones to see if that helps solve anything.

[Jaderson Pessoa]

sgear@orizonaero.com I think that your SFP isen't the problem. 

Could you clarify it for me?

The DHCP Server is configured on a vswitch with 4 NICS in VMware and connects to ports Gi2/0/17 and Gi1/0/16 and Gi1/0/3 and Gi2/0/1 in a NIC team.

ON DSW01

interface GigabitEthernet1/0/16
switchport mode trunk
switchport access vlan 60        << could you remove this configuration?
switchport trunk native vlan 60
switchport trunk allowed vlan remove 1-59,61-69,71-4094   << could you remove this configuration?
no macro auto smartport

interface GigabitEthernet1/0/3
switchport mode trunk
switchport access vlan 60       << could you remove this configuration?
switchport trunk native vlan 60
switchport trunk allowed vlan remove 1-59,61-69,71-4094  << could you remove this configuration?
no macro auto smartport

interface GigabitEthernet2/0/17
switchport mode trunk
switchport access vlan 60        << could you remove this configuration?
switchport trunk native vlan 60
switchport trunk allowed vlan remove 1-59,61-69,71-4094  << could you remove this configuration?
no macro auto smartport

interface GigabitEthernet2/0/1
switchport mode trunk
switchport access vlan 60       << could you remove this configuration?
switchport trunk native vlan 60
switchport trunk allowed vlan remove 1-59,61-69,71-4094  << could you remove this configuration?
no macro auto smartport

OLA-DSW01 uplinks to OLA-RTR01 on port XG4 of the master switch and connects to port XG3 of unit 2.

ON RTR01
interface GigabitEthernet1/0/4
switchport access vlan 60

interface GigabitEthernet2/0/3
switchport mode trunk
switchport access vlan 100
switchport trunk allowed vlan remove 1-4,6-99,101-4094

This interfaces has mismatch configuration...  

Please, confirm if that i took correctly interfaces.