VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210

VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-15 07:44:08
Hardware Version: V1
Firmware Version: 1.0.1 Build 20171225 Rel.67244(s)

I would like to ask help. I have a Cisco SG300 switch running as Layer 3, with VLAN 20, 21. Enabled dhcp relay for VLAN 20 and 21. Then on the TP Link SG3210, I set VLAN 20 and 21 then both connected to the trunk line on port 1. Now the problem is when the client connect to SG3210 on port 2, which is under VLAN 20, it can get IP address of the VLAN 20 subnet. However, when the client connect to SG3210 on port 3, which is under VLAN 21, it can still get an IP address but of the VLAN 20 subnet.

 

Any help here would greatly appreciated. Any links to a detailed manual for this equipment.

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9 Reply
Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-19 08:10:20

rkmalbacias wrote

I would like to ask help. I have a Cisco SG300 switch running as Layer 3, with VLAN 20, 21. Enabled dhcp relay for VLAN 20 and 21. Then on the TP Link SG3210, I set VLAN 20 and 21 then both connected to the trunk line on port 1. Now the problem is when the client connect to SG3210 on port 2, which is under VLAN 20, it can get IP address of the VLAN 20 subnet. However, when the client connect to SG3210 on port 3, which is under VLAN 21, it can still get an IP address but of the VLAN 20 subnet.

 

Any help here would greatly appreciated. Any links to a detailed manual for this equipment.

 

If you have two DHCP server for VLAN 20 and VLAN 21, you don't need to use DHCP relay.

If you have only one DHCP server, you can refer to the FAQ. https://www.tp-link.com/en/support/faq/1630/

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Re:Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-20 00:55:16

I have read that tutorial and tried to follow it. It works though, but for VLAN 20 only. I only have 1 DHCP server. My setup work with all my cisco SG300 switches.

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Re:Re:Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-20 06:30:01

rkmalbacias wrote

I have read that tutorial and tried to follow it. It works though, but for VLAN 20 only. I only have 1 DHCP server. My setup work with all my cisco SG300 switches.

 

Could you post your configuuration screenshots of DHCP relay? Then we can check if it's related to the configuration.

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Re:Re:Re:Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-20 06:35:30

Sure, but it is quite long. I'll just have to past the link where I posted in Spicework about this issue. I've had screenshot as well:

 

https://community.spiceworks.com/topic/2226999-how-to-setup-vlan-with-relay-on-tp-link-with-cisco-sg300

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Re:Re:Re:Re:Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-20 07:09:45

Did you Cisco switch port connected to TP-Link switch also set PVID as 20? Maybe you can try to use PVID 1.

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Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-20 07:23:08

Yes and yes. The VLAN 21 can get IP from the said DHCP server. However, the subnet it gets is the subnet of the VLAN 20.

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Re:Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-21 02:04:31

rkmalbacias wrote

Yes and yes. The VLAN 21 can get IP from the said DHCP server. However, the subnet it gets is the subnet of the VLAN 20.

 

Just find one thing, if you have set DHCP relay on SG300 and it works normally, then when you connect SG3210 to SG3210, you don't need to set DHCP relay on SG3210 again. Just keep the VLAN correct, when SG300 receive the data from SG3210 and different VLAN, SG300 will transfer the DHCP request to DHCP server.

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Re:Re:Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-22 04:40:31 - last edited 2019-08-22 04:41:36

I'm not sure if I understood your point, sir. My setup is like this, Cisco SG300 then to connect TPLink SG3210. I used Port 10 of Cisco SG300 now as trunk (uplink) then Set Port 8 of TPlink SG3210 as Trunk as well. The problem is when client connect to Port 4-6 of TPlink that is under VLAN21, it can get IP Address from the DHCP server but the subnet is the subnet of VLAN 20. I tried adding another VLAN, 30, to be exact, its ip address should be 192.168.30.X, however, it get the ip address of 192.168.20.X, which is the ip network of VLAN 20.

 

I'm not really sure if I did really understand how VLAN Trunking works in SG3210. With my Cisco SG300, it is just so straight forward. just wondering.

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Re:Re:Re:Re:VLAN Trunk and DHCP Relay on CISCO SG300 to TP Link SG3210
2019-08-23 06:50:43

rkmalbacias wrote

I'm not sure if I understood your point, sir. My setup is like this, Cisco SG300 then to connect TPLink SG3210. I used Port 10 of Cisco SG300 now as trunk (uplink) then Set Port 8 of TPlink SG3210 as Trunk as well. The problem is when client connect to Port 4-6 of TPlink that is under VLAN21, it can get IP Address from the DHCP server but the subnet is the subnet of VLAN 20. I tried adding another VLAN, 30, to be exact, its ip address should be 192.168.30.X, however, it get the ip address of 192.168.20.X, which is the ip network of VLAN 20.

 

I'm not really sure if I did really understand how VLAN Trunking works in SG3210. With my Cisco SG300, it is just so straight forward. just wondering.

 

Suppose that your topology is as follows.

DHCP server----SG300----SG3210----DHCP client

 

When SG3210 receive the DHCP packets from DHCP clients, it will forward the packets to DHCP server thorugh its layer3 interface. SG3210 only has one layer3 interface and you have set it for VLAN 20, so the DHCP packets will be forward to DHCP server through VLAN and use the source IP of 192.168.20.x, then DHCP clients will get the IP of VLAN 20.

 

So I think SG3210 may not meet your demand. If your SG300 supports DHCP relay and layer3 interface, you can configure DHCP relay on SG300 rather than SG3210.   

DHCP server----(VLAN30)SG300(VLAN10&20)----(VLAN10&20)SG3210(VLAN10)----DHCP client

                                                                                                                   (VLAN20)----DHCP client

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