topic Re: how to use dhcp relay agent in extreme summit x460-24t in ExtremeSwitching (EXOS/Switch Engine)

how to use dhcp relay agent in extreme summit x460-24t

sumeetinanicdot — Sat, 24 Jul 2021 06:38:14 GMT

Here are my settings for vlan 113

configure vlan vlan113 tag 113
configure vlan vlan113 add ports 21-24 tagged
configure vlan vlan113 ipaddress 172.16.113.1 255.255.255.0
enable ipforwarding vlan vlan113
configure vlan vlan113 dhcp-address-range 172.16.113.2 - 172.16.113.200
configure vlan vlan113 dhcp-options default-gateway 172.16.113.1
configure vlan vlan113 dhcp-options dns-server 196.1.105.47
enable dhcp ports 21-24 vlan vlan113

as you can see that this allows my L2 devices dealing with tagged packets of vlan 113 to get automatic IP.

My understanding is that DHCP relay agent allows getting IP from DHCP server of another network.

How can I configure my vlan 114 so that devices in vlan 114 get IP from DHCP server of vlan 113 ?

Actually , once I verify DHCP relay feature in this switch then I will test DHCP relay feature of another device.

I guess verifying DHCP option 82 is same as DHCP relay agent.

Thanks.

Re: how to use dhcp relay agent in extreme summit x460-24t

Stefan_K_ — Sat, 24 Jul 2021 19:03:19 GMT

Hi,

I don’t really understand what you are trying to achieve.

You have DHCP-Server configured directly on your switch for VLAN113. And now you want to relay VLAN114 to this DHCP-Server? This won’t be possible I guess and also Clients on VLAN114 would receive the same IP-Addresses as on VLAN113!? Why don’t you configure DHCP-Server for VLAN114 directly on the switch like for VLAN113?

DHCP Relay is used to forward DHCP packets to an “external” (e.g. Windows Server) DHCP-Server, that is on another VLAN than the clients.

This would be done like this:

configure bootprelay add <IP-Address> vr VR-Default
enable bootprelay vlan VLAN113
enable bootprelay vlan VLAN114
enable bootprelay vlan Server-VLAN

Re: how to use dhcp relay agent in extreme summit x460-24t

sumeetinanicdot — Sat, 24 Jul 2021 22:26:35 GMT

I am guessing server-vlan in your example is different from 113 and 114.

what is <ip-address> ?

My purpose is to verify DHCP relay functionality .

I want to execute setup shown in https://www.geeksforgeeks.org/dhcp-relay-agent-in-computer-network/ .

Suppose vlan 114 config is

configure vlan vlan114 tag 114
configure vlan vlan114 add ports 21-24 tagged

i thought that vlan 114 clients will get ip from dhcp pool of vlan 113 if i add dhcp relay in vlan 114 to point to dhcp server in vlan 113 . is that wrong ?

Re: how to use dhcp relay agent in extreme summit x460-24t

Stefan_K_ — Sat, 24 Jul 2021 22:59:12 GMT

I am guessing server-vlan in your example is different from 113 and 114.

Yes, this is the VLAN where the DHCP-Server is located.

The IP-Address of the server, in your example 192.168.2.2.

In this case you don’t need this configuration:

configure vlan vlan113 dhcp-address-range 172.16.113.2 - 172.16.113.200
configure vlan vlan113 dhcp-options default-gateway 172.16.113.1
configure vlan vlan113 dhcp-options dns-server 196.1.105.47
enable dhcp ports 21-24 vlan vlan113

This configures a DHCP-Server on the switch itself, but in your Link the DHCP-Server is another device.

This is basically right. If the DHCP-Server is on VLAN113 you need to remove this configuration:

configure vlan vlan113 dhcp-address-range 172.16.113.2 - 172.16.113.200
configure vlan vlan113 dhcp-options default-gateway 172.16.113.1
configure vlan vlan113 dhcp-options dns-server 196.1.105.47
enable dhcp ports 21-24 vlan vlan113

and add this configuration

configure bootprelay add <IP-Address of DHCP-Server> vr VR-Default
enable bootprelay vlan VLAN113
enable bootprelay vlan VLAN114

Do you have a separate DHCP-Server already?

Re: how to use dhcp relay agent in extreme summit x460-24t

sumeetinanicdot — Sun, 25 Jul 2021 08:48:06 GMT

actually , i don’t have a separate dhcp server .

i was hoping to use dhcp server of extreme switch itself .

is it possible to use one vlan (114) as dhcp relay and another vlan (113) as dhcp server ?

Re: how to use dhcp relay agent in extreme summit x460-24t

Stefan_K_ — Sun, 25 Jul 2021 16:33:26 GMT

Pretty sure that it won’t work. Not sure if you can even configure the DHCP relay to an IP-Address that the switch holds, but the main problem would be that you can’t configure multiple scopes on the switch on the same VLAN.

If you only want to test the functionality you can use your client or a Raspberry Pi or anything else as an DHCP-Server, just need to install some software.

If you want to have a productive DHCP-Server for both VLANs you have to configure DHCP-Server on the switch for both VLANs, but not via DHCP-Relay.

Best regards
Stefan

Re: how to use dhcp relay agent in extreme summit x460-24t

sumeetinanicdot — Mon, 26 Jul 2021 11:55:34 GMT

ok, got it .

So , i will try to use extreme switch as dhcp relay agent .

I have to implement https://www.geeksforgeeks.org/dhcp-relay-agent-in-computer-network/ .

I think - I will need atleast 2 vlans . say , vlan 113 has DHCP relay and 114 has DHCP server . Will that be alright ?

How do I configure 113 and 114 on extreme switch . I am not sure about that .

I have windows/linux desktop available which can act as DHCP server . Do you know any reliable free DHCP server software for either OS ?

Thanks.

Re: how to use dhcp relay agent in extreme summit x460-24t

Stefan_K_ — Mon, 26 Jul 2021 18:55:51 GMT

The switch needs an IP-Address on both VLANs.

IP-forwarding needs to be enabled on both VLANs.

DHCP-Relay (bootprelay) needs to be enabled on the VLAN where the server is located and on the VLAN where the clients are located, so in your case on both VLANs.

You can find the config for bootprelay above.

On the DHCP-Server you need to create two scopes.

https://linuxconfig.org/what-is-dhcp-and-how-to-configure-dhcp-server-in-linux

Re: how to use dhcp relay agent in extreme summit x460-24t

sumeetinanicdot — Mon, 26 Jul 2021 19:55:18 GMT

ok .

I will try that and get back with details .

thanks .