DHCP didn't cross TRUNK

[h.dam]

Hi guys,

I' ve an DHCP issue that works if the link is access mode but didn't work if I change it to trunk mode. Here's the config:

SW-server: (with vlan database created)

ip routing

ip dhcp pool VLAN-MGT

network 10.0.0.0 255.255.255.0

default-router 10.0.0.254

!

interface vlan 500

ip address 10.0.0.254 255.255.255.0

!

interface G1/0

switchport mode trunk

switchport trunk allowed vlan 500

!

SW-client: (with vlan database created)

ip routing

interface vlan 500

ip address dhcp

!

interface G1/0

switchport mode trunk

switchport trunk allowed vlan 500

!

In summary:

1. if interface G1/0 is access mode , interface vlan500 on SW-client gets IP address

2. if interface G1/0 is trunk mode, no IP address on SW-client interface vlan500.

Your explanations are very appreciated.

[h.dam]

Hello,

Finally, I found this command applied on trunk interface:

mac-address-table secure maximum 24 GigabitEthernet0/1/2

By removing it, it works immediately.

I didn't understand why this line block the traffic. Its not an ACL.

Thanks for all of you guys.

[PaulP · Accepted solution]

User error :)

I hope we pointed you in the right direction for you to find this configuration.

Don't forget to mark helpful if we did.

Paul

[Georg Pauwen]

Hello,

glad that you found the problem/solution. No way to guess this...:)

[Moses Fernandes]

I'm glad to know that you found the solution for your issue.

I'm kind of stumped with the solution. (If port security was an issue, Could you also let us know the violation type selected, what mode did the port go into when there was a violation eg: err-disa../Shutdown? )

If possible can someone please shed some light to this solution.

How can --> mac-address-table secure maximum 24 GigabitEthernetxx act differently on a Access port and a Trunk port.

I assume that the above command should also block (DHCP Request) while the port is in access mode.

(No offence to anyone. I'm just curious to know how the above command works differently on an access port vs Trunk port.)

Regards,

Moses.

[h.dam]

Hello,

In my case, this command doesn't work on trunk interface. That is why I remove it.

I didn't try on access mode. But I think it should work.