05-21-2024 03:58 AM
Hello, I have a problem on a switch c9407r in version 17.9.4a.
I have a device connected on a port (Gi1/0/11) on vlan 601 that sends a dhcp discovery request.
If I capture the uplink interfaces to the gateway (PO10) I can see the dhcp response with the dhcp offer frame.
However, on my equipment's interface, the dhcp offre frame doesn't go through.
Searching the logs I came across this:
113987: May 21 07:48:28.219: DHCP_SNOOPING: direct forward dhcp replyto output port: GigabitEthernet1/0/11.
113988: May 21 07:48:28.219: DHCP_SNOOPING: process new DHCP packet, message type: DHCPOFFER, input interface: Po10, MAC da: 408c.f451.12f4, MAC sa: 7854.bd5a.chfu, IP da: 192.185.1.5, IP sa: 192.185.1.1, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 192.185.1.5, DHCP siaddr: 192.232.43.12, DHCP giaddr: 192.185.1.1, DHCP chaddr: 408c.f451.12f4, efp_id: 21390295604, vlan_id: 601, bootpflag:0x0(Unicast)
113989: May 21 07:48:28.219: DHCP_SNOOPING: calling forward_dhcp_reply
113990: May 21 07:48:28.219: platform lookup dest vlan for input_if: Port-channel10, is NOT tunnel, if_output: NULL, if_output->vlan_id: 99999, pak->vlan_id: 601
113991: May 21 07:48:28.219: DHCP_SNOOPING: vlan 601 after pvlan check
113992: May 21 07:48:28.219: DHCP Memory dump is printed for direct forward reply
I can't find the problem. I tried to see if it could be dhcp snooping or device-tracking without success.
Do you have an idea of the problem?
Solved! Go to Solution.
05-23-2024 10:39 PM
The problem has been found. Thank you for your help.
It was a fault on the link to the equipment.
However, I can't figure out why a link fault was preventing the dhcp offer from getting through.
There were a lot of input errors
05-21-2024 04:33 AM
Can you draw simple topolgy and point where you enable dhcp snooping
MHM
05-21-2024 07:32 AM
Hi MHM thank you for your reply
Here is a diagram of the topology as requested
Have a nice day !
05-21-2024 08:20 AM - edited 05-21-2024 08:20 AM
in L3SW you need
ip dhcp relay information trust-all
or under interface
ip dhcp relay information trust
MHM
05-21-2024 08:09 AM
Hello,
Have you configured the interface that received the OFFER frame as a trusted port? When configuring DHCP Snooping allports are untrusted by default and wont process DHCP server type packets.
-David
05-21-2024 10:41 PM - edited 05-21-2024 10:42 PM
Yesterday I tried to connect my PC to the Gi1/0/11 port in vlan 601 and I received an IP **bleep** directly.
So I think the problem is between my equipment and the switch sw02. Does the fact that the equipment sends ARP requests with an APIPA **bleep** cause the problem ?
05-21-2024 11:37 PM
did you check my previous comment ?
also I see only device where is DHCP server connect or it local in L3SW?
MHM
05-22-2024 12:08 AM
Yes I will try your command on the swL3.
There are two dhcp servers on the network. The l3SW has two ip-helper to the dhcp servers
05-22-2024 12:17 AM
this correct ?
05-22-2024 12:25 AM
Like that :
05-22-2024 12:44 AM
05-22-2024 02:11 AM
Yes, during my test i connect PC on port Gi1/0/11 like the équipement.
Port configuration are :
switchport mode access
switchport access vlan 601
equipment on port gi1/0/11 is on vlan 601, dhcp discovery is on vlan 601
05-23-2024 10:39 PM
The problem has been found. Thank you for your help.
It was a fault on the link to the equipment.
However, I can't figure out why a link fault was preventing the dhcp offer from getting through.
There were a lot of input errors
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