Cisco DHCP Snooping Relay Setup Information

Switch#show ip dhcp snooping
 

Switch DHCP snooping is disabled
DHCP snooping is configured on following VLANs:
1
Insertion of option 82 is enabled
   circuit-id format: vlan-mod-port
    remote-id format: MAC
Option 82 on untrusted port is not allowed
Verification of hwaddr field is enabled
Interface                    Trusted     Rate limit (pps)
------------------------     -------     ----------------
FastEthernet0/1              yes         unlimited
GigabitEthernet0/1           yes         unlimited

 

To enable global "Switch DHCP Snooping":

Switch(config)#ip dhcp snooping

To enable DHCP snoop debugging

Note this only works IF the global dhcp snooping is enabled

debug ip dhcp snooping packet

To disable the DHCP debugging:

no debug ip dhcp snooping packet

Enable Port As Trusted:

You cannot broadcast DHCP unless the port is trusted so here's how you enable trust on a port (it does not work on a vlan I suppose for security reasons):

Switch(config-if)#int fa0/1
Switch(config-if)#ip dhcp snooping trust

Enable Snooping on VLAN:

Switch(config)#
Switch(config)#ip dhcp snooping vlan 1

Allow Untrusted Port:

int fa0/3

ip dhcp snooping information option allow-untrusted

Disable Option 82

If the relay or destination DHCP server doesn't support Option 82 Information it will break your DHCP and you will NOT get an IP/lease.

So disable Option 82 unless you are sure your network supports it:

Switch(config)#no ip dhcp snooping information option

Resources:

https://community.cisco.com/t5/switching/dhcp-snooping-not-working-dropping-packets/td-p/2076543

https://www.askitmen.com/network/ccna/configure-dhcp-snooping/


Tags:

cisco, dhcp, snooping, relay, informationswitch, ip, disabled, configured, vlans, insertion, enabled, circuit, format, vlan, mod, untrusted, verification, hwaddr, interface, pps, fastethernet, unlimited, gigabitethernet, enable, global, quot, config, snoop, debugging, debug, packet,

Latest Articles

  • qemu: could not load PC BIOS 'bios-256k.bin' solution
  • Proxmox How To Custom Partition During Install
  • Hyper-V Linux VM Boots to Black Screen, Storage, NIC Not Found Issues
  • Ubuntu Mint How to Fix Missing/Broken /dev and /dev/pts which causes terminal to immediately close exit and not work
  • How high can a Xeon CPU get?
  • bash fix PATH environment variable "command not found" solution
  • Ubuntu Linux Mint Debian Redhat Youtube Cannot Play HD or 4K videos, dropped frames or high CPU usage with Nvidia or AMD Driver
  • hostapd example configuration for high speed AC on 5GHz using WPA2
  • hostapd how to enable and use WPS to connect wireless devices like printers
  • Dell Server Workstation iDRAC Dead after Firmware Update Solution R720, R320, R730
  • Cloned VM/Server/Computer in Linux won't boot and goes to initramfs busybox Solution
  • How To Add Windows 7 8 10 11 to GRUB Boot List Dual Booting
  • How to configure OpenDKIM on Linux with Postfix and setup bind zonefile
  • Debian Ubuntu 10/11/12 Linux how to get tftpd-hpa server setup tutorial
  • efibootmgr: option requires an argument -- 'd' efibootmgr version 15 grub-install.real: error: efibootmgr failed to register the boot entry: Operation not permitted.
  • Apache Error Won't start SSL Cert Issue Solution Unable to configure verify locations for client authentication SSL Library Error: 151441510 error:0906D066:PEM routines:PEM_read_bio:bad end line SSL Library Error: 185090057 error:0B084009:x509 certif
  • Linux Debian Mint Ubuntu Bridge br0 gets random IP
  • redis requirements
  • How to kill a docker swarm
  • docker swarm silly issues