DHCP HELP Please.......

[prerak_patel]

I have all DHCP clients and server on same VLAN in the same subnet on CAT4507.

I can also ping DHCP server, but the clients are not getting IPs. I've checked DHCP config on server seems to be OK. When I turn on debug I get following:

1w3d:

-----Additional Debug------

1w3d: DHCP process ID FFFFFFFF status 0

1w3d: DHCP Network Discovery is disabled

1w3d: DHCP NetDiscovery Informs 0 Discovers 0 Period 0

[Roberto Salazar · Accepted solution]

can you make sure that "spanning-tree portfast" is enabled on the client port and server port? Can you also post the client and server port config, if possible?

[prerak_patel]

I don't have spanning-tree port-fast enabled. I plugged in all cables into a small switch(i.e. bypassing CISCO) and worked fine!! So, I need to set something up in CISCO but what? Do I have enable DHCP somehow?

[prerak_patel]

This is what I have:

interface FastEthernet3/1

switchport access vlan 21

!

interface FastEthernet3/2

switchport access vlan 21

!

interface FastEthernet3/3

switchport access vlan 21

interface Vlan21

description VLAN21-SIGTRAN-EXCEL

ip address 10.18.89.126 255.255.255.192

!

[prerak_patel]

Enabling portfast worked!!! But why?

Thanks for your help

[Roberto Salazar]

without portfast the port goes through the usual stages of spanning-tree, blocking, learning, forwarding. This stages is enough to cause start-up delay issues with DHCP, windows, Novell, Etc. with portfast the port is put in forwarding mode immediately upon connection.

[Roberto Salazar]

try putting in "spanning-tree portfast" under the interfaces where the client and server are connected as I earlier suggested.

[zahid Hamdani]

I have the same issue but bit different. My switch (c9300) as dhcp assign IPs to other devices but not assigning to AP c9105axi. I tried the spanning tree option but did not worked. any other solution? from logs the switch shows that i have release ip for the said AP but when I check in AP the AP shows I have no IP address. My AP can obtain IP from other DHCPs. the following is logs from switch side.....

Core-Switch-9300#

Apr 6 11:12:26.695:

-----Additional Debug------

Apr 6 11:12:26.695: DHCP process ID FFFFFFFFFFFFFFFF status 0

Apr 6 11:12:26.695: DHCP Network Discovery is disabled

Apr 6 11:12:26.695: DHCP NetDiscovery Informs 0 Discovers 0 Period 15

Apr 6 11:12:26.695: DHCPC HA status is Active

Apr 6 11:12:26.695: Checkpointing is Not active

Core-Switch-9300#sh ip dhcp server statistics

Memory usage 17771

Address pools 1

Database agents 0

Automatic bindings 1

Manual bindings 0

Expired bindings 0

Malformed messages 0

Secure arp entries 0

Renew messages 0

Workspace timeouts 0

Static routes 0

Relay bindings 0

Relay bindings active 0

Relay bindings terminated 0

Relay bindings selecting 0

Message Received

BOOTREQUEST 0

DHCPDISCOVER 58

DHCPREQUEST 8

DHCPDECLINE 0

DHCPRELEASE 0

DHCPINFORM 6

DHCPVENDOR 0

BOOTREPLY 0

DHCPOFFER 0

DHCPACK 0

DHCPNAK 0

Message Sent

BOOTREPLY 0

DHCPOFFER 30

DHCPACK 3

DHCPNAK 0

Message Forwarded

BOOTREQUEST 0

DHCPDISCOVER 0

DHCPREQUEST 0

DHCPDECLINE 0

DHCPRELEASE

Core-Switch-9300#sh ip dhcp binding

Bindings from all pools not associated with VRF:

IP address Client-ID/ Lease expiration Type State

Interface

Hardware address/

User name

10.10.20.101 0110.a829.01ff.b8 Apr 07 2023 04:09 PM Automatic

Active Vlan20

**********************************************************************************************************************

LOGS FROM AP

AP10A8.2901.FFB8#sh ip interface brief

Interface            IP-Address      Method   Status                 Protocol   Speed      Duplex

wired0               unassigned      unset    up                     up         1000       full

auxiliary-client     unassigned      unset    up                     up         n/a        n/a

apr0v0               n/a             n/a      administatively down   down       n/a        n/a

apr1v0               n/a             n/a      administatively down   down       n/a        n/a