Troubleshooting

DHCP Not Assigning IP Addresses on a Cisco Router

VSVipul Sir · 6 min readLast updated: 22 July 2026

A client showing 169.254.x.x (APIPA) never received a DHCP offer. On a Cisco router the usual causes are a pool whose network does not match the interface subnet, the gateway address not being excluded, or the DHCP server being on another subnet with no ip helper-address configured.

What you see

PC> ipconfig
IPv4 Address. . . . . . . . . . . : 169.254.213.44
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

Why it happens

DHCP begins with a broadcast (DISCOVER). Routers do not forward broadcasts, so if the server is on a different subnet the request never arrives — that is what ip helper-address solves, by converting the broadcast to a unicast toward the server.

When the router itself is the server, the pool's network statement must match the subnet of the interface receiving the request. If it does not, the router has no matching pool and stays silent. Forgetting ip dhcp excluded-address is also common: the router hands out its own gateway address to a client, causing a duplicate-IP conflict.

How to confirm it

show ip dhcp pool
show ip dhcp binding
show ip dhcp conflict
debug ip dhcp server events

show ip dhcp pool shows how many addresses are leased and whether the pool is exhausted. Empty bindings with clients complaining means requests are not arriving at all — suspect the relay.

The fix

! Exclude the addresses you use statically FIRST
ip dhcp excluded-address 192.168.10.1 192.168.10.10
!
ip dhcp pool LAN10
 network 192.168.10.0 255.255.255.0
 default-router 192.168.10.1
 dns-server 8.8.8.8
 lease 7
!
! If the server is on another subnet, relay from the client-side interface
interface GigabitEthernet0/0.10
 ip helper-address 192.168.50.5

ip helper-address goes on the interface facing the clients, pointing at the server — a very common mix-up is configuring it on the server side instead.

How to stop it happening again

Always exclude your static range before creating the pool, and keep gateway/DNS/server addresses inside that excluded block.

Questions people ask

What does a 169.254 address mean?

It is APIPA — the client self-assigned because no DHCP server answered. It always indicates a DHCP delivery problem, never a bad pool size.

Do I need ip helper-address if the router is the DHCP server?

No. Helper addresses are only for relaying to a server on a different subnet. If the router owns the pool, it answers directly.

Reading the fix is not the same as doing it

Every fault on this page can be broken and repaired on real Cisco routers and switches in our Ahmedabad lab — which is how it stops being theory. Come and see the rack before you pay anything.