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Marvin de Haas
Beginner

DHCP relay not working

dear all,

 

I am trying to configure DHCP relay by using ip helper addresses. Strange enough I configured the ip helper addresses properly but the DHCP requests are not being forwarded. Very strange this behavior. I configured it on other similar devices exactly the same, but on this device it is not working.

When I debug the DHCP broadcast a see a strange message about;

00:14:01: FIBipv4-packet-proc: route packet from Vlan1 src 0.0.0.0 dst 255.255.255.255
00:14:01: FIBfwd-proc: Default:255.255.255.255/32 receive entry
00:14:01: FIBipv4-packet-proc: packet routing failed
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 360, rcvd 2
00:14:01: UDP src=68, dst=67
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 360, stop process pak for forus packet

http://www.cisco.com/c/en/us/support/docs/ip/dynamic-address-allocation-resolution/27470-100.html

I really don't understand why the DHCP broadcast is not being forwarded. There is no ACL configured on the gateway. IP routing is enabled. Also I did an ping request from the gateways IP address to the DNS IP destination succesfully so routing is no issue at all.

The configuration is as follows;

interface Vlan1
 ip address 192.168.27.254 255.255.255.0
 ip helper-address 10.234.66.140
 ip helper-address 10.234.66.141
 ip helper-address 10.234.66.146
!
interface Vlan3
 ip address 10.1.65.254 255.255.255.0
 ip helper-address 10.234.66.140
 ip helper-address 10.234.66.141
 ip helper-address 192.168.27.24
!
interface Vlan10
 ip address 10.1.67.254 255.255.255.0
 ip helper-address 10.234.66.140
 ip helper-address 10.234.66.141
 ip helper-address 192.168.27.24
!
interface Vlan11
 ip address 10.1.68.254 255.255.255.0
 ip helper-address 10.234.66.140
 ip helper-address 10.234.66.141
 ip helper-address 192.168.27.24
 

Only the vlan 1 is not working properly with DHCP relay, but the rest is working fine.

Does someone have any idea what is going on here?

 

E, sendself FALSE, mtu 0, fwdchk FALSE pak 492D990 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 554AD2C consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 553CD64 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 4920F70 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 553DF70 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 492217C consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 553F518 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 55411F8 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 4925068 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 5542068 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 4925ED8 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 4926610 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 347, input feature
00:14:01:     UDP src=68, dst=67, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE
00:14:01: FIBipv4-packet-proc: route packet from Vlan1 src 0.0.0.0 dst 255.255.255.255
00:14:01: FIBfwd-proc: Default:255.255.255.255/32 receive entry
00:14:01: FIBipv4-packet-proc: packet routing failed
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 347, rcvd 2
00:14:01:     UDP src=68, dst=67
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 347, stop process pak for forus packet
00:14:01:     UDP src=68, dst=67
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 347, input feature
00:14:01:     UDP src=68, dst=67, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE
00:14:01: FIBipv4-packet-proc: route packet from Vlan1 src 0.0.0.0 dst 255.255.255.255
00:14:01: FIBfwd-proc: Default:255.255.255.255/32 receive entry
00:14:01: FIBipv4-packet-proc: packet routing failed
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 347, rcvd 2
00:14:01:     UDP src=68, dst=67
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 347, stop process pak for forus packet
00:14:01:     UDP src=68, dst=67
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 360, input feature
00:14:01:     UDP src=68, dst=67, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE
00:14:01: FIBipv4-packet-proc: route packet from Vlan1 src 0.0.0.0 dst 255.255.255.255
00:14:01: FIBfwd-proc: Default:255.255.255.255/32 receive entry
00:14:01: FIBipv4-packet-proc: packet routing failed
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 360, rcvd 2
00:14:01:     UDP src=68, dst=67
00:14:01: IP: s=0.0.0.0 (Vlan1), d=255.255.255.255, len 360, stop process pak for forus packet
00:14:01:     UDP src=68, dst=67pak 5544BB8 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE pak 4929898 consumed in input feature , packet consumed, MCI Check(63), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE
 

17 REPLIES 17

Most of the times DHCP Relays does not work because people forgets to enable the DHCP service in the global configuration of the network device:

Try this:

conf t

service dhcp

http://www.cisco.com/en/US/docs/ios/12_4t/ip_addr/configuration/guide/htdhcpre.html

PPrerequisites for Configuring the Cisco IOS DHCP Relay Agent

Before you configure the DHCP relay agent, you should understand the concepts documented in the "DHCP Overview" module.

The Cisco IOS DHCP server and relay agent are enabled by default. You can verify if they have been disabled by checking your configuration file. If they have been disabled, the no service dhcp command will appear in the configuration file. Use the service dhcp command to reenable the functionality if necessary.

The Cisco IOS DHCP relay agent will be enabled on an interface only when the ip helper-address is configured. This command enables the DHCP broadcast to be forwarded to the configured DHCP server.

I do face the same issue

For me, the setup is working properly and suddenly goes off, during the time i can't see any relay packet from SVI to DHCP server. This issue is for only one SVI, all other are working.

I am using 3850 box with Image: cat3k_caa-universalk9 SW ver: 03.03.05SE

AbteenZ
Beginner

I've seen routers with this problem a lot. Two workarounds always worked for me.

 

Enabling and disabling service dhcp few times.

service dhcp
no service dhcp

also removing the ip helper-address or adding other dhcp servers in your environment.

 

Hope this helps.