Wireless Access

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Occasional Contributor I

dhcp packets not relayed to external dhcp server (helper-address not working)

Hi,

 

I've configured a vlan to send dhcp packets to an external server

(momand) *[md] #show configuration effective detail santa | begin "interface vlan 107" 
interface vlan 107                                                               # local [/md/epicerie/00:1a:1e:03:8f:30]
    ip address 192.168.107.253 255.255.255.0                                     # local [/md/epicerie/00:1a:1e:03:8f:30]
    ip helper-address A.B.C.D                                              # local [/md/epicerie/00:1a:1e:03:8f:30]

 

when a client in this vlan ask for an IP address, all i have is:

 

Feb 13 10:59:03 santa CEF:0|Aruba|A72xx|68230|log|SystemEvent|3|deviceProcessName=dhcpd dvcpid=22412 dvchost=santa msg=<299801> <22412> <DBUG> \|dhcpd\|  DHCPDISCOVER from ac:87:a3:0a:c9:1f via eth1: unknown network segment
Feb 13 10:59:03 santa CEF:0|Aruba|A72xx|68230|log|SystemEvent|3|deviceProcessName=dhcpd dvcpid=22412 dvchost=santa msg=<299801> <22412> <DBUG> \|dhcpd\|  DHCPDISCOVER from ac:87:a3:0a:c9:1f via 192.168.107.253: unknown network segment

and no packets are sent to the unicast A.B.C.D address.

 

I'm fighting with this problem for days ...

any idea ?

 

 

 

Occasional Contributor I

Re: dhcp packets not sent to external dhcp server

More information:

I use the internal dhcp server for another vlan

(santa) #show ip dhcp database

DHCP enabled

# vlan_5
subnet 192.168.4.0 netmask 255.255.252.0 {
	option vendor-class-identifier  "ArubaAP";
	option vendor-encapsulated-options  "xx.xx.xx.xx";
	option domain-name-servers B.C.D.E;
	option routers 192.168.5.254;
	range 192.168.4.1 192.168.5.253;
	range 192.168.5.255 192.168.7.254;
	authoritative;
} 

 

Occasional Contributor I

Re: dhcp packets not sent to external dhcp server

No idea ?

 

How could I debug the dhcp-relay (helper) process ?

 

Occasional Contributor I

Re: dhcp packets not sent to external dhcp server

Solved !

A dhcp snooping bug in an HP 5900 switch in the middle :-(

 

packet-capture was my best friend to find it ...

 

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