DHCP issue for IP Phones ,DHCP configured on local switch

[vasanth77]

Hi,

I'm facing DHCP issue for the IP phones which are showing configuring IP mode and not getting IP's ,after clearing DHCP BINDINGS on local switch  some phones are getting IP and not all phones.

Switch reboot fixed this issue but don't know the root cause.

I debuged the DHCP events and it's statistics

can anybody identify what is actuall happened in my switch

Finally we rebooted the switch then all phones are got IP and registered and working fine.below the logs

8 switches stacked in a single stack with the same model enabled DHCP for voice vlan(vlan100) locally and

data VLAN is from global IPAM server outside the LAN

WS-C3750-48P       12.2(25)SEB4            C3750-IPBASE-M 

10.178.50.177 - Global IPAM server

10.33.168.1     - Stack switch Ip address and also Data VLAN(vlan2) IP address 

Before rebooting

1703808: Oct 27 17:53:49.632: DHCPD: BOOTREQUEST from 0100.1646.ea9d.ea forwarded to 10.178.50.177.

1703809: Oct 27 17:53:49.683: DHCPD: forwarding BOOTREPLY to client 0016.46ea.9dea.

1703810: Oct 27 17:53:49.683: DHCPD: Forwarding reply on numbered intf

1703811: Oct 27 17:53:49.683: DHCPD: broadcasting BOOTREPLY to client 0016.46ea.9dea.

1703812: Oct 27 17:53:49.708: DHCPD: DHCPREQUEST received from client 0100.1646.ea9d.ea.

1703813: Oct 27 17:53:49.708: DHCPD: setting giaddr to 10.33.168.1.

1703814: Oct 27 17:53:49.708: DHCPD: BOOTREQUEST from 0100.1646.ea9d.ea forwarded to 10.178.50.177.

1703815: Oct 27 17:53:49.775: DHCPD: forwarding BOOTREPLY to client 0016.46ea.9dea.

1703816: Oct 27 17:53:49.775: DHCPD: Forwarding reply on numbered intf

1703817: Oct 27 17:53:49.775: DHCPD: broadcasting BOOTREPLY to client 0016.46ea.9dea.

1703818: Oct 27 17:53:49.834: DHCPD: DHCPDISCOVER received from client 0100.1646.eaa0.f9 on interface Vlan2.

1703819: Oct 27 17:53:49.834: DHCPD: there is no address pool for 10.33.168.1.

1703820: Oct 27 17:53:49.834: DHCPD: setting giaddr to 10.33.168.1.

1703821: Oct 27 17:53:49.834: DHCPD: BOOTREQUEST from 0100.1646.eaa0.f9 forwarded to 10.178.50.177.

1703822: Oct 27 17:53:50.060: DHCPD: DHCPDISCOVER received from client 0100.1646.acf3.ab on interface Vlan2.

1703823: Oct 27 17:53:50.060: DHCPD: there is no address pool for 10.33.168.1.

1703824: Oct 27 17:53:50.060: DHCPD: setting giaddr to 10.33.168.1.

1703825: Oct 27 17:53:50.060: DHCPD: BOOTREQUEST from 0100.1646.acf3.ab forwarded to 10.178.50.177.

1703826: Oct 27 17:53:50.119: DHCPD: DHCPDISCOVER received from client 016c.9989.8407.d3 on interface Vlan2.

1703827: Oct 27 17:53:50.119: DHCPD: there is no address pool for 10.33.168.1.

1703828: Oct 27 17:53:50.119: DHCPD: setting giaddr to 10.33.168.1.

1703829: Oct 27 17:53:50.119: DHCPD: BOOTREQUEST from 016c.9989.8407.d3 forwarded to 10.178.50.177.

1703830: Oct 27 17:53:50.278: DHCPD: DHCPDISCOVER received from client 0100.1646.eaa2.cf on interface Vlan2.

1703831: Oct 27 17:53:50.278: DHCPD: there is no address pool for 10.33.168.1.

1703832: Oct 27 17:53:50.278: DHCPD: setting giaddr to 10.33.168.1.

1703833: Oct 27 17:53:50.278: DHCPD: BOOTREQUEST from 0100.1646.eaa2.cf forwarded to 10.178.50.177.

1703834: Oct 27 17:53:50.312: DHCPD: DHCPDISCOVER received from client 0100.16c7.2911.e9 on interface Vlan2.

1703835: Oct 27 17:53:50.312: DHCPD: there is no address pool for 10.33.168.1.

1703836: Oct 27 17:53:50.312: DHCPD: setting giaddr to 10.33.168.1.

1703837: Oct 27 17:53:50.312: DHCPD: BOOTREQUEST from 0100.16c7.2911.e9 forwarded to 10.178.50.177.

1703838: Oct 27 17:53:50.312: DHCPD: DHCPDISCOVER received from client 0100.1646.ea9f.96 on interface Vlan2.

1703839: Oct 27 17:53:50.312: DHCPD: there is no address pool for 10.33.168.1.

1703840: Oct 27 17:53:50.312: DHCPD: setting giaddr to 10.33.168.1.

1703841: Oct 27 17:53:50.320: DHCPD: BOOTREQUEST from 0100.1646.ea9f.96 forwarded to 10.178.50.177.

1703842: Oct 27 17:53:50.329: DHCPD: forwarding BOOTREPLY to client 0016.46ea.a2cf.

1703843: Oct 27 17:53:50.329: DHCPD: Forwarding reply on numbered intf

1703844: Oct 27 17:53:50.329: DHCPD: broadcasting BOOTREPLY to client 0016.46ea.a2cf.

1703845: Oct 27 17:53:50.345: DHCPD: DHCPREQUEST received from client 0100.1646.eaa2.cf.

1703846: Oct 27 17:53:50.345: DHCPD: setting giaddr to 10.33.168.1.

1703847: Oct 27 17:53:50.345: DHCPD: BOOTREQUEST from 0100.1646.eaa2.cf forwarded to 10.178.50.177.

1703848: Oct 27 17:53:50.371: DHCPD: DHCPDISCOVER received from client 0100.16c7.2911.98 on interface Vlan2.

1703849: Oct 27 17:53:50.371: DHCPD: there is no address pool for 10.33.168.1.

1703850: Oct 27 17:53:50.371: DHCPD: setting giaddr to 10.33.168.1.

1703851: Oct 27 17:53:50.371: DHCPD: BOOTREQUEST from 0100.16c7.2911.98 forwarded to 10.178.50.177.

1703852: Oct 27 17:53:50.371: DHCPD: forwarding BOOTREPLY to client 0016.46ea.9f96.

1703853: Oct 27 17:53:50.371: DHCPD: Forwarding reply on numbered intf

1703854: Oct 27 17:53:50.371: DHCPD: broadcasting BOOTREPLY to client 0016.46ea.9f96.

1703855: Oct 27 17:53:50.387: DHCPD: DHCPREQUEST received from client 0100.1646.ea9f.96.

1703856: Oct 27 17:53:50.387: DHCPD: setting giaddr to 10.33.168.1.

1703857: Oct 27 17:53:50.387: DHCPD: BOOTREQUEST from 0100.1646.ea9f.96 forwarded to 10.178.50.177.

1703858: Oct 27 17:53:50.396: DHCPD: forwarding BOOTREPLY to client 0016.46ea.a2cf.

1703859: Oct 27 17:53:50.396: DHCPD: Forwarding reply on numbered intf

1703860: Oct 27 17:53:50.396: DHCPD: broadcasting BOOTREPLY to client 0016.46ea.a2cf.

1703861: Oct 27 17:53:50.396: DHCPD: DHCPDISCOVER received from client 0100.1647.57e6.1f on interface Vlan2.

1703862: Oct 27 17:53:50.396: DHCPD: there is no address pool for 10.33.168.1.

1703863: Oct 27 17:53:50.404: DHCPD: setting giaddr to 10.33.168.1.

1703864: Oct 27 17:53:50.404: DHCPD: BOOTREQUEST from 0100.1647.57e6.1f forwarded to 10.178.50.177.

1703865: Oct 27 17:53:50.421: DHCPD: DHCPDISCOVER received from client 0100.1647.184e.d5 on interface Vlan2.

1703866: Oct 27 17:53:50.421: DHCPD: there is no address pool for 10.33.168.1.

1703867: Oct 27 17:53:50.421: DHCPD: setting giaddr to 10.33.168.1.

1703868: Oct 27 17:53:50.421: DHCPD: BOOTREQUEST from 0100.1647.184e.d5 forwarded to 10.178.50.177.

1703869: Oct 27 17:53:50.429: DHCPD: forwarding BOOTREPLY to client 0016.46ea.9f96.

1703870: Oct 27 17:53:50.429: DHCPD: Forwarding reply on numbered intf

1703871: Oct 27 17:53:50.429: DHCPD: broadcasting BOOTREPLY to client 0016.46ea.9f96.

1703872: Oct 27 17:53:50.471: DHCPD: DHCPDISCOVER received from client 0100.1647.48d0.c8 on interface Vlan2.

1703873: Oct 27 17:53:50.471: DHCPD: there is no address pool for 10.33.168.1.

1703874: Oct 27 17:53:50.471: DHCPD: setting giaddr to 10.33.168.1.

1703875: Oct 27 17:53:50.471: DHCPD: BOOTREQUEST from 0100.1647.48d0.c8 forwarded to 10.178.50.177.

1703876: Oct 27 17:53:50.471: DHCPD: forwarding BOOTREPLY to client 0016.4718.4ed5.

1703877: Oct 27 17:53:50.471: DHCPD: Forwarding reply on numbered intf

1703878: Oct 27 17:53:50.471: DHCPD: broadcasting BOOTREPLY to client 0016.4718.4ed5.

1703879: Oct 27 17:53:50.488: DHCPD: DHCPREQUEST received from client 0100.1647.184e.d5.

1703880: Oct 27 17:53:50.488: DHCPD: setting giaddr to 10.33.168.1.

1703881: Oct 27 17:53:50.488: DHCPD: BOOTREQUEST from 0100.1647.184e.d5 forwarded to 10.178.50.177.

1703882: Oct 27 17:53:50.530: DHCPD: forwarding BOOTREPLY to client 0016.4718.4ed5.

1703883: Oct 27 17:53:50.530: DHCPD: Forwarding reply on numbered intf

1703884: Oct 27 17:53:50.530: DHCPD: broadcasting BOOTREPLY to client 0016.4718.4ed5.

1703885: Oct 27 17:53:50.614: DHCPD: DHCPDISCOVER received from client 0100.16c7.b755.4f on interface Vlan2.

1703886: Oct 27 17:53:50.614: DHCPD: there is no address pool for 10.33.168.1.

1703887: Oct 27 17:53:50.614: DHCPD: setting giaddr to 10.33.168.1.

1703888: Oct 27 17:53:50.614: DHCPD: BOOTREQUEST from 0100.16c7.b755.4f forwarded to 10.178.50.177.

1703889: Oct 27 17:53:50.647: DHCPD: DHCPDISCOVER received from client 0100.1646.ef87.75 on interface Vlan2.

1703890: Oct 27 17:53:50.647: DHCPD: there is no address pool for 10.33.168.1.

1703891: Oct 27 17:53:50.647: DHCPD: setting giaddr to 10.33.168.1.

1703892: Oct 27 17:53:50.647: DHCPD: BOOTREQUEST from 0100.1646.ef87.75 forwarded to 10.178.50.177.

1703893: Oct 27 17:53:50.673: DHCPD: forwarding BOOTREPLY to client 0016.c7b7.554f.

1703894: Oct 27 17:53:50.673: DHCPD: Forwarding reply on numbered intf

1703895: Oct 27 17:53:50.673: DHCPD: broadcasting BOOTREPLY to client 0016.c7b7.554f.

1703896: Oct 27 17:53:50.689: DHCPD: DHCPREQUEST received from client 0100.16c7.b755.4f.

1703897: Oct 27 17:53:50.689: DHCPD: setting giaddr to 10.33.168.1.

1703898: Oct 27 17:53:50.698: DHCPD: BOOTREQUEST from 0100.16c7.b755.4f forwarded to 10.178.50.177.

1703899: Oct 27 17:53:50.740: DHCPD: forwarding BOOTREPLY to client 0016.c7b7.554f.

1703900: Oct 27 17:53:50.740: DHCPD: Forwarding reply on numbered intf

1703901: Oct 27 17:53:50.740: DHCPD: broadcasting BOOTREPLY to client 0016.c7b7.554f.

1703902: Oct 27 17:53:50.790: DHCPD: DHCPDISCOVER received from client 0100.1646.ea9f.97 on interface Vlan2.

1703903: Oct 27 17:53:50.790: DHCPD: there is no address pool for 10.33.168.1.

LPGBLPL04S001#show ip dhcp server statistics
Memory usage 7484
Address pools 1
Database agents 0
Automatic bindings 18
Manual bindings 0
Expired bindings 0
Malformed messages 0

Message Received
BOOTREQUEST 0
DHCPDISCOVER 32500
DHCPREQUEST 5333
DHCPDECLINE 2126
DHCPRELEASE 245
DHCPINFORM 109

Message Sent
BOOTREPLY ? 0
DHCPOFFER 82
DHCPACK 88
DHCPNAK 24

++++++++++++++++++++++++++++++++++++++++

After Rebooting

LPGBLPL04S001#show ip dhcp server statistics
Memory usage 17750
Address pools 1
Database agents 0
Automatic bindings 136
Manual bindings 0
Expired bindings 52
Malformed messages 3

Message Received
BOOTREQUEST 0
DHCPDISCOVER 849
DHCPREQUEST 1018
DHCPDECLINE 1
DHCPRELEASE 1
DHCPINFORM 268

Message Sent
BOOTREPLY 0
DHCPOFFER 336
DHCPACK 364

can anybody says why the DHCP DECLINE happening

the lease time for our scope is 7 days- is this a problem causing?

Can anybody tell me the root cause ?

after reboot it is fixed . Now the phones are getting IP address and working fine ,but wanted to know what caused this to go wrong.

thanks in advance

vasanth

[Francesco Molino]

Hi

A detailed explanation of dhcp decline event:

Before a Cisco DHCP server give an IP address to a client, it always ARPs and pings the address to make sure it's not used. 

If it gets a response then the Cisco DHCP server set this IP as a conflict and place this IP into its conflict table.

If it didn't get a response it serve the client with this IP. The client will send a gratuitous ARP with its new IP address. If not reply then everything is ok. However if it does receive a reply on its gratuitous ARP message, it will indicate that another host is using that address and send DECLINE message to the DHCP server, rejecting the IP address assigned. THe Cisco dhcp server (as it saw the 2 gratuitous arp msg) will move this IP in its conflict table and assign the next available IP address to the client.

However I don't see the message in your debugs that the pool is empty which is related usually to the decline message. But I see this message:

DHCPD: there is no address pool for 10.33.168.1.

This is the subnet of your dhcp right? What's the dhcp pool config?

To avoid conflict and then decline message, I recommend to use 1 of those 2 commands:

- ip dhcp database url [timeout seconds | write-delay seconds]

- no ip dhcp conflict logging

Here the Cisco documentation: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_dhcp/configuration/15-mt/dhcp-15-mt-book/config-dhcp-server.html

Thanks

PS: Please don't forget to rate and mark as correct answer if this answered your question.

[vasanth77]

Hi friend,

10.33.168.1 - this IP is the mgmt VLAN ip of the switch 

for this scenario we have configured Voice VLAN 100 DHCP scope locally on the switch 

For VLAN 2 is date which is configured to glopal IPAM server IP by using ip helper address

I already mentioned  a single reboot of switch solved the issue without configuring anything,

that why I'm asking.

So any one of the command below will reduce the DECLINE  msg

Thanks for you quick reply 

Regards,

Vasanth R

[Francesco Molino]

Hi

maybe I missed something on your first message sorry. 

Do you have a dhcp config on your switch? If you DECLINE msg it means that this switch is acting as dhcp server or was acting if a config was made but not saved. This explains maybe why you're not facing the issue after the reload. 

If your dhcp is a 3rd party device, the command I sent won't correct the issue. 

Thanks