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Thread: Help with DHCP

  1. Senior Member
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    #1

    Default Help with DHCP

    I have a problme with one of our brandches. The user is not able to get a IP Address from a DHCP Server that it is configure on one switch.

    here is the debug output
    Code:
    Jun  1 09:29:00.981 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:29:00.981 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:29:00.981 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:29:00.981 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:29:00.981 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:29:04.974 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:29:04.974 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:29:04.974 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:29:04.974 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:29:04.974 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:29:12.985 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:29:12.985 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:29:12.985 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:29:12.985 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:29:12.985 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:29:28.974 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:29:28.974 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:29:28.974 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:29:28.974 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:29:28.974 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:29:37.262 EDT: DHCPD: checking for expired leases.
    Jun  1 09:30:45.320 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:30:45.320 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:30:45.320 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:30:45.320 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:30:45.320 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:30:49.304 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:30:49.304 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:30:49.304 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:30:49.304 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:30:49.304 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:30:57.760 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:30:57.760 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:30:57.760 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:30:57.760 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:30:57.760 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:31:13.329 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:31:13.329 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:31:13.329 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:31:13.329 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:31:13.329 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:31:48.981 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:31:48.981 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:31:48.981 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:31:48.981 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:31:48.981 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:31:51.984 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:31:51.984 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:31:51.984 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:31:51.984 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:31:51.984 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:31:58.989 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:31:58.989 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:31:58.989 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:31:58.989 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:31:58.989 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:32:13.988 EDT: DHCPD: DHCPDISCOVER received from client 0100.1cbf.1d0b.f6 on interface Vlan67.
    Jun  1 09:32:13.988 EDT: DHCPD: requested address 169.254.206.232 is not on subnet 172.19.9.8.
    Jun  1 09:32:13.988 EDT: DHCPD: address pool DM_Access is empty.
    Jun  1 09:32:13.988 EDT: DHCPD: setting giaddr to 172.19.9.10.
    Jun  1 09:32:13.988 EDT: DHCPD: BOOTREQUEST from 0100.1cbf.1d0b.f6 forwarded to 172.19.9.12.
    Jun  1 09:33:37.279 EDT: DHCPD: checking for expired leases.
    Jun  1 09:35:37.287 EDT: DHCPD: checking for expired leases.
    Here is the config:

    Code:
    ip domain-name corp.company.com
    ip dhcp excluded-address 172.19.9.9 172.19.9.12
    !
    ip dhcp pool DM_Access
       network 172.19.9.8 255.255.255.248
       dns-server 172.20.50.215 172.20.50.217 
       default-router 172.19.9.9 
       domain-name corp.company.com
       lease 0 2
    !
    I know that I have only two ip avalaible and it design to work like that. Thanks in advance
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  3. Went to the dark side.... Moderator networker050184's Avatar
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    #2
    Looks like its trying to request an invalid address to me. Have you tried a release on the host?
    Last edited by networker050184; 06-01-2011 at 03:10 PM.
    An expert is a man who has made all the mistakes which can be made.
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    #3
    It says your pool is empty (which would mean all of the addresses are already taken)

    Try these two commands:

    1. sh ip dhcp binding (this should tell you what is taking up the addresses)
    2. sh ip dhcp pool DM_Access (this should give you summary information on the pool)

    Source:
    Cisco IOS IP Addressing Services Configuration Guide, Release 12.4 - Configuring the Cisco IOS DHCP Server [Cisco IOS Software Releases 12.4 Mainline] - Cisco Systems

    ^^^ Use this document, to give further troubleshooting assistance.
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  5. Senior Member
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    #4
    Quote Originally Posted by instant000 View Post
    It says your pool is empty (which would mean all of the addresses are already taken)

    Try these two commands:

    1. sh ip dhcp binding (this should tell you what is taking up the addresses)
    2. sh ip dhcp pool DM_Access (this should give you summary information on the pool)

    Source:
    Cisco IOS IP Addressing Services Configuration Guide, Release 12.4 - Configuring the Cisco IOS DHCP Server [Cisco IOS Software Releases 12.4 Mainline] - Cisco Systems

    ^^^ Use this document, to give further troubleshooting assistance.
    I try sh ip dhcp binding and it is empty, I try sh ip dhcp pool DM_Acess, but that command is not available.
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  6. Senior Member
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    #5
    Quote Originally Posted by networker050184 View Post
    Looks like its trying to request an invalid address to me. Have you tried a release on the host?
    Yes, several times.
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    #6
    Please post the full config. Looks like there's some dhcp forwarding going on. udp-helper?


    Also, what kind of machine is 172.19.9.12? What does the config look like on that machine?
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    #7
    Quote Originally Posted by creamy_stew View Post
    Please post the full config. Looks like there's some dhcp forwarding going on. udp-helper?


    Also, what kind of machine is 172.19.9.12? What does the config look like on that machine?
    Update: It looks like that every request is send out to 172.19.9.12 to get an IP from 172.19.9.12, the thing is that .12 doesn't have a DHCP server. The DHCP server is located in one switch and for some reason the person that was working here before had a ip helper pointing to that dirrection. Also, I don't know ho wcan that effect because the client is in the same vlan as the dhcp server and I don't why is using the IP helper (If that is the problem). We have the same setup in our lab and it is woring fine. Right now I can't troubleshoot this issue because there is nobody at that branch, but I will next Monday, so I will update my finding and hope I get it resolve. Thanks
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  9. He Hate Me Zartanasaurus's Avatar
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    #8
    Quote Originally Posted by amb1s1 View Post
    Also, I don't know ho wcan that effect because the client is in the same vlan as the dhcp server and I don't why is using the IP helper (If that is the problem).
    DHCP Discovers and Requests are broadcasts. ip helper-address takes the broadcast and unicasts it to the configured ip(s). So even if you have a DHCP server on the same VLAN, the SVI is still going to see the broadcast and assume it has work to do.

    The weird thing is, it's requesting an APIPA address. APIPA requests are handled by ARP, so you wouldn't expect to see that as a DHCP request. It's almost as if there's a rogue DHCP server on the network configured to hand out APIPA addresses, the client is receiving an offer from that rogue server, then the client is broadcasting a request which the SVI sees and forwards to the ip helper-address, which generates the error message.

    At any rate, you can no out the ip helper-address on that SVI.
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