dhcpd handing out wrong gateway

Fredrik Björk fredrik.bjork at fiberdata.se
Thu Sep 8 14:30:53 UTC 2011 

Hi!
 
We're having occasional problems with ISC dhcpd handing out an incorrect gateway (option routers) to some clients. This happens only for specific clients and is more or less persistent for those. The config is somewhat complicated and involves a few shared networks.
 
What happens is that a client in network 123.123.230.0/24 gets a correct IP, the appropriate subnet mask and all other options, but the gateway is 123.123.235.1, which is in a totally different subnet and even another shared network! Anybody with a clue about what's going on out there?
 
Just to give you a rough idea on the structure, I've filtered out a few lines from the config:
 
shared-network eth0{
        subnet 192.168.20.0 netmask 255.255.255.0 {
        subnet 123.123.224.0 netmask 255.255.255.0 {
        subnet 123.123.236.0 netmask 255.255.255.0 {

shared-network BSR1CM {
        subnet 172.16.0.0 netmask 255.255.252.0 {
        subnet 172.16.8.0 netmask 255.255.255.0 {
shared-network BSR1CPE {
        subnet 123.123.225.0 netmask 255.255.255.0 {
        subnet 123.123.226.0 netmask 255.255.255.128 {
        subnet 123.123.226.128 netmask 255.255.255.192 {
        subnet 123.123.226.192 netmask 255.255.255.224 {
shared-network BSR1MTA {
        subnet 123.123.226.224 netmask 255.255.255.224 {

shared-network BSR2CM {
        subnet 172.17.0.0 netmask 255.255.252.0 {
        subnet 172.17.4.0 netmask 255.255.252.0 {
        subnet 172.17.8.0 netmask 255.255.252.0 {
shared-network BSR2CPE {
        subnet 123.123.227.0 netmask 255.255.255.0 {
        subnet 123.123.228.0 netmask 255.255.255.128 {
        subnet 123.123.228.128 netmask 255.255.255.192 {
        subnet 123.123.228.192 netmask 255.255.255.224 {
        subnet 123.123.228.224 netmask 255.255.255.224 {
shared-network BSR2MTA {
        subnet 123.123.229.0 netmask 255.255.255.0 {

shared-network BSR3CM {
        subnet 172.18.0.0 netmask 255.255.252.0 {
        subnet 172.18.4.0 netmask 255.255.252.0 {
        subnet 172.18.8.0 netmask 255.255.252.0 {
shared-network BSR3CPE {
        subnet 123.123.230.0 netmask 255.255.255.0 {
        subnet 123.123.233.0 netmask 255.255.255.0 {
        subnet 123.123.231.0 netmask 255.255.255.0 {
shared-network BSR3MTA {
        subnet 123.123.232.0 netmask 255.255.255.0 {
        subnet 123.123.234.0 netmask 255.255.255.0 {

shared-network CASACM {
        subnet 172.19.0.0 netmask 255.255.240.0 {
shared-network CASACPE {
        subnet 123.123.235.0 netmask 255.255.255.0 {
        subnet 123.123.237.0 netmask 255.255.255.0 {
        subnet 123.123.238.0 netmask 255.255.255.0 {

 
14:29:20.933479 IP (tos 0x0, ttl 255, id 5252, offset 0, flags [none], proto UDP (17), length 344) 123.123.230.1.68 > 123.123.224.
42.67: BOOTP/DHCP, Request from 00:19:99:a0:51:13, length 316, hops 1, xid 0x39e50835, Flags [none]
          Gateway-IP 123.123.230.1
          Client-Ethernet-Address 00:19:99:a0:51:13
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Discover
            Client-ID Option 61, length 7: ether 00:19:99:a0:51:13
            Requested-IP Option 50, length 4: 123.123.233.232
            Hostname Option 12, length 12: "MyRouter"
            Vendor-Class Option 60, length 8: "MSFT 5.0"
            Parameter-Request Option 55, length 12:
              Subnet-Mask, Domain-Name, Default-Gateway, Domain-Name-Server
              Netbios-Name-Server, Netbios-Node, Netbios-Scope, Router-Discovery
              Static-Route, Classless-Static-Route, Classless-Static-Route-Microsoft, Vendor-Option
            Agent-Information Option 82, length 14:
              Unknown SubOption 2, length 6:
                0x0000:  0013 71e7 68ee
              Unknown SubOption 43, length 4:
                0x0000:  ac12 03f5
14:29:21.001405 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 335) 123.123.224.42.67 > 123.123.230.1.67:
 BOOTP/DHCP, Reply, length 307, hops 1, xid 0x39e50835, Flags [none]
          Your-IP 123.123.233.232
          Server-IP 123.123.224.42
          Gateway-IP 123.123.230.1
          Client-Ethernet-Address 00:19:99:a0:51:13
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Offer
            Server-ID Option 54, length 4: 123.123.224.42
            Lease-Time Option 51, length 4: 600
            Subnet-Mask Option 1, length 4: 255.255.255.0
            Domain-Name Option 15, length 11: "sweden.se"
            Default-Gateway Option 3, length 4: 123.123.235.1     <<<<----- WRONG!
            Domain-Name-Server Option 6, length 8: 213.50.29.170,208.67.222.222
            Agent-Information Option 82, length 14:
              Unknown SubOption 2, length 6:
                0x0000:  0013 71e7 68ee
              Unknown SubOption 43, length 4:
                0x0000:  ac12 03f5
14:29:21.016281 IP (tos 0x0, ttl 255, id 5256, offset 0, flags [none], proto UDP (17), length 364) 123.123.230.1.68 > 123.123.224.42.67: BOOTP/DHCP, Request from 00:19:99:a0:51:13, length 336, hops 1, xid 0x39e50835, Flags [none]
          Gateway-IP 123.123.230.1
          Client-Ethernet-Address 00:19:99:a0:51:13
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Request
            Client-ID Option 61, length 7: ether 00:19:99:a0:51:13
            Requested-IP Option 50, length 4: 123.123.233.232
            Server-ID Option 54, length 4: 123.123.224.42
            Hostname Option 12, length 12: "MyRouter"
            FQDN Option 81, length 15: "MyRouter"
            Vendor-Class Option 60, length 8: "MSFT 5.0"
            Parameter-Request Option 55, length 12:
              Subnet-Mask, Domain-Name, Default-Gateway, Domain-Name-Server
              Netbios-Name-Server, Netbios-Node, Netbios-Scope, Router-Discovery
              Static-Route, Classless-Static-Route, Classless-Static-Route-Microsoft, Vendor-Option
            Agent-Information Option 82, length 14:
              Unknown SubOption 2, length 6:
                0x0000:  0013 71e7 68ee
              Unknown SubOption 43, length 4:
                0x0000:  ac12 03f5
14:29:21.017506 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 335) 123.123.224.42.67 > 123.123.230.1.67: BOOTP/DHCP, Reply, length 307, hops 1, xid 0x39e50835, Flags [none]
          Your-IP 123.123.233.232
          Server-IP 123.123.224.42
          Gateway-IP 123.123.230.1
          Client-Ethernet-Address 00:19:99:a0:51:13
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: ACK
            Server-ID Option 54, length 4: 123.123.224.42
            Lease-Time Option 51, length 4: 600
            Subnet-Mask Option 1, length 4: 255.255.255.0
            Domain-Name Option 15, length 11: "sweden.se"
            Default-Gateway Option 3, length 4: 123.123.235.1
            Domain-Name-Server Option 6, length 8: 213.50.29.170,208.67.222.222
            Agent-Information Option 82, length 14:
              Unknown SubOption 2, length 6:
                0x0000:  0013 71e7 68ee
              Unknown SubOption 43, length 4:
                0x0000:  ac12 03f5

Any help is much appreciated!
 
/Fredrik
 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/dhcp-users/attachments/20110908/ff923c83/attachment.html>

More information about the dhcp-users mailing list