I have been trying to set up a 2514 as a NAT firewall on my ATT cable connection to replace a win 2k server set up with ICS. I happened to have a spare 2514 with ios 12.2 so I thought I would try to use the more recent NAT capabilities.
Eth0 is connected to the internal network with 192.168.0.10 as its IP and I have an internal DHCP server to give out IP to my LAN pcs in the range 192.168.0.11 to 192.168.0.200.
ETh 1 is connected to the 3com cable modem ATT provides. Now, the old setup simply used DHCP from the win2k to the cable modem and I initially copied the MAC address, DNS servers, gateway and IP address the win2k box had into the 2514 config and ethernet 1 interface settings and all was fine. My internal LAN was working, connected to the internet and the dynamic config of NAT I had setup seemed to work fine. Mail flows in and out and I can browse the internet.
Knowing that DHCP was used by the cable provider for a reason I thought I would try and configure the eth 1 interface to use DHCP instead of the static IP I 'extracted' from the win2k box. So I reloaded a config and simply replaced one line AND rebooted, The eth 1 interface went from
(which works) to
and it did not work at all. Anyone got any idea how the router thinks the offered address overlaps as shown in the dbeug at the end of this post? Its got me stumped. I am a newbie to the cisco routers and IOS so be kind
. On enabling debug I see the following and it simply does not make sense, I made a point of completely reloading the router and even power cycling to be sure that nothing was hanging around and I always see the same result:
Eth0 is connected to the internal network with 192.168.0.10 as its IP and I have an internal DHCP server to give out IP to my LAN pcs in the range 192.168.0.11 to 192.168.0.200.
ETh 1 is connected to the 3com cable modem ATT provides. Now, the old setup simply used DHCP from the win2k to the cable modem and I initially copied the MAC address, DNS servers, gateway and IP address the win2k box had into the 2514 config and ethernet 1 interface settings and all was fine. My internal LAN was working, connected to the internet and the dynamic config of NAT I had setup seemed to work fine. Mail flows in and out and I can browse the internet.
Knowing that DHCP was used by the cable provider for a reason I thought I would try and configure the eth 1 interface to use DHCP instead of the static IP I 'extracted' from the win2k box. So I reloaded a config and simply replaced one line AND rebooted, The eth 1 interface went from
Code:
...
mac-address 0010.5a05.4c37
ip address 66.31.136.15 255.255.248.0
...(which works) to
Code:
...
mac-address 0010.5a05.4c37
ip address dhcp
...and it did not work at all. Anyone got any idea how the router thinks the offered address overlaps as shown in the dbeug at the end of this post? Its got me stumped. I am a newbie to the cisco routers and IOS so be kind
. On enabling debug I see the following and it simply does not make sense, I made a point of completely reloading the router and even power cycling to be sure that nothing was hanging around and I always see the same result:
Code:
05:13:52: DHCP: allocate request
05:13:52: DHCP: new entry. add to queue
05:13:52: DHCP: SDiscover attempt # 1 for entry:
05:13:52: Temp IP addr: 0.0.0.0 for peer on Interface: Ethernet1
05:13:52: Temp sub net mask: 0.0.0.0
05:13:52: DHCP Lease server: 0.0.0.0, state: 1 Selecting
05:13:52: DHCP transaction id: 732
05:13:52: Lease: 0 secs, Renewal: 0 secs, Rebind: 0 secs
05:13:52: Next timer fires after: 00:00:02
05:13:52: Retry count: 1 Client-ID: cisco-0010.5a05.4c37-Et1
05:13:52: DHCP: SDiscover: sending 308 byte length DHCP packet
05:13:52: DHCP: SDiscover 308 bytes
05:13:52: B'cast on Ethernet1 interface from 0.0.0.0
05:13:52: DHCP: Received a BOOTREP pkt
05:13:52: DHCP: Scan: Message type: DHCP Offer
05:13:52: DHCP: Scan: Lease Time: 274539
05:13:52: DHCP: Scan: Server ID Option: 24.147.2.140 = 1893028C
05:13:52: DHCP: rcvd pkt source: 24.147.2.140, destination: 255.255.255.255
05:13:52: UDP sport: 43, dport: 44, length: 556
05:13:52: DHCP op: 2, htype: 1, hlen: 6, hops: 0
05:13:52: DHCP server identifier: 24.147.2.140
05:13:52: xid: 732, secs: 0, flags: 8000
05:13:52: client: 0.0.0.0, your: 66.31.136.15
05:13:52: srvr: 0.0.0.0, gw: 66.31.136.1
05:13:52: options block length: 308
05:13:52: DHCP Offer Message Offered Address: 66.31.136.15
05:13:52: DHCP: Lease Seconds: 274539
05:13:52: DHCP: Server ID Option: 24.147.2.140
05:13:52: DHCP: offer received from 24.147.2.140
05:13:52: DHCP: offered address overlaps with another interface.punt