Akagra

• 64-bit Ubuntu Intrepid 8.10
• 2 x NIC
• Both configured via DHCP
• eth0 goes to a LAN (10.5.5.0/24)
• eth1 goes to the Internet.

Problem:

• When both NICs are up I can’t get to the Internet.
• The issue is that both DHCP clients were requesting default gateway info and so I had two default gateway entries in my routing table.

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.59.3.0 * 255.255.255.0 U 0 0 0 eth1
10.5.5.0 * 255.255.255.0 U 0 0 0 eth0
192.168.122.0 * 255.255.255.0 U 0 0 0 vnet0
link-local * 255.255.0.0 U 1000 0 0 eth0
default 10.59.3.1 0.0.0.0 UG 100 0 0 eth1
default 10.5.5.1 0.0.0.0 UG 100 0 0 eth0

Solution:

• Modify the /etc/dhcp3/dhclients.conf file.
• Add an interface section for each NIC and don’t request a router for the LAN-side.

interface “eth0″ {
request subnet-mask, broadcast-address, time-offset, domain-name-servers,
domain-name, domain-search, host-name, interface-mtu;
}

interface “eth1″ {
request subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-search, host-name,
netbios-name-servers, netbios-scope, interface-mtu;
}

note: I am also using my own DNS server so I don’t request one from eth1.