Your current routing table shows eth0 with static configuration as the default route, while eth1 (DHCP) has a specific network route. Let's examine this setup:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         RT-C0C1C0CF879F 0.0.0.0         UG    100    0        0 eth0
10.0.0.0        *               255.255.255.0   U     0      0        0 eth0
1.1.1.0         *               255.255.240.0   U     0      0        0 eth1

Method 1: Network Manager Configuration

For Ubuntu 12.04 using NetworkManager, edit the connection profile:

sudo nano /etc/NetworkManager/system-connections/Your-Eth1-Connection

Add these lines under the [ipv4] section:

[ipv4]
method=auto
never-default=false
route-metric=10

Then set eth0 to higher metric (e.g., 100):

[ipv4]
method=manual
never-default=true
address1=10.0.0.100/24,10.0.0.1
route-metric=100

Method 2: Using /etc/network/interfaces

For systems not using NetworkManager, edit:

sudo nano /etc/network/interfaces

Configure eth0 (static):

auto eth0
iface eth0 inet static
    address 10.0.0.100
    netmask 255.255.255.0
    gateway 10.0.0.1
    metric 100

Configure eth1 (DHCP) with lower metric:

auto eth1
iface eth1 inet dhcp
    metric 10

After making changes, restart networking:

sudo /etc/init.d/networking restart

Verify with:

ip route show

You should see eth1 with lower metric becoming the default route.

If you're using both interfaces for different purposes but want eth1 as default:

# Add explicit route for eth0 network
sudo ip route add 10.0.0.0/24 dev eth0 src 10.0.0.100 table main

For Ubuntu 12.04, create a post-up script:

sudo nano /etc/network/if-up.d/fixroutes

Add:

#!/bin/sh
if [ "$IFACE" = "eth1" ]; then
    ip route del default via 10.0.0.1 dev eth0
    ip route add default dev eth1
fi

Make it executable:

sudo chmod +x /etc/network/if-up.d/fixroutes

---

Here's my current routing table showing eth0 (static) as the default route:

# ip route show
default via RT-C0C0C0CF879F dev eth0 proto static metric 100 
10.0.0.0/24 dev eth0 proto kernel scope link src 10.0.0.15 
1.1.1.0/20 dev eth1 proto kernel scope link src 1.1.1.10

The default route through eth0 goes through NAT, while eth1 (DHCP) provides direct internet access. For my development environment, I need all outbound traffic to use the direct connection.

Edit /etc/network/interfaces to modify the DHCP priority:

# Configuration for eth0 (static)
auto eth0
iface eth0 inet static
    address 10.0.0.15
    netmask 255.255.255.0
    gateway 10.0.0.1
    metric 200

# Configuration for eth1 (DHCP)
auto eth1
iface eth1 inet dhcp
    metric 100

For more advanced control, create a custom routing table:

# /etc/iproute2/rt_tables
100    direct_route

# Add to /etc/network/interfaces
post-up ip route add default dev eth1 table direct_route
post-up ip rule add from 1.1.1.0/20 lookup direct_route

Check your routing table:

ip route show
ip rule show

If the route doesn't persist:
1. Check DHCP client configuration in /etc/dhcp/dhclient.conf
2. Verify NetworkManager isn't interfering (if installed)
3. Check system logs: journalctl -u networking