Troubleshooting Vagrant Public Network Connectivity Issues: Why 192.168.56.101 is Inaccessible

From your configuration, you've correctly set up a public network interface in Vagrant:

config.vm.network "public_network", ip: "192.168.56.101", :mac => "0022334455DA"

The ifconfig output shows the interface (eth1) with the correct IP address is up and running. However, there appears to be a routing issue combined with potential VirtualBox network adapter misconfiguration.

Your ip route shows two default routes:

default via 10.0.2.2 dev eth0
default via 10.0.2.2 dev eth0  metric 100
10.0.2.0/24 dev eth0  proto kernel  scope link  src 10.0.2.15
192.168.56.0/24 dev eth1  proto kernel  scope link  src 192.168.56.101

This creates ambiguity in routing decisions. The NAT interface (eth0) is taking precedence over your bridged public network (eth1).

The presence of VirtualBox Host-Only networks in your host machine's network configuration suggests potential conflicts. When using public_network with bridge mode, Host-Only adapters shouldn't interfere.

Here's how to properly configure your environment:

# Update your Vagrantfile network configuration
config.vm.network "public_network",
  ip: "192.168.56.101",
  bridge: "Intel Ethernet Connection", # Specify your exact adapter name
  auto_config: true

# Then add this provisioner to fix routing
config.vm.provision "shell", run: "always", inline: <<-SHELL
  ip route del default via 10.0.2.2 dev eth0
  ip route add default via 192.168.56.1 dev eth1
SHELL

After making these changes:

Run vagrant reload --provision
Check routes with vagrant ssh -c "ip route"
Test connectivity from host: ping 192.168.56.101

If you prefer using DHCP instead of static IP:

config.vm.network "public_network",
  use_dhcp_assigned_default_route: true,
  bridge: "Intel Ethernet Connection"

Ensure your guest VM firewall isn't blocking connections:

sudo ufw disable  # For Ubuntu
# Or
sudo systemctl stop firewalld  # For CentOS

The issue occurs when trying to access a Vagrant VM via public_network configuration. Let's examine the current setup:

# Current Vagrantfile configuration
config.vm.network "public_network", ip: "192.168.56.101", :mac => "0022334455DA"

The VM successfully obtains the IP address (192.168.56.101) on eth1 interface, as shown in ifconfig output. However, network connectivity issues persist:

# Network interface showing correct IP assignment
eth1      Link encap:Ethernet  HWaddr 00:22:33:44:55:da
          inet addr:192.168.56.101  Bcast:192.168.56.255  Mask:255.255.255.0

Several factors could be causing this connectivity issue:

VirtualBox Bridging Issues: Verify the bridge adapter is correctly bound to the host's physical NIC
```
# Check VirtualBox network settings
VBoxManage list bridgedifs
```
Firewall Restrictions: Check both host and guest firewall rules
```
# On Linux guest
sudo iptables -L -n -v
```

Routing Problems: Examine the routing table

# Current routes showing potential issues
default via 10.0.2.2 dev eth0
192.168.56.0/24 dev eth1  proto kernel  scope link  src 192.168.56.101

Here's a comprehensive approach to resolve the issue:

1. Verify VirtualBox Network Configuration

# Check VirtualBox network attachments
VBoxManage showvminfo [vmname] --details | grep "NIC"

2. Modify Vagrantfile for Better Bridging

# Improved public_network configuration
config.vm.network "public_network",
  ip: "192.168.56.101",
  bridge: "Intel Ethernet Connection", # Explicit bridge interface
  mac: "0022334455DA",
  auto_config: true

3. Network Interface Troubleshooting

# On guest VM, verify network interface settings
sudo ip link set eth1 up
sudo ip addr flush eth1
sudo dhclient -r eth1 && sudo dhclient eth1

4. Windows-Specific Fixes

For Windows hosts, these additional steps may help:

# Disable VirtualBox Host-Only adapters in Network Connections
netsh interface set interface "VirtualBox Host-Only Network" admin=disable

If automatic configuration fails, manually set up the network:

# In Vagrantfile
config.vm.provision "shell", inline: <<-SHELL
  ip addr add 192.168.56.101/24 dev eth1
  ip link set eth1 up
  ip route add default via 192.168.56.1 dev eth1 metric 100
SHELL

After applying fixes, verify connectivity:

# From host machine
ping 192.168.56.101
traceroute 192.168.56.101

# From guest VM
ping 192.168.56.1  # Should reach gateway
ping 8.8.8.8       # Test internet connectivity