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Harun Baris Bulut
Asked: 2014-06-27 12:40:04 +0800 CST

How to manage gateway assignment in different VLAN's with isc-dhcp-server?

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We are managing our network by using DHCP and we sometimes add new subnets (IP Pools) to network through different VLANs.

What we want to do is to manage all those IP pools from same DHCP server but sometimes some servers in pool has to reach multiple VLANs. In DHCP configuration we tell a pool to have a default gateway. But there occur gateway problem when a server has 2 interfaces which both has gateway option.

The sample configuration is below;

// VLAN 1 (interface 1)
subnet 10.4.0.0 netmask 255.255.0.0 {
        range 10.4.0.0 10.4.255.255;
        option broadcast-address 10.4.255.255;
}

// VLAN 2 (interface 2)
subnet 10.8.0.0 netmask 255.255.0.0 {
        range 10.8.0.0 10.8.255.255;
        option domain-name-servers 8.8.4.4,4.4.2.2;
        option routers 10.8.0.1;
        option broadcast-address 10.8.255.255;
}

// VLAN 3 (interface 3)
subnet 127.0.0.0 netmask 255.255.255.0 {
        range 127.0.0.0 127.0.0.255;
        option domain-name-servers 8.8.4.4,4.4.2.2;
        option routers 127.0.0.1;
        option broadcast-address 127.0.0.255;
}

Machine; Ubuntu 12.04 LTS 64 Bits

In this scenario we want server to select the VLAN 3 gateway (127.0.0.1 as gateway) but when VLAN 1 and VLAN 2 attached only we want server to use VLAN 2 gateway (10.8.0.1 as gateway)

When Server has
interface 1
interface 2 (10.8.0.1 should be the gateway)

When Server has 
interface 1 
interface 3 (127.0.0.1 should be the gateway)

When Server has 
interface 1 
interface 2 
interface 3 (127.0.0.1 should be the gateway)

So how can we manage this?

dhcp

0 Answers