Installation guide

effectively cluster FTP, you must configure the LVS routers to handle both active

and passive connections.

The FTP client/server relationship can potentially open a large number of ports

that the Piranha Configuration Tool and IPVS do not know about.

5.2. How This Affects LVS Routing

IPVS packet forwarding only allows connections in and out of the cluster based on it recognizing

its port number or its firewall mark. If a client from outside the cluster attempts to open a port

IPVS is not configured to handle, it drops the connection. Similarly, if the real server attempts to

open a connection back out to the Internet on a port IPVS does not know about, it drops the

connection. This means all connections from FTP clients on the Internet must have the same

firewall mark assigned to them and all connections from the FTP server must be properly

forwarded to the Internet using network packet filtering rules.

5.3. Creating Network Packet Filter Rules

Before assigning any iptables rules for FTP service, review the information in Section 4.1,

“Assigning Firewall Marks” concerning multi-port services and techniques for checking the

existing network packet filtering rules.

Below are rules which assign the same firewall mark, 21, to FTP traffic. For these rules to work

properly, you must also use the VIRTUAL SERVER subsection of Piranha Configuration Tool

to configure a virtual server for port 21 with a value of 21 in the Firewall Mark field. See

Section 6.1, “The VIRTUAL SERVER Subsection” for details.

5.3.1. Rules for Active Connections

The rules for active connections tell the kernel to accept and forward connections coming to the

internal floating IP address on port 20 — the FTP data port.

The following iptables command allows the LVS router to accept outgoing connections from

the real servers that IPVS does not know about:

/sbin/iptables -t nat -A POSTROUTING -p tcp -s n.n.n.0/24 --sport 20 -j

MASQUERADE

In the iptables command, n.n.n should be replaced with the first three values for the floating

IP for the NAT interface's internal network interface defined in the GLOBAL SETTINGS panel of

Piranha Configuration Tool.

5.3.2. Rules for Passive Connections

The rules for passive connections assign the appropriate firewall mark to connections coming in

from the Internet to the floating IP for the service on a wide range of ports — 10,000 to 20,000.

How This Affects LVS Routing