The HTTP Content Rewrite feature allows end users to visit the HTTP contents on the Web servers behind the FortiBalancer appliance. This feature aims to reduce network latency and improve user experience.
This chapter will cover the theories and configurations of the HTTP Content Rewrite feature.
SLB (Server Load Balancing) allows you to distribute load and traffic to specific groups of servers or to a specific server. The FortiBalancer appliance supports server load balancing in Layers 2-7 of the OSI network model. Layer 2 SLB is based on network interfaces. Layer 3 SLB works on IP addresses. Layer 4 SLB is mostly concerned with port based load balancing. Layer 7 is used when you want to perform load balancing based on URLs, HTTP headers or Cookies. The basic steps for setting up SLB are:
The real server, the VIP and the virtual service are the fundamental components of SLB deployment.
The remainder of this chapter will cover these steps and cover some examples of Layer 2, Layer 3, Layer 4 and Layer 7 load balancing strategies.
This following figure is a logical overview of load balancing using the FortiBalancer appliance.
Figure 6-1 SLB Architecture
This section focuses on introducing the advanced network configurations, including VLAN, MNET, Port Forwarding, NAT, Dynamic Routing and IP Pool functionalities and configurations on the FortiBalancer appliance.
VLAN (Virtual Local Area Network) is used to logically segment a network into smaller networks by application, or function, without regard to the physical location of the users. Each VLAN is considered a separate logical network. There are two types of VLAN specifications for Ethernet network.
Define VLAN based on port number of the switch. Port-based VLAN is easy to configure but often limited to one single switch.
Tag-based VLAN allows a group of devices on different physical LAN segments to communicate with each other as if they were all on the same physical LAN segment. In tag-based VLAN, an identifying number, called a “VLAN ID” or a “tag”, is written into the Ethernet frame itself, so that switches and routers can use this information to make switching decisions. A tagged frame is four bytes longer than an untagged frame and contains two bytes of Tag Protocol Identifier (TPID) and two bytes of Tag Control Information (TCI).
The FortiBalancer appliance supports Tag-based VLAN on all interfaces. Tag-based VLAN (also known as Trunking by some vendors) is where a tag is inserted into the Ethernet frame so that switches and routers can use this information to make switching decisions.
The FortiBalancer appliance’s VLAN can work in both the IPv4 and IPv6 network environments. Administrator can view all the IPv4 and IPv6-based VLAN configurations by executing the command “show interface”.
For example:
IPv4-based VLAN:
| FortiBalancer(config)#show interface
…… V1(vlan1): flags=8843<UP,BROADCAST,RUNNING,SIMPLEX> mtu 1500 inet 10.8.66.96 netmask 0xffffff00 broadcast 10.8.66.255 ether 00:25:90:39:97:f3 media: autoselect status: no carrier vlan : 3 parent interface: port1 webwall status: OFF packet drop (not permit): 0 tcp 0 udp 0 icmp 0 ah 0 esp 0 packet drop (deny): 0 tcp 0 udp 0 icmp 0 ah 0 esp 0 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec |
IPv6-based VLAN:
FortiBalancer(config)#show interface
……
| V2(vlan2): flags=8843<UP,BROADCAST,RUNNING,SIMPLEX> mtu 1500 inet6 fe80::230:48ff:fe93:a73e prefixlen 64 scopeid 0xc ether 00:30:48:93:a7:41 media: autoselect status: no carrier
vlan : 20 parent interface: port2 webwall status: OFF packet drop (not permit): 0 tcp 0 udp 0 icmp 0 ah 0 esp 0 packet drop (deny): 0 tcp 0 udp 0 icmp 0 ah 0 esp 0 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec |
MNET (Multi-Netting) is used to assign more than one IP address on a physical interface. Here is an example for MNET:
A new Internet site is under development for a small corporation. The network administrator knows that the site will grow in the future but today there is no need for a complex network. A server is installed that will be used as Web server, FTP server, mail server, and the corporation’s DNS server. Later, when the use of the network services grows, new servers will be used for each of the functions.
When the time comes to address the current server, the administrator has a choice. A single IP address can be used on the server. Later when the new servers are needed, new IP addresses can be assigned to them.
Another way of assigning addresses can be used. The administrator can assign four IP addresses to the server. Each IP address will match the IP address to be used in the future on the new servers. The administrator now knows what addresses will be used and can create DNS entries for the new devices with the correct addresses. This process of providing more than one IP address on an interface is often called multi-netting.
The FortiBalancer appliance’s MNET can work in both the IPv4 and IPv6 network environments.
Port forwarding allows you to forward any traffic that is destined to an IP/port pair on the FortiBalancer appliance, to an IP/port pair on the inside network. External clients can directly access the internal servers via an address on the outside subnet.
Note: Port Forwarding feature cannot support FTP, users are recommended to use SLB feature instead.
For example, say that you are running SSH on a real server on the port2 interface subnet, and you want to connect to the server from a client in the outside. To get this information from the outside world to the desired inside IP/port pair, we will have to add a port forward on the FortiBalancer appliance.
Figure 2-1 Port Forwarding
NAT (Network Address Translation) is the translation of an IP address used within one network to a different IP address known within another network. One network is designated the inside network and the other is the outside. NAT is used when you want your real servers on the inside network to access the outside network. Using NAT, all packets will appear as though they came from the FortiBalancer appliance.
When a client on the inside network contacts a machine on the outside network, it sends out IP packets destined for that machine. These packets contain all the addressing information necessary to get them to their destination.
When the packets pass through the NAT gateway, they will be modified so that they appear to be coming from the NAT gateway itself. The NAT gateway will record the changes it makes in its state table so that it can reverse the changes on return packets and ensure that return packets are passed through the firewall without being blocked.
NAT Traversal of PPTP
The FortiBalancer appliance supports NAT traversal of PPTP (Point-to-Point Tunneling Protocol). PPTP is a tunneling mechanism to transfer PPP (Point-to-Point Protocol) frames across intermediate networks. PPTP uses GRE (Generic Routing Encapsulation) encapsulation for PPP payload. However, typically GRE tunnels cannot traverse the NAT device (i.e. the FortiBalancer appliance). To resolve this problem, a PPTP NAT editor is used on the FortiBalancer appliance. This editor is an additional software component on the NAT device to perform translation for IP addresses, TCP ports, and call ID.
The FortiBalancer appliance supports four types of NAT:
Mapping an IP address on one-to-one basis. By configuring static NAT, the FortiBalancer appliance maps an inside real IP address to a VIP address on the outside. For inbound traffic directed from an outside VIP, the traffic will be forwarded to a corresponding inside real IP without any change in the port number or protocol value. Thus, hosts on the inside network will be directly accessible via the VIP on the port1 interface. The outbound traffic coming from an inside host will use the corresponding outside VIP as the source IP for the outgoing traffic. The port number and protocol remain unchanged. TCP, UDP and ICMP are supported for static NAT.
In static NAT, the computer with the IP address (192.168.10.13) will be always translated into 10.10.0.3:
Figure 2-2 Static NAT
Mapping multiple inside real IP addresses to a single VIP address with a different port number assignment on the port1 interface. By configuring port-level NAT, the group of hosts on the inside network will be directly accessible via the VIP on the port1 interface.
In port-level NAT, the computers with the IP address in the range from 192.168.10.11 to 192.168.10.13 will be translated into 10.0.0.3 with a different port on the outside network:
Figure 2-3 Port-level NAT
If a port-level NAT is configured for an inside real IP address, static NAT should take precedence over the regular NAT policy. VIPs used by static NAT should not be used by regular NAT. Also, one static NAT VIP should not map to multiple real IP addresses.
Mapping one or multiple inside real IP addresses to an IP pool which contains multiple IP addresses. By configuring IP pool-based dynamic NAT, a group of hosts on the inside network will be translated into via the multiple IP addresses in IP pool.
As shown below, in IP pool-based dynamic NAT, the client IP addresses in the range from 192.168.10.11 to 192.168.10.13 will be translated into 10.0.0.1 to 10.0.0.3 and get connected to the Internet.
Figure 2-4 IP Pool-based Dynamic NAT
FortiBalancer supports NAT based on destination IP address. The destination IP based NAT can be performed only when the destination IP address is in the specified network segment and in the same network segment as the route gateway. If the gateway is set to the default value 0.0.0.0, the destination IP/IP pool for NAT and the route gateway should be within the same network segment.
Note: For IPv6 address, only TCP and UDP packets can be NATTed and no gateway can be configured.
Configuration Example via CLI
FortiBalancer(config)#ip pool “pool1” 172.16.72.45 172.16.72.55
FortiBalancer(config)#ip pool “pool3” 3ffd::45 3ffd::46
FortiBalancer(config)#nat portdst “pool1” 172.16.72.0 255.255.255.0 500 172.16.72.101
FortiBalancer(config)#nat portdst “pool3” 3ff1:: 65 50
Check NAT configurations and statistics
The following two commands can be used to check the NAT configurations and statistics. Ø Check NAT table
FortiBalancer(config)#show nat table
From 172.16.73.108(5208) through 172.16.72.53(50776) to 172.16.72.77(80)
From 172.16.73.108(5200) through 172.16.72.53(50768) to 172.16.72.77(80)
From 172.16.73.108(5880) through 172.16.72.53(51448) to 172.16.72.77(80)
From 172.16.73.108(6008) through 172.16.72.53(51576) to 172.16.72.77(80)
From 3ffd::108(42720) through 3ffd (45672) to 3ff1::77(80)
From 3ffd::108(42728) through 3ffd (45680) to 3ff1::77(80)
From 3ffd::108(43336) through 3ffd (46288) to 3ff1::77(80)
From 3ffd::108(43376) through 3ffd (46328) to 3ff1::77(80)
From 3ffd::108(43464) through 3ffd (46416) to 3ff1::77(80)
From 3ffd::108(43408) through 3ffd (46360) to 3ff1::77(80)
From 3ffd::108(43840) through 3ffd (46792) to 3ff1::77(80)
From 3ffd::108(43896) through 3ffd (46848) to 3ff1::77(80)
Ø Check NAT statistics
FortiBalancer(config)#show statistics nat
nat portdst “pool1” 172.16.72.0 255.255.255.0 500 172.16.72.101 protol(total/current):icmp(1/1) udp(0/0) tcp(23724/251) nat portdst “pool3” 3ff1:: 65 50
protol(total/current):icmp(0/0) udp(0/0) tcp(23716/246)
Dynamic Routing is a process in which routers automatically adjust to changes in network topology or traffic. It is more robust than static routing. Now, there are several protocols used to support dynamic routing including RIPv1 (Routing Information Protocol version 1), RIPv2 (Routing Information Protocol version 2) and OSPFv2 (Open Shortest Path First version 2) and OSPFv3 (Open Shortest Path First version 3).
Dynamic Routing is especially suitable for today’s large, constantly changed networks. It improves performance by allowing network routers to adjust to changes in the network topology. And it distributes routing information between routers and chooses the best path for the network, saving money and improving performance.
An IP pool contains multiple IP addresses from one IP segment. Administrators can use the pre-defined IP pools for NAT and SLB configurations.
For the NAT module, IP pool can be defined on the outside interface to realize translation of multiple outgoing IP addresses. This helps increase the concurrent capacity and fully utilize the IP resources. For the SLB module, IP pool can be defined for real server groups. Under the SLB reverse mode, when different real server groups are selected, FortiBalancer can select different IP addresses in IP pools to connect to real servers. This not only increases the concurrent connection capacity, but also provides a more flexible configuration method for administrators.
FortiBalancer appliance supports multiple IP pools, and at most 256 IP addresses can be added in one IP pool. The maximum number of IP pools allowed on the FortiBalancer appliance varies with different system memories. Please see the table below for details.
Table 2-1 Maximum IP Pool Entry
| System Memory | Maximum IP Pool Number |
| 4GB | 32 |
| 8GB | 64 |
| 16GB | 128 |
| 32GB | 256 |
Both IPv4 and IPv6 addresses can be configured in the IP pool.
When configuring the IP pool, please note:
This section will outline the initial connection, basic setup and configuration of the FortiBalancer appliance. The easy to follow setup steps are introduced below.
There are three ways to connect to the FortiBalancer appliance in order to begin the configuration:
If you choose the console connection, first connect the console cable (supplied) to the System Console Port on the FortiBalancer appliance, and then set up your console as follows:
Table 1-1 Console Setup
| Setting | Value |
| Emulation | VT 100 |
| Baud | 9600 |
| Number of Bits | 8 |
| Parity | No |
| Stop Bits | 1 |
| Flow Control | No |
Open a connection between the console and the FortiBalancer appliance. Once this connection is opened, users will see the FortiBalancer appliance prompt and may begin the configuration process.
Once the IP parameters are configured and the SSH service is activated, the FortiBalancer appliance is prepared for custom configuration. You may access the command line interface (CLI) using SSH connection. Below gives an example.
Note: If you require SSH software for Windows, Mac OS X or UNIX, it is available on-line at http://www.openssh.com.
To establish an SSH connection:
>> # ssh admin@10.3.55.251
10.3.55.251 is the FortiBalancer appliance’s IP address.
>> # ssh admin@10.3.55.251 >> # admin@10.3.55.251’s password:
Upon the first startup, the user will be prompted for login username and password. The default username is “admin”, and the default password is “admin”.
Note: You must have the IP information setup and basic network connectivity in order to access the box through SSH.
This section introduces the connection method via FortiBalancer web UI (Web User Interface). The FortiBalancer web UI can:
If administrators want to take full advantage of the Web UI access to the FortiBalancer appliance, please first assign a valid and unique IP address and a port number to the web UI. For example:
FortiBalancer(config)#webui ip 10.10.0.2
FortiBalancer(config)#webui port 8888
On the FortiBalancer appliance, we use port1’s IP address as the default web UI IP address and the port 8888 as the default web UI port.
Then, turn on the web UI function:
FortiBalancer(config)#webui on
Now open your browser of choice and connect to the FortiBalancer appliance. To do this, simply type in the address bar as such:
https://10.10.0.2:8888
And now press “Enter”. The welcome screen should appear in your browser’s window, protected by the familiar prompt asking for user name and password. The default username and password is admin and admin, just as before. If this screen does not appear, verify the address and port designations for both the port1 interface and web UI port.
The FortiBalancer appliance web UI supports the following browsers:
IE (Recommended)
Firefox
Chrome
Browser resolution should be set to 1024×786 or higher.
The FortiBalancer appliance possesses three LEDs in the front panel: one yellow, one green and one blue. The following is the usage description of each LED in the front panel.
Table 1-2 LEDs in the Front Panel
| Color | Meaning | Description |
| Yellow | Fault | This light is always off when FortiBalancer appliance keeps normal.
It means the following problems have come out if this light turns on: The CPU fan stops working. |
| Color | Meaning | Description |
| The CPU is overheated (equal to or over 85℃).
The system is overheated (equal to or over 75℃ on 1U appliances, or 85℃ on 2U appliances). One of the power supply modules breaks down (If the FortiBalancer appliance supports the dual power supply), the redundant power supply will turn on the Buzzer at the same time. |
||
| Green | Run | The green LED should blink each second when system is idle. CPU activity will be indicated by the blinking of this light; the faster the rate, the higher the CPU activity. |
| Blue | Power | Indication of power and the active state (off|on) of the FortiBalancer appliance. |
Note: If the yellow LED is lighted, please contact Customer Support. You can view system logs to get more information about the problem.
The FortiBalancer appliance provides two LEDs for every Ethernet port in the rear panel:
The following table describes the meaning of each LED on the onboard and add-on NICs of the FortiBalancer appliance.
Table 1-3 LED for Ethernet Ports in Rear Panel
| NIC Type | LED Name | Description |
| Onboard NIC | Link LED | The Link LED has the following indicator colors:
Amber: The speed mode is 1 Gbps. Green: The speed mode is 100 Mbps. Off: No Connection or the speed mode is 10 Mbps. |
| Activity
LED |
The Activity LED has the following indicator colors:
Yellow and blinking: Active Off: Inactive |
|
| Add-on NIC | Link LED | The Link LED has the Yellow indicator color, indicating 1 Gbps, 10 Mbps or 100 Mbps speed mode. |
| Activity
LED |
The Activity LED has the following indicator colors:
Green and blinking: Active Off: Inactive |
In this section, you will be provided an overview of the Command Line Interface (CLI) covering the following topics:
The CLI allows you to configure and control key functions of the FortiBalancer appliance to better manage the performance of your servers and the accessibility to the contents therein.
The FortiBalancer appliance software has been designed with specific enhancements to make interaction with the Appliance more user friendly, such as Shorthand. Shorthand is the intuitive method by which the Appliance completes CLI commands based on the first letters entered. Other user shortcuts are listed below:
Table 1-4 List of Shortcuts
| CLI Shortcuts | Operation |
| ^a/^e | Move the cursor to the beginning/end of a line. |
| ^f/^b | Move the cursor forward/backward one character. |
| Esc-f | Move the cursor forward one word. |
| Esc-b | Move the cursor backward one word. |
| ^d | Delete the character under the cursor. |
| ^k | Delete from the cursor to the end of the line. |
| ^u | Delete the entire line. |
Note: The symbol “^” indicates holding down the Control (Ctrl) Key while pressing the letter that appears after the symbol.
The FortiBalancer CLI commands will generally adhere to the following style conventions: Table 1-5 FortiBalancer CLI Style Conventions
| Style | Convention |
| Bold | The body of a CLI command is in Boldface. |
| Italic | CLI parameters are in Italic. |
| < > | Parameters in angle brackets < > are required. |
| [ ] | Parameters in square brackets [ ] are optional.
Subcommand such as “no”, “show” and “clear” commands. |
| {x|y|…} | Alternative items are grouped in braces and separated by vertical bars. At least one should be selected. |
| [x|y|…] | Optional alternative items are grouped in square brackets and separated by vertical bars. One or none is selected. |
For example:
ip address {system_ifname|mnet_ifname|vlan_ifname|bond_ifname} <ip_address> {netmask|prefix}
Note: If a string we input for configuring a parameter starts with figure, or the string contains spaces, we must put the configuration string within double quotes to make sure that we can configure the command correctly.
The FortiBalancer appliance’s Command Line Interface offers three levels of configuration and access to the OS. The CLI prompt of each level consists of the host name of the FortiBalancer appliance followed by a unique cursor prompt, either “>”, “#” or “(config)#”.
The first level is for basic network troubleshooting and is called the User level. At this level, the user is only authorized to operate some very basic commands and non-critical functions such as ping and traceroute. Here is how the User level prompt appears in the CLI.
FortiBalancer>
The second level of administration is the Enable level. Users at this level have access to a majority of view only commands such as “show version”. Users in the Enable level may execute commands from both the User and Enable levels. In order to gain access to this level of appliance management, the user must employ the command “enable”. Once this command is entered, the FortiBalancer appliance prompts the user for the appropriate password. If correct password is entered, the CLI prompt will change from “FortiBalancer>” to “FortiBalancer#”, which means the user is granted access to the Enable level. The default password for the Enable level is null, i.e. users simply need to press “Enter”.
FortiBalancer>enable Enable password:
FortiBalancer#
The final access level is the Config level. It is with this level of authority that the user can make changes to the configuration of the box. No two users can access the Config level at the same time. Once a user has gained access to this level, he or she can implement commands in all three levels. To gain access to the full configurable functions of the FortiBalancer appliance, the user must use the following command:
FortiBalancer#config terminal
Once this command is entered, the CLI prompt will change to:
FortiBalancer(config)#
In the event that Config level is not available because another Config level session has been opened, the administrator can deploy the following command to gain access to the Config level:
FortiBalancer#config terminal force
WARNING:
You are forcing other user to exit configuration mode.
In case the other user is actively changing the system configuration, the result may be unpredictable.
Do you still want to force into Configuration Mode “YES” or “NO”:
Type “YES” and press “Enter”. You will enter the Config level successfully.
For each level the user can type “?” for available commands. For example, entering
“FortiBalancer(config)#slb real ?” will prompt users with all the possible parameters or protocols the CLI will accept with the “slb real” command.
FortiBalancer(config)#slb real ? [enter]
activation Recovery and warm-up time of real service disable Remove real service from load balancing dns Define SLB DNS real service enable Activate real service for load balancing ftp Define SLB FTP real service