Load Balancing - Single Multipath Route
HOWTO
Shakthi Kannan, shaks_wants_no_spam_at_shakthimaan_dot_com
January 5, 2007
Abstract
1 Network Diagram
-| R o u t e r -| -| 1 9 2 . 1 6 8 . 2 0 1 . 1 | ( et h 0 ) -| S w i t c h -| -| | 1 9 2 . 1 6 8 . 2 0 1 . 1 1 | | 1 9 2 . 1 6 8 . 2 0 1 . 1 3 ( e t h 1 ) - - - ( e t h 2 ) | PC2 | -1 9 2 . -1 6 8 . 0 . -1 | ( e t h 0 ) | | | 1 9 2 . 1 6 8 . 0 . 4 | ( e t h 0 ) -| PC1 |-1.1 Install the kernel sources
Redhat 9.0 is used for testing, and the kernel sources are not installed by default. Redhat
9.0 uses the 2.4.20-8 kernel. You can get the:
kernel - source - 2 . 4 . 2 0 - 8 . i 3 86 . rpm
from the 2nd installation CD and install it using:
rpm - ivh kernel - source - 2 . 4 . 2 0 - 8 . i 3 8 6 . rpm
The kernel sources will get installed in /usr/src/linux-2.4.20-8.
1.2 Build iptables
The iptables version present in Redhat 9.0 does not have the –to-source option for SNAT.
Hence, you need to download iptables v1.2.11. Extract the same and run the following
in its sources directory:
m a k e K E R N E L _ D I R =/ usr / src / linux - 2 . 4 . 2 0 - 8
m a k e i n s t a l l K E R N E L _ D I R =/ usr / src / linux - 2 . 4 . 2 0 - 8
1.3 Run patch-o-matic
patch-o-matic-ng does not work with 2.4.20 Linux kernels. Hence, you need to download
patch-o-matic-20031219.tar.bz2. Extract the same and do:
K E R N E L _ D I R =/ usr / src / linux - 2 . 4 . 2 0 - 8 \
I P T A B L E S _ D I R =/ p a t h / to / i p t a b l e s / s o u r c e s ./ r u n m e b a s e
It will prompt for applying various patches. Say N to all, except for the random.patch.
1.4 Recompile the kernel
The 2.4.20-8custom kernel will be built when you recompile the kernel.
m a k e c l e a n m a k e dep m a k e b z I m a g e m a k e m o d u l e s m a k e m o d u l e s _ i n s t a l l cp ar c h / i 3 86 / b o o t / b z I m a g e / b o o t / vmlinuz - 2 . 4 . 2 0 - 8 c u s t o m m k i n i t r d / b o o t / initrd - 2 . 4 . 2 0 - 8 c u s t o m . img 2. 4 . 2 0 - 8 c u s t o m
1.5 Update grub
Update the grub boot-loader, /boot/grub/menu.lst file:
t i t l e R e d h a t GNU / L i n u x ( 2 . 4 . 2 0 - 8 c u s t o m ) r o o t ( hd0 ,0)
k e r n e l / vmlinuz - 2 . 4 . 2 0 - 8 c u s t o m ro r o o t = L A B E L =/ i n i t r d / initrd - 2 . 4 . 2 0 - 8 c u s t o m . img
Reboot into the new kernel.
1.7 Load the driver modules
Check if the network driver modules are loaded, else load them using modprobe or
insmod. Load the ip_tables.o and ipt_random.o drivers.
1.8 iptables script
Create the loadbalance.sh script.
$ I P T A B L E S - t m a n g l e - A E T H 2 - p tcp - j LOG - - log - p r e f i x \ " M A N G L E _ T C P _ E T H 2 " $ I P T A B L E S - t m a n g l e - A E T H 2 - p i c mp - j LOG - - log - p r e f i x \ " M A N G L E _ I C M P _ E T H 2 " $ I P T A B L E S - t m a n g l e - A E T H 2 - j M A RK - - set - m a r k 2 $ I P T A B L E S - t nat - N S P O O F _ E T H 1 $ I P T A B L E S - t nat - F S P O O F _ E T H 1
$ I P T A B L E S - t nat - A S P O O F _ E T H 1 - j LOG - - log - p r e f i x \ " S P O O F _ E T H 1 "
$ I P T A B L E S - t nat - A S P O O F _ E T H 1 - j S N A T - - to - s o u r c e \ 1 9 2 . 1 6 8 . 2 0 1 . 1 1
$ I P T A B L E S - t nat - N S P O O F _ E T H 2 $ I P T A B L E S - t nat - F S P O O F _ E T H 2
$ I P T A B L E S - t nat - A S P O O F _ E T H 2 - j LOG - - log - p r e f i x \ " S P O O F _ E T H 2 " $ I P T A B L E S - t nat - A S P O O F _ E T H 2 - j S N A T - - to - s o u r c e \ 1 9 2 . 1 6 8 . 2 0 1 . 1 3 e c h o " S e t t i n g s o me l o c a l n e t w o r k r u l e s . . . " $ I P T A B L E S - A I N P U T - p i c m p - s 1 9 2 . 1 6 8 . 0 . 0 / 2 4 - d 1 9 2 . 1 6 8 . 0 . 1 \ - j A C C E P T e c h o " S e t t i n g M a n g l e r u l e s for e t h 1 . . ." $ I P T A B L E S - t m a n g l e - A O U T P U T - o ! e t h 0 - m r a n d o m - - a v e r a g e 50 \ - j ET H 1 $ I P T A B L E S - t m a n g l e - A P R E R O U T I N G - i e t h 0 - m r a n d o m - - a v e r a g e 50 \ - j ET H 1
ip ro add t a b l e 10 d e f a u l t via 1 9 2 . 1 6 8 . 2 0 1 . 1 dev e th 1 ip ru add f w m a r k 1 t a b l e 10 ip ro fl ca e c h o " S e t t i n g M a n g l e r u l e s for e t h 2 . . ." $ I P T A B L E S - t m a n g l e - A O U T P U T - o ! e t h 0 - m r a n d o m - - a v e r a g e 50 \ - j ET H 2 $ I P T A B L E S - t m a n g l e - A P R E R O U T I N G - i e t h 0 - m r a n d o m - - a v e r a g e 50 \ - j ET H 2
ip ro fl ca
e c h o " S e t t i n g up s p o o f i n g r u l e s . . . "
$ I P T A B L E S - t nat - A P O S T R O U T I N G - o e t h 1 - j S P O O F _ E T H 1 $ I P T A B L E S - t nat - A P O S T R O U T I N G - o e t h 2 - j S P O O F _ E T H 2
e c h o " A d d i n g d e f a u l t r o u t e . . . "
ip ro add d e f a u l t n e x t h o p via 1 9 2 . 1 6 8 . 2 0 1 . 1 dev e t h1 w e i g h t 1 \ n e x t h o p via 1 9 2 . 1 6 8 . 2 0 1 . 1 dev e th 2 w e i g h t 1 e c h o " D i s a b l i n g R e v e r s e P a t h F i l t e r i n g . . . " e c h o 0 > / p ro c / sys / net / i pv 4 / c o n f / e t h 1 / r p _ f i l t e r e c h o 0 > / p ro c / sys / net / i pv 4 / c o n f / e t h 2 / r p _ f i l t e r e c h o " E n a b l i n g I Pv 4 P a c k e t f o r w a r d i n g .. . " e c h o "1" > / p r o c / sys / net / i p v 4 / i p _ f o r w a r d
Run it.
sh l o a d b a l a n c e . sh1.9 Testing
Add a default route for PC2 from PC1:
r o u t e add d e f a u l t gw 1 9 2 . 1 6 8 . 0 . 1 et h 0
Ping the gateway IP address from PC1:
p i n g 1 9 2 . 1 6 8 . 2 0 1 . 1
