[LARTC] Strange routing limitations and workaroud

[Szymon Miotk]

Hi!

I got some strange problem with routing loadbalancing.
I cannot get the full speed from my ISPs until I get some big files from close ftp server.
I have server with one connection to internal network and 3 to ISPs:


__________
| eth1|---- ISP1
| |
internal--|eth0 eth2|---- ISP2
net | |
(~300 | eth3|---- ISP3
hosts |_________|

I have done everything as described in LARTC, chapter 4.2

The main rule looks like that (the weight reflects link speed/100):
ip route add default scope global \
nexthop via $ISP1_GATEWAY dev eth1 weight 12 \
nexthop via $ISP2_GATEWAY dev eth2 weight 10 \
nexthop via $ISP3_SPRINT_GATEWAY dev eth3 weight 20

Total bandwidth available is 4.2 Mbit.
After I restart the server I can get 2.0Mbit maximum, with first link 5% utilized, and the second link and the third about 50%.
When I get some big files from close ftp server (4 x linux kernel = ~80MB) the links start to work normal, reaching 75-100% utilization. All those big files go via the first link.

Can someone possibly explain that and teach me how to get full speed without such shamanism?

Szymon Miotk

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