[LARTC] Multipath Routing in same subnet - Please take a look

[LARTC] Multipath Routing in same subnet - Please take a look

[Christian Schmid]

Hello.

I have the problem that I have two gateways on the same subnet, 80.237.244.1 and 80.237.244.33. Both 
gateways are 100 MBit cards, so I have 2 times 100 MBit to the Internet. The NIC in the server is a 
gigabit-card, so this card is easy able to use both gateways for outgoing traffic.

Now I just want to use both gateways for my outgoing traffic but no matter what I do, it doesnt 
work. I tried "ip route replace default scope global nexthop via 80.237.244.1 dev eth1 weight 100 
nexthop via 80.237.244.33 dev eth1 weight 100" but it only either sends all traffic to .1 or all to 
.33. I have many downloaders so it shouldnt be a problem, should it? Its a 2.6.12rc3 kernel with 
advanced router enabled and all multipath-options enabled as well. "ip" doesnt give an error and "ip 
route ls" shows the following:

80.237.244.0/26 dev eth1  proto kernel  scope link  src 80.237.244.52
default
         nexthop via 80.237.244.1  dev eth1 weight 100
         nexthop via 80.237.244.33  dev eth1 weight 100


I have read postings on the net but all of them are using huge scripts because they are on different 
networks. My problem seems to be a much easier problem but I just cant get this to work..... :(

Please help.

Best regards,
Chris
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Re: [LARTC] Multipath Routing in same subnet - Please take a look

[gypsy]

Christian Schmid wrote:
> 
> Hello.

> 80.237.244.0/26 dev eth1  proto kernel  scope link  src 80.237.244.52
> default
>          nexthop via 80.237.244.1  dev eth1 weight 100
>          nexthop via 80.237.244.33  dev eth1 weight 100

Do not use weight parameters exceeding a single digit!
 
> I have read postings on the net but all of them are using huge scripts because they are on different
> networks. My problem seems to be a much easier problem but I just cant get this to work..... :(
> 
> Please help.
> 
> Best regards,
> Chris

I'm no expert, but my suggestion is to use 2 NICs and connect one to
each uplink or at least add 2 entries into /etc/iproute2/rt_tables.  I
think you'll find a similar situation answered in the ML within the last
10 days or so, but I can't recall the subject of the thread.  Nor can I
find anything specifying exactly what rt_tables needs to contain :/

You can review what I've gleaned from this ML at 
http://yesican.chsoft.biz/lartc

The most urgent things for you to know:
1) The LARTC HOWTO is wrong
2) You must apply Julian's patch
3) You _really_ need to read nano.txt
4) All of the intelligible success stories WRT multipath are either on
yesican or are linked to from there.

--gypsy
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Re: [LARTC] Multipath Routing in same subnet - Please take a look

[Alexander Samad]

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On Fri, May 06, 2005 at 08:41:55PM -0700, gypsy wrote:
> Christian Schmid wrote:
> > 
> > Hello.
> 
> > 80.237.244.0/26 dev eth1  proto kernel  scope link  src 80.237.244.52
> > default
> >          nexthop via 80.237.244.1  dev eth1 weight 100
> >          nexthop via 80.237.244.33  dev eth1 weight 100
> 
> Do not use weight parameters exceeding a single digit!
>  
> > I have read postings on the net but all of them are using huge scripts because they are on different
> > networks. My problem seems to be a much easier problem but I just cant get this to work..... :(
> > 
> > Please help.
> > 
> > Best regards,
> > Chris
> 
> I'm no expert, but my suggestion is to use 2 NICs and connect one to
> each uplink or at least add 2 entries into /etc/iproute2/rt_tables.  I
> think you'll find a similar situation answered in the ML within the last
> 10 days or so, but I can't recall the subject of the thread.  Nor can I
> find anything specifying exactly what rt_tables needs to contain :/
> 
> You can review what I've gleaned from this ML at 
> http://yesican.chsoft.biz/lartc
> 
> The most urgent things for you to know:
> 1) The LARTC HOWTO is wrong
> 2) You must apply Julian's patch
> 3) You _really_ need to read nano.txt
> 4) All of the intelligible success stories WRT multipath are either on
> yesican or are linked to from there.

here is my setup (firewall with 2 default routes) eth0 = cable,  ppp0
adsl.  I changed the dhcpd client to add the default route for each in
on a different metric, that way if the one of the lines is out the other
default route will still work!



from ip r (whith some stuff removed - but the essential stuff is here)

default  metric 5 
        nexthop via 141.168.16.1  dev eth0 weight 4
        nexthop via 202.7.162.89  dev ppp0 weight 2
default via 141.168.16.1 dev eth0  metric 10 
default via 202.7.162.89 dev ppp0  metric 20 


from ip ru
0:      from all lookup local 
200:    from 141.168.16.16 lookup cable 
201:    from 60.240.81.237 lookup adsl 
32766:  from all lookup main 
32767:  from all lookup default 


the important ones are 200, 201 these setup up the routing for each of
the different legs - cause they will be different! so 141.168.16.16 is
on eth0 and 60.240.81.237 is on ppp0 (they are the actual address on
the interfaces)

cat /etc/iproute2/rt_tables (these are where the names come from above!)
#
# reserved values
#
255     local
254     main
253     default
0       unspec
#
# local
#
#1      inr.ruhep

200 cable
201 adsl


These are the routing tables for 200 and 201, the 192.168 address are
the local address. The routing engine workes from the lowest numbered ru
(from ip ru ) and works to the larger numbered ones until it finds a
rule that matches!

# ip r sh tab 200
192.168.11.0/24 dev br0  scope link 
192.168.10.0/24 dev eth3  scope link 
192.168.9.0/24 dev eth4  scope link 
default via 141.168.16.1 dev eth0 
default via 141.168.16.1 dev eth0  metric 10 

# ip r sh tab 201
192.168.11.0/24 dev br0  scope link 
192.168.10.0/24 dev eth3  scope link 
192.168.9.0/24 dev eth4  scope link 
default via 202.7.162.89 dev ppp0 


Hope that helps


> 
> --gypsy
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Re: [LARTC] Multipath Routing in same subnet - Please take a look

[Andy Furniss]

Christian Schmid wrote:

>         nexthop via 80.237.244.1  dev eth1 weight 100
>         nexthop via 80.237.244.33  dev eth1 weight 100
> 
> 
> I have read postings on the net but all of them are using huge scripts 
> because they are on different networks. My problem seems to be a much 
> easier problem but I just cant get this to work..... :(

Saw this on netdev, solution disable IP_ROUTE_MULTIPATH_CACHED

http://news.gmane.org/find-root.php?group=gmane.linux.network&article%774

Andy.
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