[LARTC] multipath routing question

[LARTC] multipath routing question

[Joshua Szmajda]

Hi All,

I have a linux router, configured with two internet connections and two 
lan segments. I've setup multipath routing as described in 
http://lartc.org/howto/lartc.rpdb.multiple-links.html

My problem (I think) is that somehow the router will randomly choose
incorrect routing paths for different hosts, for example:
on my workstation (192.168.1.20), I ssh to a server I have on an
external network (157.238.135.60), and my connection locally hangs. On
the router, I search the routing cache:

# ip route show cache | grep 157.238.135.60
157.238.135.60 via 207.180.31.137 dev eth0  src 207.180.31.140
157.238.135.60 from 192.168.1.20 tos 0x10 via 10.14.1.1 dev ppp0  src
192.168.1.1
157.238.135.60 from 192.168.1.20 via 207.180.31.137 dev eth0  src
192.168.1.1
192.168.1.20 from 157.238.135.60 dev eth3  src 207.180.31.140

Compare this to cache entries for a host that does work (157.238.135.90):
# ip route show cache | grep 157.238.135.90
192.168.1.20 from 157.238.135.90 tos 0x10 dev eth3  src 207.180.31.140
157.238.135.90 via 10.14.1.1 dev ppp0  src 151.203.160.233
192.168.1.20 from 157.238.135.90 dev eth3  src 207.180.31.140
157.238.135.90 from 192.168.1.20 via 10.14.1.1 dev ppp0  src 192.168.1.1
157.238.135.90 from 192.168.1.20 tos 0x10 via 10.14.1.1 dev ppp0  src
192.168.1.1

My question is: why does this happen? what can I do to fix it?

Thanks in advance!

Here's some information from my router:

# ip route
10.14.1.1 dev ppp0  scope link  src 151.203.160.233
207.180.31.136/29 dev eth0  scope link  src 207.180.31.140
192.168.1.0/24 dev eth3  scope link  src 192.168.1.1
10.0.0.0/16 dev eth2  scope link  src 10.0.0.1
127.0.0.0/8 dev lo  scope link
default
        nexthop via 207.180.31.137  dev eth0 weight 2
        nexthop via 10.14.1.1  dev ppp0 weight 1

# ip rule show
0:      from all lookup local
32764:  from 151.203.160.233 lookup T2
32765:  from 207.180.31.140 lookup T1
32766:  from all lookup main
32767:  from all lookup 253

# ip route show table T1
207.180.31.136/29 dev eth0  scope link  src 207.180.31.140
192.168.1.0/24 dev eth3  scope link  src 192.168.1.1
10.0.0.0/16 dev eth2  scope link  src 10.0.0.1
127.0.0.0/8 dev lo  scope link
default via 207.180.31.137 dev eth0  src 207.180.31.140

# ip route show table T2
10.14.1.1 dev ppp0  scope link  src 151.203.160.233
192.168.1.0/24 dev eth3  scope link  src 192.168.1.1
10.0.0.0/16 dev eth2  scope link  src 10.0.0.1
127.0.0.0/8 dev lo  scope link
default via 10.14.1.1 dev ppp0  src 151.203.160.233

Thanks Again,

-Josh

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[LARTC] multipath routing question

[Thiago Vinhas]

Hi,

I was reading some old posts on this list, and found this post 
(http://mailman.ds9a.nl/pipermail/lartc/2005q1/014963.html) with a link for a 
ip route script that is basically what I need.

My question is: when adding ip route rules, should I remove the traditional 
default gateway of my linux router?

Regards,
Thiago Vinhas
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