* [LARTC] routing with multiple uplinks problem
@ 2004-05-24 7:44 Rafal Krzewski
2004-05-24 8:36 ` Jose Luis Domingo Lopez
2004-05-24 10:38 ` Rafal Krzewski
0 siblings, 2 replies; 3+ messages in thread
From: Rafal Krzewski @ 2004-05-24 7:44 UTC (permalink / raw)
To: lartc
Hello all,
I'm writing to the list, because I have a problem setting up my routing
that I'm unable to overcome.
1. The situation:
+-------------+ +-------------+
| actaea | eth0 | ilex |
| 192.168.1.4 |------ localnet ------| 192.168.1.1 |
+-------------+ 192.168.1.0/24 +-------------+
eth1 / | ppp0
80.72.34.162 83.31.149.159
/ |
wlnet tpsa
80.72.34.160/24 |
/ |
+--------------+ +------------+
| 80.72.34.161 | | 213.25.2.3 |
+--------------+ +------------+
\ /
\-----------, /
+--------------+ "" \
| salix | / Internet "
| 212.87.7.182 |--------'-, ,-"
+--------------+ "--------"
Ilex, the router/firewall is running Debian/GNU Linux "Sarge", kernel
version 2.6.5, iproute2 tools 20010824-13, iptables 1.2.9-6
2. What I am trying to achieve:
I want ilex to respond to any incoming trafic on 80.72.34.162 address
(it is running a DNS server). All outgoing trafic from localnet should
go through tpsa link (faster but non-static IP). Resposnses to the
latter should also return through tpsa link.
I have followed instrucitons from LARTC howto, chapter 4.2 but to no avail.
3. The problem:
after running:
ip route del default
ip route add default via 213.25.2.3
localnet traffic flows fine, BUT ilex no longer responds to pings from
salix on 80.72.34.162 address
this happens also in the opposite direction, after running:
ip route del default
ip route add default via 80.72.34.161
localnet traffic flows fine, BUT ilex no longer responds to pings from
salix on 83.31.149.159 address
4. What I did to diagnose the problem:
Checked, and double checked my settings against the howto.
Tried pinging ilex from salix tracing the traffic with iptables -j LOG
(settings below). I'm able to see ping request packets, but no ping
response packets. I also tried monitoring the trafic with ethereal, both
on the virtuall 'all' interface, and also on each of the physical
interface (well, ppp0 isn't actually physical, but you get the idea) in
promiscous mode. Only ping request packets are visible.
Then I tried connecting with ssh from salix to ilex. I'm seeing incoming
SYN packets, but no response packets directed to salix emerge on either
interface.
5. Relevant diagnostic information:
ip output, with default route through wlnet link:
ilex:~# ip address show
1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:30:1b:2e:fb:c1 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.1/24 brd 192.168.1.255 scope global eth0
3: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:c0:df:f7:5c:26 brd ff:ff:ff:ff:ff:ff
inet 80.72.34.162/27 brd 80.255.255.255 scope global eth1
4: eth2: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:60:4c:17:54:7c brd ff:ff:ff:ff:ff:ff
27: ppp0: <POINTOPOINT,MULTICAST,NOARP,UP> mtu 1492 qdisc pfifo_fast qlen 3
link/ppp
inet 83.31.149.159 peer 213.25.2.3/32 scope global ppp0
ilex:~# ip rule show
0: from all lookup local
32764: from 213.25.2.3 lookup tpsa
32765: from 80.72.34.161 lookup wlnet
32766: from all lookup main
32767: from all lookup default
ilex:~# ip route show table local
local 192.168.1.1 dev eth0 proto kernel scope host src 192.168.1.1
local 83.31.149.159 dev ppp0 proto kernel scope host src 83.31.149.159
broadcast 80.72.34.160 dev eth1 proto kernel scope link src 80.72.34.162
broadcast 192.168.1.0 dev eth0 proto kernel scope link src 192.168.1.1
broadcast 127.255.255.255 dev lo proto kernel scope link src 127.0.0.1
local 80.72.34.162 dev eth1 proto kernel scope host src 80.72.34.162
broadcast 80.255.255.255 dev eth1 proto kernel scope link src
80.72.34.162
broadcast 192.168.1.255 dev eth0 proto kernel scope link src 192.168.1.1
broadcast 127.0.0.0 dev lo proto kernel scope link src 127.0.0.1
local 127.0.0.1 dev lo proto kernel scope host src 127.0.0.1
broadcast 80.72.34.191 dev eth1 proto kernel scope link src 80.72.34.162
local 127.0.0.0/8 dev lo proto kernel scope host src 127.0.0.1
ilex:~# ip route show table tpsa
213.25.2.3 dev ppp0 scope link src 83.31.149.159
80.72.34.160/27 dev eth1 scope link
192.168.1.0/24 dev eth0 scope link
127.0.0.0/8 dev lo scope link
default via 213.25.2.3 dev ppp0
ilex:~# ip route show table wlnet
213.25.2.3 dev ppp0 scope link
80.72.34.160/27 dev eth1 scope link src 80.72.34.162
192.168.1.0/24 dev eth0 scope link
127.0.0.0/8 dev lo scope link
default via 80.72.34.161 dev eth1
ilex:~# ip route show table main
213.25.2.3 dev ppp0 proto kernel scope link src 83.31.149.159
80.72.34.160/27 dev eth1 proto kernel scope link src 80.72.34.162
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.1
default via 80.72.34.161 dev eth1
ilex:~# ip route show table default
iptables output at the time of testing (disabled firewall):
ilex:~# iptables -L -n
Chain INPUT (policy ACCEPT)
target prot opt source destination
LOG all -- 83.31.149.159 0.0.0.0/0 LOG flags 0
level 4
LOG all -- 0.0.0.0/0 83.31.149.159 LOG flags 0
level 4
Chain FORWARD (policy ACCEPT)
target prot opt source destination
LOG all -- 83.31.149.159 0.0.0.0/0 LOG flags 0
level 4
LOG all -- 0.0.0.0/0 83.31.149.159 LOG flags 0
level 4
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
LOG all -- 83.31.149.159 0.0.0.0/0 LOG flags 0
level 4
LOG all -- 0.0.0.0/0 83.31.149.159 LOG flags 0
level 4
ilex:~# iptables -t nat -L -n
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
LOG all -- 83.31.149.159 0.0.0.0/0 LOG flags 0
level 4
LOG all -- 0.0.0.0/0 83.31.149.159 LOG flags 0
level 4
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
LOG all -- 83.31.149.159 0.0.0.0/0 LOG flags 0
level 4
LOG all -- 0.0.0.0/0 83.31.149.159 LOG flags 0
level 4
MASQUERADE all -- 192.168.0.0/16 0.0.0.0/0
MASQUERADE all -- 192.168.0.0/16 0.0.0.0/0
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
LOG all -- 83.31.149.159 0.0.0.0/0 LOG flags 0
level 4
LOG all -- 0.0.0.0/0 83.31.149.159 LOG flags 0
level 4
Note: the seemingly indentical MASQUERADE entries in the POSTROUTING
chain are:
-s 192.168.0.0/16 -o eth1 -j MASQUERADE
-s 192.168.0.0/16 -o ppp0 -j MASQUERADE
My apologies for a rather lenghty email. I'm trying to provide all
information that I have in order to reduce mailing list noise.Please
help - I am stuck.
Thanks in advance,
Rafal
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [LARTC] routing with multiple uplinks problem
2004-05-24 7:44 [LARTC] routing with multiple uplinks problem Rafal Krzewski
@ 2004-05-24 8:36 ` Jose Luis Domingo Lopez
2004-05-24 10:38 ` Rafal Krzewski
1 sibling, 0 replies; 3+ messages in thread
From: Jose Luis Domingo Lopez @ 2004-05-24 8:36 UTC (permalink / raw)
To: lartc
On Monday, 24 May 2004, at 09:44:43 +0200,
Rafal Krzewski wrote:
> +-------------+ +-------------+
> | actaea | eth0 | ilex |
> | 192.168.1.4 |------ localnet ------| 192.168.1.1 |
> +-------------+ 192.168.1.0/24 +-------------+
> eth1 / | ppp0
> 80.72.34.162 83.31.149.159
>
> / |
> wlnet tpsa
> 80.72.34.160/24 |
> / |
> +--------------+ +------------+
> | 80.72.34.161 | | 213.25.2.3 |
> +--------------+ +------------+
> \ /
> \-----------, /
> +--------------+ "" \
> | salix | / Internet "
> | 212.87.7.182 |--------'-, ,-"
> +--------------+ "--------"
>
> I want ilex to respond to any incoming trafic on 80.72.34.162 address
> (it is running a DNS server). All outgoing trafic from localnet should
> go through tpsa link (faster but non-static IP). Resposnses to the
> latter should also return through tpsa link.
>
For the localnet traffic to exit your premises through tpsa you must
route this traffic through 213.25.2.3 as next hop with outgoing device
ppp0. You _must_ SNAT this traffic to 83.31.149.159, this way return
traffic will always come back from the Internet trhrough this same link.
> after running:
> ip route del default
> ip route add default via 213.25.2.3
> localnet traffic flows fine, BUT ilex no longer responds to pings from
> salix on 80.72.34.162 address
>
The problem seems clear to me: your routing table at ilex will only have
entries for the directly connected networks and the default route you
have just show. So every traffic coming from a network different from
the local connected ones will get routed through the default gateway.
Maybe traffic arrives at its destination, but in its way back gets
routed along a different path (asymmetric routing) and is dropped or
lost somewhere.
> 4. What I did to diagnose the problem:
> Tried pinging ilex from salix tracing the traffic with iptables -j LOG
> (settings below). I'm able to see ping request packets, but no ping
> response packets. I also tried monitoring the trafic with ethereal, both
> on the virtuall 'all' interface, and also on each of the physical
> interface (well, ppp0 isn't actually physical, but you get the idea) in
> promiscous mode. Only ping request packets are visible.
>
I think tcpdump or ethereal is the way to go. Try to detect the traffic
from its source to its destination, and at each point see if packets are
as expected with respect to IP addresses. It seems traffic arrives OK at
ilex but this box doesn't reply to this traffic, whether this is ICMP or
even TCP connections (ssh).
Put a tcpdump/ethereal on the incoming interface, note down IP addresses
and ports (if applicable), and then have a look at:
http://www.docum.org/stef.coene/qos/kptd/
Try to depict the path the traffic would theoretically follow inside the
kernel paying attention both to iptables rules as well as the routing
policy database (both "ip rules" and "ip routes"). Traffic should end
up being received by the "kernel", and a reply should come back. Even if
it is not the case the kernel should log something, check with "dmesg".
> ilex:~# ip rule show
> 0: from all lookup local
> 32764: from 213.25.2.3 lookup tpsa
> 32765: from 80.72.34.161 lookup wlnet
> 32766: from all lookup main
> 32767: from all lookup default
>
"ip rules" 32764 and 32765 will only apply to traffic with source IP
addresses as shown, but not to traffic coming through any of the
associated routers (except this routers also do SNAT to traffic coming
from the Internet). So packets from salix (212.87.7.182) will be routed
looking first at table local (the one that should apply to traffic
ending at ilex itself), and then loooking at "table main".
The good thing about "table local" is that should be ok with no
administrator intervention, so the problem must be somewhere.
I apologize for not reading and checking the whole email to see if I
find the problem, but I am convinced this is a simple problem with
routing. The strange thing is traffic arriving at ilex, but this box no
replying back to the source.
Hope it helps.
--
Jose Luis Domingo Lopez
Linux Registered User #189436 Debian Linux Sid (Linux 2.6.6)
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [LARTC] routing with multiple uplinks problem
2004-05-24 7:44 [LARTC] routing with multiple uplinks problem Rafal Krzewski
2004-05-24 8:36 ` Jose Luis Domingo Lopez
@ 2004-05-24 10:38 ` Rafal Krzewski
1 sibling, 0 replies; 3+ messages in thread
From: Rafal Krzewski @ 2004-05-24 10:38 UTC (permalink / raw)
To: lartc
Jose Luis Domingo Lopez wrote:
>>+-------------+ +-------------+
>>| actaea | eth0 | ilex |
>>| 192.168.1.4 |------ localnet ------| 192.168.1.1 |
>>+-------------+ 192.168.1.0/24 +-------------+
>> eth1 / | ppp0
>> 80.72.34.162 83.31.149.159
>>
>> / |
>> wlnet tpsa
>> 80.72.34.160/24 |
>> / |
>> +--------------+ +------------+
>> | 80.72.34.161 | | 213.25.2.3 |
>> +--------------+ +------------+
>> \ /
>> \-----------, /
>> +--------------+ "" \
>> | salix | / Internet "
>> | 212.87.7.182 |--------'-, ,-"
>> +--------------+ "--------"
>>ilex:~# ip rule show
>>0: from all lookup local
>>32764: from 213.25.2.3 lookup tpsa
>>32765: from 80.72.34.161 lookup wlnet
>>32766: from all lookup main
>>32767: from all lookup default
>>
>
> "ip rules" 32764 and 32765 will only apply to traffic with source IP
> addresses as shown, but not to traffic coming through any of the
> associated routers (except this routers also do SNAT to traffic coming
> from the Internet). So packets from salix (212.87.7.182) will be routed
> looking first at table local (the one that should apply to traffic
> ending at ilex itself), and then loooking at "table main".
And... this was the problem!
I misread the following lines from the HOWTO:
ip rule add from $IP1 table T1
ip rule add from $IP2 table T2
as:
ip rule add from $P1 table T1
ip rule add from $P2 table T2
resulting in invalid rule entries
Now, with the following rule table everything works correctly:
ilex:~# ip rule show
0: from all lookup local
32764: from 83.31.149.159 lookup tpsa
32765: from 80.72.34.162 lookup wlnet
32766: from all lookup main
32767: from all lookup default
Many thanks for pointing me the right direction!
Rafal
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
^ permalink raw reply [flat|nested] 3+ messages in thread
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2004-05-24 7:44 [LARTC] routing with multiple uplinks problem Rafal Krzewski
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2004-05-24 10:38 ` Rafal Krzewski
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