PC Router between wireless and Ethernet interface

[BoonPing]

Hi,

I tried to setup a connection as below but face some problem (probably route table setting incorrect). Hope if anyone could shed the light...

Basically, I have a PC1 (.1) and PC2 (.130) connected via a PC router. PC router has 2 interfaces: wireless (.2) and ethernet (.129). PC1 connects to PC router via LAN cable/wireless interface, while PC2 connects to PC router via cable. This settings try to simulate 1 wireless connection along the path (and because PC2 is too old to support wireless interface, we need a PC router). These interfaces are all under same 172.16.130.x subnet.

[PC1](.1)--ethernet--[wireless AP]--wireless--(.2)[PC router](.129)--ethernet--[dummy switch]--ethernet-- (.130)[PC2]


I tried to check the settings at PC router by PING.
The problem is

(a)PING success from .1 to .129,

(b)PING fail from .129 to .1.

(c)PING success from .130 to .2

(d)PING fail from .2 to .130.

(e)PING fail from .1 to .130 (ICMP request from .1 reach .2 but does not forward to .129)

(f)PING fail from .130 to .1 (ICMP request from .130 reach .129 but does not forward to .2)

(g)PING success between adjacent interface (eg. .1 to .2 and vice versa, .129 to .130 and vice versa).

(h)PING fail between .129<>.2 using non loopback fail (expected since no conn btw 2 interface).


My question is why PING A -> B success, but PING B->A fail??


--------------------------------------------
Below are the settings of Ubuntu 9.04 at PC Router
--------------------------------------------

root@atdg-desktop:~# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
172.16.130.128 0.0.0.0 255.255.255.128 U 1 0 0 eth0
172.16.130.0 0.0.0.0 255.255.255.0 U 2 0 0 ra0
169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0
0.0.0.0 172.16.130.2 0.0.0.0 UG 0 0 0 ra0
0.0.0.0 172.16.130.129 0.0.0.0 UG 0 0 0 eth0

-----------------------

root@atdg-desktop:~# sysctl -a | grep forward
error: "Invalid argument" reading key "fs.binfmt_misc.register"
error: permission denied on key 'net.ipv4.route.flush'
net.ipv4.conf.all.forwarding = 1
net.ipv4.conf.all.mc_forwarding = 0
net.ipv4.conf.default.forwarding = 1
net.ipv4.conf.default.mc_forwarding = 0
net.ipv4.conf.lo.forwarding = 1
net.ipv4.conf.lo.mc_forwarding = 0
net.ipv4.conf.eth0.forwarding = 1
net.ipv4.conf.eth0.mc_forwarding = 0
net.ipv4.conf.eth1.forwarding = 1
net.ipv4.conf.eth1.mc_forwarding = 0
net.ipv4.conf.ra0.forwarding = 1
net.ipv4.conf.ra0.mc_forwarding = 0
net.ipv4.conf.pan0.forwarding = 1
net.ipv4.conf.pan0.mc_forwarding = 0
net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 0
net.ipv6.conf.default.forwarding = 0
net.ipv6.conf.lo.forwarding = 0
error: permission denied on key 'net.ipv6.route.flush'
net.ipv6.conf.eth0.forwarding = 0
net.ipv6.conf.eth1.forwarding = 0
net.ipv6.conf.ra0.forwarding = 0
net.ipv6.conf.pan0.forwarding = 0

----------------------------------

root@atdg-desktop:~# cat /proc/sys/net/ipv4/ip_forward
1

----------------------------------

root@atdg-desktop:~# iptables --list
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination


----------------------------------

root@atdg-desktop:~# arp -n
Address HWtype HWaddress Flags Mask Iface
172.16.130.130 ether [CorrectMAC] CM ra0
172.16.130.130 ether [CorrectMAC] C eth0
172.16.130.1 ether [CorrectMAC] CM ra0
172.16.130.1 ether [CorrectMAC] C eth0

[BkkBonanza]

I didn't figure out all your routing and details there but it looks to me like you have overlapping networks.

172.16.130.0/24
172.16.130.128/25

Which likely gives you different routes depending on direction.
Also you have two default gateways set. Not sure how that plays out but if it round-robins on them then perhaps one path isn't correct. Pinging multiple times with different results could indicate that.

Using traceroute instead of ping could show you more.

[BoonPing]

172.16.130.0/24
172.16.130.128/25

Which likely gives you different routes depending on direction.

Ya. You're right.
I have set net.ipv4.conf.all.forwarding = 1 in PC Router and hoping both ra0 and eth0 interface would forward packets between each other.



Also you have two default gateways set.
This is the part that I'm not quite sure it's correct or even if it's effective?!

I tried traceroute but it does not give in-sight of how packet is routed in PC router since traceroute assumed it's single hop.

To make the question simple.......
Why trigger the below command in PC router fail?
> ping 172.16.130.130 -I ra0

:cry:. Ain't PC router should route/forward it such as .2 -> .129 -> .130 for echo request, then .130 -> .129 -> .2 for echo reply?

[BoonPing]

Hmm... I resolved this problem by
a) changing 2 interfaces for PC router into different subnet. Wireless subnet 130.x, and Ethernet subnet 140.x

[PC1](.130.1)--ethernet--[wireless AP]--wireless--(.130.2)[PC router](140.1)--ethernet--[dummy switch]--ethernet-- (140.2)[PC2]

b) at PC1 , because vlan is enabled here, I have added route towards 140.x

sudo route add –net 172.16.140.0 dev vlan130 netmask 255.255.255.0


Just making note for future reader. I guess PC forwarder does not work for same subnet, question remain unanswered...