arp problem in pinging host

Hello,
I have pc hostA with 192.168.1.100 connected to pc R1 with
eth0:10.1.1.1 and eth1:192.168.1.1 via crosscable when i ping from
hosta to R1 request packet goes to R1 but R1 generates packets with
srcip=0.0.0.0 and destination ip of R1's eth1=192.168.1.1 and hosta
unable to receive reply packet from R1. But if i ping from R1 to hosta
packet always goes to hosta and receives reply at R1. What can be the
reason is that arp cache problem or what else?
When i send ping packet to R1 from hostA, the arp analysis on my
both Linux machines shows that when i did arp -a on hosta and found
output that
R1(192.168.1.1) at <incomplete> on eth0
and on R1 nothing is displayed.
When i send ping packet to hostA from R1, the arp analysis on
my both Linux machines shows that when i did arp -a on R1 and found
output that

Address HWtype HWaddress Flags Mask
Iface
hosta ether 00:08:F1:43:62:91 C
eth1

and on hosta
Address HWtype HWaddress Flags Mask
Iface
R1 ether 00:08:F1:43:61:C1 C
eth0

whats wrong in hosta linux machine?



cranium.2003@gmail.com

Post the routing tables. Are you sure the crossover cable is between
the right NICs?

Routing table for hostA
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
eth0
172.16.1.0 192.168.1.1 255.255.255.0 UG 0 0 0
eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0
eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
lo
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0
eth0

Routing table for R1
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
eth1
172.16.1.0 0.0.0.0 255.255.255.0 UG 0 0 0 eth0
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
lo
0.0.0.0 10.1.1.100 0.0.0.0 UG 0 0 0
eth0

I have also crosscable connection of R1 to another R2 with routing
table
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
eth0
172.16.1.0 0.0.0.0 255.255.255.0 UG 0 0 0 eth1
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
lo
0.0.0.0 10.1.1.1 0.0.0.0 UG 0 0 0
eth0

[Removed comp.protocols.tcp-ip since it isn't relevant]

I guess I should have asked for ifconfig -a in the same post -
newsreader won't let me go back and look at original. Anyway
> Routing table for hostA
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use
> Iface
> 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
> eth0
> 172.16.1.0 192.168.1.1 255.255.255.0 UG 0 0 0
> eth0
OK but redundant, since it is covered by the default route.
> 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0
> eth0
So eth0 has an IP addr of 192.168.1.x where x != 1, and is connected by
a crossover cable to eth1 on R1. eth1 on R1 has address 192.168.1.1.
OK so far?

> Routing table for R1
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use
> Iface
> 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
> eth1
> 172.16.1.0 0.0.0.0 255.255.255.0 UG 0 0 0 eth0
Redundant.
> 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
> eth0
> 0.0.0.0 10.1.1.100 0.0.0.0 UG 0 0 0
> eth0
eth1 had address 192.168.1.1 and is connected to A.
eth0 has address 10.1.1.1 and is connected to R2. More on this later.
>
> I have also crosscable connection of R1 to another R2 with routing
> table
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use
> Iface
> 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
> eth0
> 172.16.1.0 0.0.0.0 255.255.255.0 UG 0 0 0 eth1
> 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
> eth0
> 0.0.0.0 10.1.1.1 0.0.0.0 UG 0 0 0
> eth0
eth0 has address 10.1.1.100 and is connected to R1 via crossover cable?
I see several things wrong with this. First, R1 and R2 send default
traffic to each other. Second, it would be more usual to use a netmask
of 255.255.255.0 for the 10.1.1.0 network. Third, I don't understand
how the 192.168.1 entry got here or what it is supposed to be doing.
(There are two wildly different networks assigned to the same interface
with no gateway on either entry.) The 172.16.1.0 entry looks funny too.
What is the address of eth1 supposed to be?


I think you need to sit down with a piece of paper and draw your
network. For each network segment (each crossover cable is one) write
in the interface name, the addresses of each interface, the network
address, the broadcast address and the netmask. Then double check that
the routing tables and addresses (output of ifconfig -a or equivalent)
match the diagram.

This shouldn't be the cause of your problem but the 172.16.1.0 routes
on R1 and R2 have the flags UG which indicate that the route is Up and
uses a Gateway but there is no gateway defined.

Post the interface configurations for each machine from ifconfig also.
Also, please detail which interfaces are connected to which other
interfaces. i.e. Is eth0 on HostA connected to eth1 on R1?

Run tcpdump while you try to ping R1 from HostA and vice versa. Post
the results.

If your networks looks anything like this...

default (network 172.16.1.0/24)
^
| 172.16.1.A
+---+---+
| 1 |
| | R2
| 0 |
+---+---+
| 10.1.1.100
|
| 10.1.1.1
+---+---+
| 0 |
| | R1
| 1 |
+---+---+
| 192.168.1.1
|
| 192.168.1.100
+---+---+
| 0 |
| | A
| |
+-------+

then your routing tables should be like this:

A routing table
Destination Gateway Genmask Iface
192.168.1.0 0.0.0.0 255.255.255.0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 lo
0.0.0.0 192.168.1.1 0.0.0.0 eth0

R1 routing table
Destination Gateway Genmask Iface
192.168.1.0 0.0.0.0 255.255.255.0 eth1
10.0.0.0 0.0.0.0 255.0.0.0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 lo
0.0.0.0 10.1.1.100 0.0.0.0 eth0

R2 routing table
Destination Gateway Genmask Iface
172.16.1.0 0.0.0.0 255.255.255.0 eth1
10.0.0.0 0.0.0.0 255.0.0.0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 lo
192.168.1.0 10.1.1.1 0.0.0.0 eth0
0.0.0.0 172.16.1.B 0.0.0.0 eth0

hello,
I have set a 4 pc private LAN. Please give me the routing table
configurations for each of following 4 linux Pc's which are directly
connected using 3 crossover cable as
HostA on eth0 to Router1 on eth1
Router1 on eth0 to Router2 on eth0
HostB on eth0 to Router2 on eth1
Please forget my above postings configuration

HostA=>
eth0 Link encap:Ethernet HWaddr 00:08:A1:43:62:91
inet addr:192.168.1.100 Bcast:192.168.1.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4 errors:0 dropped:0 overruns:0 frame:0
TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:240 (240.0 b) TX bytes:240 (240.0 b)
Interrupt:11 Base address:0xbc00

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:2 errors:0 dropped:0 overruns:0 frame:0
TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:196 (196.0 b) TX bytes:196 (196.0 b)
Router1=>
eth0 Link encap:Ethernet HWaddr 00:80:48:C3:11:94
inet addr:10.1.1.100 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:110647 errors:0 dropped:0 overruns:0 frame:0
TX packets:97 errors:0 dropped:0 overruns:0 carrier:0
collisions:1 txqueuelen:1000
RX bytes:6839310 (6.5 Mb) TX bytes:6715 (6.5 Kb)
Interrupt:11 Base address:0xdc00

eth1 Link encap:Ethernet HWaddr 00:08:A1:43:61:F5
inet addr:192.168.1.1 Bcast:192.168.1.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:33 errors:0 dropped:0 overruns:0 frame:0
TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3494 (3.4 Kb) TX bytes:2246 (2.1 Kb)
Interrupt:9 Base address:0x9c00

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
Router2=>
eth0 Link encap:Ethernet HWaddr 00:08:A1:43:61:3F
inet addr:10.1.1.1 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:54 errors:0 dropped:0 overruns:0 frame:0
TX packets:50 errors:0 dropped:0 overruns:0 carrier:0
collisions:3 txqueuelen:1000
RX bytes:3759 (3.6 Kb) TX bytes:9012 (8.8 Kb)
Interrupt:11 Base address:0xf800

eth1 Link encap:Ethernet HWaddr 00:50:FC:4D:318
inet addr:172.16.1.1 Bcast:172.16.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:40 errors:0 dropped:0 overruns:0 frame:0
TX packets:30 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4045 (3.9 Kb) TX bytes:2384 (2.3 Kb)
Interrupt:11 Base address:0x3c00

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)

HostB=>
eth0 Link encap:Ethernet HWaddr 00:08:A1:43:61:F8
inet addr:172.16.1.100 Bcast:172.16.1.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:3 errors:0 dropped:0 overruns:0 frame:0
TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:180 (180.0 b) TX bytes:240 (240.0 b)
Interrupt:9 Base address:0x6c00

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:10 errors:0 dropped:0 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:700 (700.0 b) TX bytes:700 (700.0 b)

(E-Mail Removed) wrote:
> hello,
> I have set a 4 pc private LAN. Please give me the routing table
> configurations for each of following 4 linux Pc's which are directly
> connected using 3 crossover cable as
> HostA on eth0 to Router1 on eth1
> Router1 on eth0 to Router2 on eth0
> HostB on eth0 to Router2 on eth1
> Please forget my above postings configuration
>
> HostA=>
> eth0 addr:192.168.1.100 Bcast:192.168.1.255 Mask:255.255.255.0
>
> Router1=>
> eth0 addr:10.1.1.100 Bcast:10.255.255.255 Mask:255.0.0.0
> eth1 addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
>
> Router2=>
> eth0 addr:10.1.1.1 Bcast:10.255.255.255 Mask:255.0.0.0
> eth1 addr:172.16.1.1 Bcast:172.16.1.255 Mask:255.255.255.0
>
> HostB=>
> eth0 addr:172.16.1.100 Bcast:172.16.1.255 Mask:255.255.255.0

No connection to the outside ? Oh well, here's the answer to your home
assignment.

+-------+
| | ifconfig eth0 192.168.1.100 ...
| | A route add default gw 192.168.1.1
| 0 |
+---+---+
| 192.168.1.100
|
| 192.168.1.1
+---+---+
| 1 | ifconfig eth0 10.1.1.100 ...
| | R1 ifconfig eth1 192.168.1.1 ...
| 0 | route add -net 172.16.1.1/24 gw 10.1.1.1
+---+---+
| 10.1.1.100
|
| 10.1.1.1
+---+---+
| 0 | ifconfig eth0 10.1.1.1 ...
| | R2 ifconfig eth1 172.16.1.1 ...
| 1 | route add -net 192.168.1.0/24 gw 10.1.1.100
+---+---+
| 172.16.1.1
|
| 172.16.1.100
+---+---+
| 0 | ifconfig eth0 172.16.1.100 ...
| | B route add default gw 172.16.1.1
| |
+-------+