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SubjectWeird problem with routing
Hi,

I have alot of linux boxes with 3 NIC's, one for the main LAN and one for doing
testing (they send stuff to devices and check the replies) Anyhow, we want to use
the ISC dhcp client for testing a DHCP server. What I see happening is this:

/---------\
+------------------------+---------+ Sniffer |
| eth0 | eth0 \---------/
| box1 | box2
/------+------\ /------+------\
| 172.128.1.1 | | 172.128.1.2 +------> dhcp
\-------------/ \-------------/ eth2 server

ISC DHCP 2.0b1pl28
Linux Kernel 2.0.36

start dhclient on eth2 on box2

dhclient add's a route to 0.0.0.0/0.0.0.0 via eth2, this is okay, but then weird
things start happening to the other interfaces, for example, I ping out the eth0
of box2 to box1 and sniff the traffic on the main LAN and I see the pings, but
the mac address it is sending the ping to is it's own address!

This just seems wrong, surely there is something broken here?

Ifconfig, route table and Packet Dump follow:

>>>>>>>>>>> OUTPUT OF IFCONFIG

lo Link encap:Local Loopback
inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0
UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1
RX packets:89 errors:0 dropped:0 overruns:0 frame:0
TX packets:89 errors:0 dropped:0 overruns:0 carrier:0
collisions:0

eth0 Link encap:Ethernet HWaddr 00:00:B4:97:FD:8E
inet addr:202.49.72.77 Bcast:202.49.72.95 Mask:255.255.255.224
IPX/Ethernet 802.3 addr:C0E7230E:0000B497FD8E
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:199065 errors:0 dropped:0 overruns:0 frame:0
TX packets:192266 errors:0 dropped:0 overruns:0 carrier:0
collisions:710
Interrupt:9 Base address:0xe400

eth1 Link encap:Ethernet HWaddr 00:00:B4:98:06:70
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
IPX/Ethernet 802.3 addr:C0E72345:0000B4980670
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:220590 errors:0 dropped:0 overruns:0 frame:0
TX packets:226986 errors:0 dropped:0 overruns:0 carrier:0
collisions:854
Interrupt:12 Base address:0xe000

eth2 Link encap:Ethernet HWaddr 00:00:B4:97:FD:63
inet addr:0.0.0.0 Bcast:255.255.255.255 Mask:0.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:3 dropped:0 overruns:0 carrier:6
collisions:51
Interrupt:10 Base address:0xd800

>>>>>>>>> OUTPUT OF ROUTE TABLE

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
202.49.72.64 0.0.0.0 255.255.255.224 U 0 0 5 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 2 eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 1 lo
0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 3 eth2
0.0.0.0 202.49.72.94 0.0.0.0 UG 0 0 2 eth0

>>>>>>>> PACKET DUMP FROM SNIFFER

Packet Number : 1 02:26:57 PM
Length : 102 bytes
ether: ==================== Ethernet Datalink Layer ====================
Station: 00-00-B4-97-FD-8E ----> 00-00-B4-97-FD-8E
Type: 0x0800 (IP)
ip: ======================= Internet Protocol =======================
Station:202.49.72.77 ---->202.49.72.92
Protocol: ICMP
Version: 4
Header Length (32 bit words): 5
Precedence: Routine
Normal Delay, Normal Throughput, Normal Reliability
Total length: 84
Identification: 1761
Fragmentation allowed, Last fragment
Fragment Offset: 0
Time to Live: 64 seconds
Checksum: 0x4EBC(Valid)
icmp: =============== Internet Control Message Protocol ===============
Type: Echo Request
Checksum: 0xD063(Valid)
Code: 0
Identifier: 57090
Sequence Number: 0
Data:
0: 10 E6 1B 37 2D 79 04 00 08 09 0A 0B 0C 0D 0E 0F |...7-y..........
10: 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F |................
20: 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F | !"#$%&'()*+,-./
30: 30 31 32 33 34 35 36 37 |01234567

Packet Number : 2 02:26:58 PM
Length : 102 bytes
ether: ==================== Ethernet Datalink Layer ====================
Station: 00-00-B4-97-FD-8E ----> 00-00-B4-97-FD-8E
Type: 0x0800 (IP)
ip: ======================= Internet Protocol =======================
Station:202.49.72.77 ---->202.49.72.92
Protocol: ICMP
Version: 4
Header Length (32 bit words): 5
Precedence: Routine
Normal Delay, Normal Throughput, Normal Reliability
Total length: 84
Identification: 1762
Fragmentation allowed, Last fragment
Fragment Offset: 0
Time to Live: 64 seconds
Checksum: 0x4EBB(Valid)
icmp: =============== Internet Control Message Protocol ===============
Type: Echo Request
Checksum: 0x0A71(Valid)
Code: 0
Identifier: 57090
Sequence Number: 256
Data:
0: 11 E6 1B 37 F1 6B 04 00 08 09 0A 0B 0C 0D 0E 0F |...7.k..........
10: 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F |................
20: 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F | !"#$%&'()*+,-./
30: 30 31 32 33 34 35 36 37 |01234567

Packet Number : 3 02:26:59 PM
Length : 102 bytes
ether: ==================== Ethernet Datalink Layer ====================
Station: 00-00-B4-97-FD-8E ----> 00-00-B4-97-FD-8E
Type: 0x0800 (IP)
ip: ======================= Internet Protocol =======================
Station:202.49.72.77 ---->202.49.72.92
Protocol: ICMP
Version: 4
Header Length (32 bit words): 5
Precedence: Routine
Normal Delay, Normal Throughput, Normal Reliability
Total length: 84
Identification: 1763
Fragmentation allowed, Last fragment
Fragment Offset: 0
Time to Live: 64 seconds
Checksum: 0x4EBA(Valid)
icmp: =============== Internet Control Message Protocol ===============
Type: Echo Request
Checksum: 0x0B71(Valid)
Code: 0
Identifier: 57090
Sequence Number: 512
Data:
0: 12 E6 1B 37 EE 6B 04 00 08 09 0A 0B 0C 0D 0E 0F |...7.k..........
10: 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F |................
20: 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F | !"#$%&'()*+,-./
30: 30 31 32 33 34 35 36 37 |01234567

Packet Number : 4 02:27:00 PM
Length : 102 bytes
ether: ==================== Ethernet Datalink Layer ====================
Station: 00-00-B4-97-FD-8E ----> 00-00-B4-97-FD-8E
Type: 0x0800 (IP)
ip: ======================= Internet Protocol =======================
Station:202.49.72.77 ---->202.49.72.92
Protocol: ICMP
Version: 4
Header Length (32 bit words): 5
Precedence: Routine
Normal Delay, Normal Throughput, Normal Reliability
Total length: 84
Identification: 1764
Fragmentation allowed, Last fragment
Fragment Offset: 0
Time to Live: 64 seconds
Checksum: 0x4EB9(Valid)
icmp: =============== Internet Control Message Protocol ===============
Type: Echo Request
Checksum: 0x0371(Valid)
Code: 0
Identifier: 57090
Sequence Number: 768
Data:
0: 13 E6 1B 37 F4 6B 04 00 08 09 0A 0B 0C 0D 0E 0F |...7.k..........
10: 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F |................
20: 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F | !"#$%&'()*+,-./
30: 30 31 32 33 34 35 36 37 |01234567

If you have any questions, please email me and I will answer as best I can.


Thanks,
Patrick


--
Patrick Jordan-Smith,
System Test Engineer,
Teltrend (NZ) Ltd.
Phone +64-3-377-8900
Fax +64-3-377-8870

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