In one of our data-centre we've a Debian machine acting as a router. From this network we cannot reach any of the machines found on 192.168.100.0/24 network. E.g The gateway on the 192.168.100.0/24 network is the 192.168.100.10. This gateway is not reachable from this network 192.168.200.0/24.
The network configuration is as follow
/etc/network/interfaces
auto lo eth0 eth1
iface lo inet loopback
# The primary network interface
allow-hotplug eth0
iface eth0 inet static
address 77.xx.xx.xx
netmask 255.255.255.240
gateway 77.xx.xx.xx
# The internal network interface
iface eth1 inet static
address 192.168.200.20
netmask 255.255.255.0
iface eth1.100 inet static
address 192.168.100.1
netmask 255.255.255.0
iface tun0 inet static
address 10.254.254.1
netmask 255.255.255.252
pointopoint 10.254.254.2
The ifconfig shows the following
eth0 Link encap:Ethernet HWaddr 00:13:21:ae:d7:23
inet addr:77.xx.xx.xx Bcast:77.xx.xx.xx Mask:255.255.255.240
inet6 addr: fe80::213:21ff:feae:d723/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:136897619 errors:7 dropped:0 overruns:0 frame:56
TX packets:35219565 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:106904749360 (99.5 GiB) TX bytes:4700046351 (4.3 GiB)
Interrupt:25
eth1 Link encap:Ethernet HWaddr 00:13:21:ae:d7:22
inet addr:192.168.200.20 Bcast:192.168.200.255 Mask:255.255.255.0
inet6 addr: fe80::213:21ff:feae:d722/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:25456278 errors:0 dropped:0 overruns:0 frame:0
TX packets:51273676 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2910299307 (2.7 GiB) TX bytes:71434605655 (66.5 GiB)
Interrupt:26
eth1.100 Link encap:Ethernet HWaddr 00:13:21:ae:d7:22
inet addr:192.168.100.1 Bcast:192.168.100.255 Mask:255.255.255.0
inet6 addr: fe80::213:21ff:feae:d722/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:1350 (1.3 KiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:8057 errors:0 dropped:0 overruns:0 frame:0
TX packets:8057 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:678439 (662.5 KiB) TX bytes:678439 (662.5 KiB)
ppp0 Link encap:Point-to-Point Protocol
inet addr:192.168.200.200 P-t-P:192.168.0.201 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1486 Metric:1
RX packets:16438 errors:0 dropped:0 overruns:0 frame:0
TX packets:31312 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:1281863 (1.2 MiB) TX bytes:14955384 (14.2 MiB)
I've tried to add one of the following routes manually but without success.
route add -net 192.168.100.0 netmask 255.255.255.0 dev eth1
route add -net 192.168.100.0 netmask 255.255.255.0 gw 192.168.200.20 dev eth1
ip route add 192.168.100.0/24 via 192.168.200.20 dev eth1
The route is being added but does not do much. The network 192.168.100.0/24 remains unreachable.
What ip route show and route -n shows
root@dc-dc:~# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.201 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0
77.xx.xx.xx 0.0.0.0 255.255.255.240 U 0 0 0 eth0
192.168.200.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
0.0.0.0 77.xx.xx.xx 0.0.0.0 UG 0 0 0 eth0
root@dc-dc:~# ip route show
192.168.0.201 dev ppp0 proto kernel scope link src 192.168.200.200
77.xx.xx.xx/28 dev eth0 proto kernel scope link src 77.xx.xx.xx
192.168.200.0/24 dev eth1 proto kernel scope link src 192.168.200.20
default via 77.xx.xx.xx dev eth0
Port forwarding is enabled
root@dc-dc:~# cat /proc/sys/net/ipv4/ip_forward
1
Output of iptables
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 DROP all -- eth0 * 220.xx.xx.2 0.0.0.0/0
57 2964 ACCEPT tcp -- eth0 * 194.xx.xx.0/24 0.0.0.0/0 tcp dpt:22
108K 6495K ACCEPT tcp -- eth0 * 194.xx.xx.0/24 0.0.0.0/0 tcp dpt:1723
52M 71G ACCEPT all -- eth0 * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
14M 724M ACCEPT all -- eth1 * 0.0.0.0/0 0.0.0.0/0
4407 427K ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0
26M 38G ACCEPT all -- ppp0 * 0.0.0.0/0 0.0.0.0/0
415 19592 ACCEPT tcp -- eth0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
249 11776 ACCEPT tcp -- eth0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
5 180 ACCEPT icmp -- eth0 * 0.0.0.0/0 0.0.0.0/0 icmp type 0
14351 1193K ACCEPT icmp -- eth0 * 0.0.0.0/0 0.0.0.0/0 icmp type 8
14092 845K ACCEPT all -- eth0 * 194.xx.xx.0/24 0.0.0.0/0
0 0 ACCEPT all -- * * 0.0.0.0/0 224.0.0.0/8
0 0 ACCEPT 112 -- * * 0.0.0.0/0 0.0.0.0/0
16173 1376K DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
6 616 ACCEPT all -- eth1 eth1 0.0.0.0/0 0.0.0.0/0
21M 31G ACCEPT all -- ppp0 * 0.0.0.0/0 0.0.0.0/0
10M 1573M ACCEPT all -- * ppp0 0.0.0.0/0 0.0.0.0/0
138K 20M ACCEPT all -- * eth0 0.0.0.0/0 0.0.0.0/0
146K 202M ACCEPT all -- eth0 * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
0 0 ACCEPT udp -- * * 89.xx.xx.xx 127.0.0.1 udp spt:53
0 0 ACCEPT udp -- * * 83.xx.xx.xx 127.0.0.1 udp spt:53
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
43M 41G ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT 112 -- * * 0.0.0.0/0 0.0.0.0/0
0 0 DROP all -- * * 0.0.0.0/0 0.0.0.0/0
root@dc-dc:~# iptables -t nat -L -v
Chain PREROUTING (policy ACCEPT 121K packets, 12M bytes)
pkts bytes target prot opt in out source destination
Chain POSTROUTING (policy ACCEPT 1715 packets, 112K bytes)
pkts bytes target prot opt in out source destination
0 0 MASQUERADE all -- any any 10.254.254.0/24 anywhere
0 0 MASQUERADE all -- any ppp0 anywhere anywhere
0 0 SNAT all -- any eth0 anywhere 212.159.203.234 to:194.50.96.11
58671 3659K MASQUERADE all -- any eth0 anywhere anywhere
Chain OUTPUT (policy ACCEPT 28351 packets, 1945K bytes)
pkts bytes target prot opt in out source destination
Any idea what I could try? Thanks in advance
is the connection to other networks, so the router itself working?
Are you sure the route for the reply is set correctly as well? If you set the gateway only for one direction, this is not enough, you also have to make sure the route in the opposite direction works.
for example:
you have server A connected to router A and then connected to server B. Let's assume both servers have a default gateway which is not router A, but some other router. Now if you tell server A that it's route to server B is via router A, this is not enough. You also need to tell server B that it's router to server A is via router A. Otherwise the packets from server A might arrive on server B, but server B doesn't know howto reply or uses a wrong router for the reply.
It looks like interface "eth1.100" was created with vconfig or similar. This means the interface will act as if it is tagged for VLAN 100, and any packets that are transmitted from it will have the 802.1Q VLAN tag added to it. The reason I suspect this is because the interface name is "eth1.100" rather than "eth1:100".
What you actually wanted was probably just multi-homing. Firstly get rid of the interface "eth1.100" with the command "vconfig rem eth1.100", then add 192.168.100.1 to eth1 simply by issuing the command "ifconfig eth1 add 192.168.100.1".
Hopefully this will resolve your issue.