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Internet Gateway 192.168.0.201 Server 1 192.168.0.101 192.168.1.101 192.168.2.101 gateway: 192.168.0.201 VIP: 192.168.1.100 VIP: 192.168.2.100 Server 2 192.168.0.102 192.168.1.102 192.168.2.102 gateway: 192.168.0.201 Client 1 192.168.2.201 gateway: 192.168.2.100 From Client 1, I ...
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  1. #1
    Just Joined!
    Join Date
    Nov 2011
    Posts
    1

    routing question / problem


    Internet Gateway
    192.168.0.201

    Server 1
    192.168.0.101
    192.168.1.101
    192.168.2.101
    gateway: 192.168.0.201
    VIP: 192.168.1.100
    VIP: 192.168.2.100

    Server 2
    192.168.0.102
    192.168.1.102
    192.168.2.102
    gateway: 192.168.0.201

    Client 1
    192.168.2.201
    gateway: 192.168.2.100

    From Client 1, I can ping 192.168.2.102 (Server 2), this would make sense all three computers are on the same network. However, from client 1, I cannot ping or ssh to 192.168.1.102 (server 2). Why? I don't know. Using wireshark, I can see the ICMP echo request go through server 1 and pass to server 2. This path makes sense. I see the echo request being recieved on the 192.168.2.102 NIC on Server 2. But no response is sent out on either NIC on Server 2. Why?

    I have made no routing table modification on either server. I have IP forwarding set in sysctl.conf on both servers. I have iptables turned off. The only way I can ping from client 1 to 192.168.1.102 (server 2) is enabling masquerading in iptables on both servers on all interfaces. The question is: why can't client 1 ping to 192.168.1.102 with no modifications to any routing table and with the iptables service stopped?

  2. #2
    Linux Engineer Kloschüssel's Avatar
    Join Date
    Oct 2005
    Location
    Italy
    Posts
    773
    Where's the gateway 2.100? Does the gateway 0.201 route all packets for the subnets 0.0/24, 1.0/24 and 2.0/24? Are those second IP addresses physical connections?

    Generally speaking, it looks to me as if you're fighting against how the IP stack works. There are two possible solutions for hosts to communicate:

    1] Transparent access to either server: NAT (network address translation)
    Then you can connect to the router, which transparently redirects all packets to the right server.
    2] Route your packets from one network into the other
    Basically you reconfigure your router that sits between both networks to allow packets flowing from one network to the other by adding a static route.

    Cheers

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