I have a project that includes a firewall and two routers. I have created two subnetworks with VLSM for both routers and I have a cable that represents a serial connection between them. The firewall should be between the internet and the first router that I have used. I have no trouble about pinging routers' ethernet interfaces and serial connections, I think my network is working well. However, I can connect to the Internet from firewall but cannot access it from the other routers. Here is my firewall and network configuration:


-Ethernet 0/1 is connected to the router-1 with a cat5 cable. This port's IP address is'll see it is a part of the network that is created for router-1) -Ethernet 0/0 is connected to the Internet.


-Ethernet 0/0 port has the IP -Serial 0/0 port has the IP


-Ethernet 0/0 port has the IP -Serial 0/0 port has the IP

PS:I have used RIPv2 on all devices.

Like I said, I can connect to the Internet from the fw but cannot from the routers. Thanks ^_^.

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    Aug 11, 2017 at 17:36

2 Answers 2


Just for clarity I am assuming your layout is:

Internet - FW - - r1 - - r2 -

You mention that you are running a routing protocol (RIPv2) on all devices. Assuming that includes the firewall and all things are configured correctly the firewall should have a route back to the other 2 networks ( & Can you confirm that you can ping these from the firewall?

You state that you can ping all interfaces on both routers but you don't specify the source you are pinging from.

You don't mention a default route in your routers so I will guess that is where the problem lies. If your routing protocol is operating properly your firewall is going to be a node hanging off of the network. If you don't specifically tell R1 and R2 to utilize it as the default they won't. Here is a document on the Cisco website on the subject:

Gateway of last resort.

  • Gateway of last resort is to network is variably subnetted, 3 subnets, 3 masks C is directly connected, Ethernet0/0 R [120/1] via, 00:00:16, Serial0/0 C is directly connected, Serial0/0 S* [1/0] via Ankara#ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) This is I see when I try to ping.
    – Fake Hesap
    Jun 25, 2015 at 7:29
  • So that looks like route table and ping results from R1. If you can ping from FW to R2 then I think the problem must exist in your firewall. Does it have any capabilites to packet trace? I would start a packet trace on the inside interface and watch the packets arrive and then jump over to the outside interface to verify that the are arriving at the firewall but not being forwarded/routed/NATed. More than likely you will have a problem in one of those areas. Jun 25, 2015 at 17:01

Firt of all. You need to review your policies on the way to permit the traffic from inside to outside, and on the contrary way.

If that is OK, then you can check if your firewall know your LAN networks. I think your firewall do not know how to reach your networks, you need to check if it is also running RIPv2, the same that routers.

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