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Firewall Deployment in Routed Mode

Chapter Description

You can deploy a Secure Firewall threat defense as a default gateway for your network so that the end users can use the threat defense to communicate with a different subnet or to connect to the Internet. This sample chapter from CCNP Security Cisco Secure Firewall and Intrusion Prevention System Official Cert Guide describes the processes to deploy a threat defense in routed mode.

Validation of Interface Configuration

After the configurations are deployed to the threat defense, the hosts between the inside network and outside network should be able to communicate successfully. To test connectivity, you can simply run an ICMP ping test between the inside and outside hosts. If the hosts are running any services (such as web or Secure Shell), you can also use them to verify connectivity.

In a brand-new deployment, the management center does not display connection events. If you would like to use your management center to validate any connection attempts through your threat defense, you need to enable logging in the access control policy. By default, a new access control policy does not come with any customizable access control rule. Because we describe the operation of an access control rule in later chapters, for now, you can add a simple access control rule to allow the traffic and enable logging within that rule (see Figure 4-13). Alternatively, in an access control policy without any rule, you can simply enable logging in the default action (see Figure 4-14), which can also trigger connection events.


FIGURE 4-13 Enabling Logging Within an Access Control Rule


FIGURE 4-14 Enabling Logging in an Access Control Policy as a Default Action

If you deployed the access control policy with logging functionality enabled, you can now view events for any associated connections by navigating to Analysis > Connections > Events of your management center.

Figure 4-15 exhibits connection attempts from an inside host (IP: to an outside host (IP: over ICMP, SSH, and HTTPS protocols.


FIGURE 4-15 Table View of Connection Events Between Inside and Outside Hosts

While you run ICMP traffic, you can view the details of how the system is processing the ICMP packets by using the debug command.

Example 4-6 shows ICMP requests and replies exchanged between two computers located in the inside and outside networks.

Example 4-6 Debugging ICMP Traffic in a Threat Defense

> debug icmp trace
debug icmp trace enabled at level 1
ID=4101 seq=1 len=56
ID=4101 seq=1 len=56
ID=4101 seq=2 len=56
ID=4101 seq=2 len=56
<Output Omitted>
> undebug all

If the ping test fails, you need to determine the status of the interfaces. You can run the following commands on the threat defense to determine the interface status and to verify the configurations you applied from the management center to the threat defense. Command outputs are slightly different depending on the configuration method (static versus dynamic).

  • show ip

  • show interface ip brief

  • show interface interface_ID

  • show running-config interface

Example 4-7 shows output of the show ip command. You can view the mapping between the interface, logical name, and IP address in this output. You cannot, however, view the current status in the output.

Example 4-7 Output of the show ip Command

> show ip
System IP Addresses:
Interface            Name                IP address    Subnet mask    Method
Current IP Addresses:
Interface            Name                IP address    Subnet mask    Method

Example 4-8 confirms that both the GigabitEthernet0/0 and GigabitEthernet0/1 interfaces are up and configured manually (using static IP addresses). The show interface ip brief command provides an overview, including the current status, of each of the interfaces.

Example 4-8 Overview of the Interface Status

> show interface ip brief
Interface               IP-Address     OK? Method Status            Protocol
GigabitEthernet0/0    YES CONFIG up                    up
GigabitEthernet0/1     YES CONFIG up                    up
GigabitEthernet0/2      unassigned     YES unset  administratively down up
GigabitEthernet0/3      unassigned     YES unset  administratively down up
GigabitEthernet0/4      unassigned     YES unset  administratively down up
GigabitEthernet0/5      unassigned     YES unset  administratively down up
GigabitEthernet0/6      unassigned     YES unset  administratively down up
GigabitEthernet0/7      unassigned     YES unset  administratively down up
Internal-Control0/0      YES unset  up                    up
Internal-Control0/1     unassigned     YES unset  up                    up
Internal-Data0/0        unassigned     YES unset  down                  up
Internal-Data0/0        unassigned     YES unset  up                    up
Internal-Data0/1    YES unset  up                    up
Internal-Data0/2        unassigned     YES unset  up                    up
Management0/0           unassigned     YES unset  up                    up

Example 4-9 shows detailed statistics of the GigabitEthernet0/0 interface. By using the show interface interface_ID command, you can determine any errors and drops that may have occurred on an interface.

Example 4-9 Detailed Statistics of Packets in the Interface Level
> show interface GigabitEthernet 0/0
Interface GigabitEthernet0/0 "INSIDE_INTERFACE", is up, line protocol is up
  Hardware is net_vmxnet3, BW 10000 Mbps, DLY 10 usec
        Auto-Duplex(Full-duplex), Auto-Speed(10000 Mbps)
        Input flow control is unsupported, output flow control is unsupported
        MAC address 000a.000b.abcd, MTU 1500
        IP address, subnet mask
        277 packets input, 60997 bytes, 0 no buffer
        Received 0 broadcasts, 0 runts, 0 giants
        0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
        0 pause input, 0 resume input
        0 L2 decode drops
        215 packets output, 77346 bytes, 0 underruns
        0 pause output, 0 resume output
        0 output errors, 0 collisions, 0 interface resets
        0 late collisions, 0 deferred
        0 input reset drops, 0 output reset drops
        input queue (blocks free curr/low): hardware (0/0)
        output queue (blocks free curr/low): hardware (0/0)
  Traffic Statistics for "INSIDE_INTERFACE":
        277 packets input, 57079 bytes
        215 packets output, 74336 bytes
        7 packets dropped
      1 minute input rate 0 pkts/sec,  0 bytes/sec
      1 minute output rate 0 pkts/sec,  0 bytes/sec
      1 minute drop rate, 0 pkts/sec
      5 minute input rate 0 pkts/sec,  0 bytes/sec
      5 minute output rate 0 pkts/sec,  0 bytes/sec
      5 minute drop rate, 0 pkts/sec

Example 4-10 displays the interface configurations from the CLI. You can find all the settings you configured on the management center and applied to the threat defense.

Example 4-10 Running Configurations of GigabitEthernet0/0 and GigabitEthernet0/1

> show running-config interface
interface GigabitEthernet0/0
 cts manual
  propagate sgt preserve-untag
  policy static sgt disabled trusted
 security-level 0
 ip address
interface GigabitEthernet0/1
 cts manual
  propagate sgt preserve-untag
  policy static sgt disabled trusted
 security-level 0
 ip address
interface GigabitEthernet0/2
 no nameif
 no security-level
 no ip address
<Output Omitted for Brevity>

If the threat defense does not offer an IP address to its DHCP clients, or if the threat defense cannot obtain an IP address from any external DHCP server, you can debug any DHCP transactions to and from the DHCP server.

Example 4-11 proves that the threat defense has dynamically assigned the IP address to a host with the MAC address C4:2C:03:3C:98:A8. This IP address is the first address from the DHCP address pool to

Example 4-11 Verifying the IP Address Assignment from a DHCP Address Pool

> show dhcpd binding
IP address   Client Identifier   Lease expiration    Type     c42c.033c.98a8       3580 seconds  Automatic

If you do not see any DHCP binding, you can debug the DHCP packets on the threat defense.

Example 4-12 demonstrates the process of a DHCP server assigning an IP address. In the debug output, you can analyze the four major stages of the DHCP protocol: Discovery, Offer, Request, and Acknowledgment (DORA).

Example 4-12 Exchange of DHCP Packets Between a Threat Defense and a DHCP Server
> debug dhcpd packet
debug dhcpd packet enabled at level 1
DHCPD/RA: Server msg received, fip=ANY, fport=0 on INSIDE_INTERFACE interface
DHCPD: DHCPDISCOVER received from client c42c.033c.98a8 on interface
DHCPD: send ping pkt to
DHCPD: ping got no response for ip:
DHCPD: Add binding to radix tree
DHCPD/RA: Binding successfully added to hash table
DHCPD: Sending DHCPOFFER to client c42c.033c.98a8 (
DHCPD: Total # of raw options copied to outgoing DHCP message is 0.
DHCPD/RA: creating ARP entry (, c42c.033c.98a8).
DHCPD: unicasting BOOTREPLY to client c42c.033c.98a8(
DHCPD/RA: Server msg received, fip=ANY, fport=0 on INSIDE_INTERFACE interface
DHCPD: DHCPREQUEST received from client c42c.033c.98a8.
DHCPD: Extracting client address from the message
DHCPD: Client c42c.033c.98a8 specified it’s address
DHCPD: Client is on the correct network
DHCPD: Client accepted our offer
DHCPD: Client and server agree on address
DHCPD: Renewing client c42c.033c.98a8 lease
DHCPD: Client lease can be renewed
DHCPD: Sending DHCPACK to client c42c.033c.98a8 (
DHCPD: Total # of raw options copied to outgoing DHCP message is 0.
DHCPD/RA: creating ARP entry (, c42c.033c.98a8).
DHCPD: unicasting BOOTREPLY to client c42c.033c.98a8(

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