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Basic Interface Configuration of Cisco ASA 5520

April 10 2013 , Written by Cisco & Cisco Router, Network Switch Published on #Cisco Switches - Cisco Firewall

The Cisco ASA 5520 is one of the mid-range ASAs. 4 Gigabit Ethernet ports. Max 450 Mbps throughput under ideal conditions. Good for mid-sized offices. Has an expansion slot where you can install an add-on card that does content filtering (e.g. email and web) or intrusion prevention. Or you can install an expansion card that gives your ASA more physical ports.

 

The lowest-end ASA is the Cisco ASA 5505 model, which is a more like a switch with VLANs. But on the 5510 models and up, interface config is akin to that of a router.

 

Factory Default Settings on the ASA 5520

Out of the box, or with the configure factory-default command, the ASA 5520 is configured thusly:

Interface

Name

Security Level

IP Address

State

GigabitEthernet0/0
GigabitEthernet0/1
GigabitEthernet0/2
GigabitEthernet0/3

no nameif

no security-level

no ip address

Shutdown

Management0/0

management

100

192.168.1.1

Management-only

 

Configuration Example

On a Cisco ASA 5520 with a factory default config, a show run interface coughs up this information:

interface GigabitEthernet0/0

 shutdown

 no nameif

 no security-level

 no ip address

!

interface GigabitEthernet0/1

 shutdown

 no nameif

 no security-level

 no ip address

!

interface GigabitEthernet0/2

 shutdown

 no nameif

 no security-level

 no ip address

!

interface GigabitEthernet0/3

 shutdown

 no nameif

 no security-level

 no ip address

!

interface Management0/0

 nameif management

 security-level 100

 ip address 192.168.1.1 255.255.255.0

 management-only

 

With nothing configured on the interfaces, the routing table on a factory default ASA shows only the loopback interface:

ciscoasa(config-if)# show route

 

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

       * - candidate default, U - per-user static route, o - ODR

       P - periodic downloaded static route

 

Gateway of last resort is not set

 

C    127.0.0.0 255.255.0.0 is directly connected, cplane

 

To make an interface operational, it needs a name, an IP address, a security level and it needs to be administratively brought up with the no shutdown command.

 

So let’s give the GigabitEthernet0/0 interface a name and an IP address.

ciscoasa# con t

ciscoasa(config)# interface gigabitEthernet 0/0

ciscoasa(config-if)# nameif outside

INFO: Security level for "outside" set to 0 by default.

ciscoasa(config-if)# ip address 5.5.5.1

 

When an interface is named “outside”, the ASA automatically assigns the interface a security level of 0. If an interface is named “inside”, it is automatically given a security level of 100.

To view the config on all interfaces, use the show run interface command. To view just one interface, use theshow run interface command and specify the interface:

ciscoasa(config-if)# sh ru int g 0/0

!

interface GigabitEthernet0/0

 shutdown

 nameif outside

 security-level 0

 ip address 5.5.5.1 255.0.0.0

 

Because I did not specify a subnet mask when I configured the IP address, the interface was automatically assigned a classful subnet mask. I can specify the subnet mask in the ip address command.

ciscoasa(config-if)# ip address 5.5.5.1 255.255.255.0

ciscoasa(config-if)# sh ru int g 0/0

!

interface GigabitEthernet0/0

 shutdown

 nameif outside

 security-level 0

 ip address 5.5.5.1 255.255.255.0

 

When I am ready to bring the interface up, I use the no shutdown command.

ciscoasa(config-if)# no shut

ciscoasa(config-if)# sh ru int g 0/0

!

interface GigabitEthernet0/0

 nameif outside

 security-level 0

 ip address 5.5.5.1 255.255.255.0

 

The show run ip address command shows all interfaces that have IP addresses.

ciscoasa(config-if)# sh ru ip

!

interface GigabitEthernet0/0

 nameif outside

 security-level 0

 ip address 5.5.5.1 255.255.255.0

!

interface Management0/0

 nameif management

 security-level 100

 ip address 192.168.1.1 255.255.255.0

The show ip address command also displays all IP addresses, along with the method used to configure the IP address. (“System IP Addresses” refer to the primary IP addresses used for failover. “Current IP Addresses” are the currently-used IP addresses on the interface(s). So, in an active/standby ASA pair, the active ASA would have the same “System” and “Current” IP addresses. The standby ASA would have different “System” and “Current” IP addresses.)

ciscoasa(config-if)# sh ip

System IP Addresses:

Interface                Name                   IP address      Subnet mask     Method

GigabitEthernet0/0       outside                5.5.5.1         255.255.255.0   manual

Management0/0            management             192.168.1.1     255.255.255.0   manual

Current IP Addresses:

Interface                Name                   IP address      Subnet mask     Method

GigabitEthernet0/0       outside                5.5.5.1         255.255.255.0   manual

Management0/0            management             192.168.1.1     255.255.255.0   manual

 

After a write memory and a reload, when you do show ip address, the “Method” on these manually-configured interfaces changes to CONFIG, signifying that they were loaded from the startup config:

ciscoasa# sh ip

System IP Addresses:

Interface                Name                   IP address      Subnet mask     Method

GigabitEthernet0/0       outside                5.5.5.1         255.255.255.0   CONFIG

Management0/0            management             192.168.1.1     255.255.255.0   CONFIG

Current IP Addresses:

Interface                Name                   IP address      Subnet mask     Method

GigabitEthernet0/0       outside                5.5.5.1         255.255.255.0   CONFIG

Management0/0            management             192.168.1.1     255.255.255.0   CONFIG

 

Now a show route command displays the directly-connected route to the 5.5.5.0 subnet.

ciscoasa(config-if)# sh ro

 

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

       * - candidate default, U - per-user static route, o - ODR

       P - periodic downloaded static route

 

Gateway of last resort is not set

 

C    5.5.5.0 255.255.255.0 is directly connected, outside

C    127.0.0.0 255.255.0.0 is directly connected, cplane

 

From the show run interface command, we can see that there is nothing configured on the g 0/1 interface. Let’s set it as a DHCP client and bring it up.

ciscoasa(config-if)# sh ru int g 0/1

!

interface GigabitEthernet0/1

 shutdown

 no nameif

 no security-level

 no ip address

ciscoasa(config-if)# nameif inside

INFO: Security level for "inside" set to 100 by default.

ciscoasa(config-if)# ip add dhcp

ciscoasa(config-if)# no shut

 

The show run interface command will show that g 0/1 is a DHCP client, but it will not display the dynamically-assigned IP address on the interface. To view the DHCP IP address, use the show ip address command.

ciscoasa(config-if)# sh ip add

System IP Addresses:

Interface                Name                   IP address      Subnet mask     Method

GigabitEthernet0/0       outside                5.5.5.1         255.255.255.0   CONFIG

GigabitEthernet0/1       inside                 10.30.1.101     255.255.255.0   DHCP

Management0/0            management             192.168.1.1     255.255.255.0   CONFIG

Current IP Addresses:

Interface                Name                   IP address      Subnet mask     Method

GigabitEthernet0/0       outside                5.5.5.1         255.255.255.0   CONFIG

GigabitEthernet0/1       inside                 10.30.1.101     255.255.255.0   DHCP

Management0/0            management             192.168.1.1     255.255.255.0   CONFIG

Note that the “Method” for g 0/1 is “DHCP”.

You can also display all IP addresses on all interfaces with the show interface ip brief command.

ciscoasa(config-if)# sh int ip b

Interface                  IP-Address      OK? Method Status                Protocol

GigabitEthernet0/0         5.5.5.1         YES CONFIG up                    up

GigabitEthernet0/1         10.30.1.101     YES DHCP   up                    up

GigabitEthernet0/2         unassigned      YES unset  administratively down down

GigabitEthernet0/3         unassigned      YES unset  administratively down down

Internal-Control0/0        127.0.1.1       YES unset  up                    up

Internal-Data0/0           unassigned      YES unset  up                    up

Management0/0              192.168.1.1     YES CONFIG down                  down

Virtual254                 unassigned      YES unset  up                    up

 

More Related Cisco ASA Tips:

Cisco ASA 5520 Basic Configuration Guide

Site-to-Site IPSEC VPN between Two Cisco ASA 5520

How to Configure Dual ISP on Cisco ASA 5505?

Cisco ASA 8.4 vs. Typical NAT/PAT Configuration

Eight Commands on a Cisco ASA Security Appliance You Should Know

VLAN Sub-Interfaces on Cisco ASA 5500 Firewall Configuration

How to Configure Cisco ASA 5505 Firewall?

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