Basic Router Configuration
Default Configuration
When you boot up your Cisco router for the first time, you notice some basic configuration has already been performed. Use the show running-configcommand to view the initial configuration, as shown in the following example.
Router# show running-config
Building configuration...
Current configuration : 723 bytes
!
version 12.4
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router
!
boot-start-marker
boot-end-marker
!
logging message-counter syslog
!
no aaa new-model
!
no ipv6 cef
ip source-route
ip cef
!
!
!
!
multilink bundle-name authenticated
!
!
archive
log config
hidekeys
!
!
!
!
!
interface GigabitEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface GigabitEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface GigabitEthernet0/2
no ip address
shutdown
duplex auto
speed auto
!
ip forward-protocol nd
!
no ip http server
!
!
!
!
!
control-plane
!
!
line con 0
line aux 0
line vty 0 3
login
!
exception data-corruption buffer truncate
scheduler allocate 20000 1000
end
Configuring Global Parameters
To configure the global parameters for your router, follow these steps.
SUMMARY STEPS
1. 
configure terminal
configure terminal
2. hostname name
hostname name
3. enable secret password
enable secret password
4. no ip domain-lookup
no ip domain-lookupDETAILED STEPS
For complete information on global parameter commands, see the Cisco IOS Release configuration guide documentation set.
Configuring I/O Memory Allocation
To reallocate the percentage of DRAM in use for I/O memory and processor memory on Cisco 3925E and Cisco 3945E routers, use the memory-size iomem i/o-memory-percentage command in global configuration mode. To revert to the default memory allocation, use the no form of this command. This procedure enables smartinit.
Tip We recommend that you configure the memory-size iomem below 25%. Any value above 25% should be used only for enhancing IPSec performance.
We recommend that you configure the memory-size iomem below 25%. Any value above 25% should be used only for enhancing IPSec performance.
When you specify the percentage of I/O memory in the command line, the processor memory automatically acquires the remaining percentage of DRAM memory.
Example
The following example allocates 25% of the DRAM memory to I/O memory and the remaining 75% to processor memory:
Router#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# memory-size iomem 5
IO memory size too small: minimum IO memory size is 201M
Router(config)#
Router(config)# memory-size iomem ?
<5-50> percentage of DRAM to use for I/O memory: 5, 10, 15, 20, 25, 30, 40, 50
Router(config)# memory-size iomem 25
Smart-init will be disabled and new I/O memory size will take effect upon reload.
Router(config)# end
Verifying IOMEM Setting
Router# show run
Current configuration : 6590 bytes
!
! Last configuration change at 16:48:41 UTC Tue Feb 23 2010 !
version 15.1
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
service internal
!
hostname Router1
!
!
no aaa new-model
!
memory-size iomem 25
!
Interface Ports
Table 7 lists the interfaces that are supported on Cisco 3900 series, 2900 series, and 1900 series integrated services routers.
Slots, Ports, Logical Interface, Interfaces
|
1941
|
29011
|
2911 & 2921
|
2951 & 3925 & 3945
|
3925E & 3945E
|
|---|---|---|---|---|---|
Onboard GE ports
|
Gi0/0,Gi0/1
|
Gi0/0,Gi0/1
|
Gi0/0,Gi0/1,GI0/2
|
Gi0/0,Gi0/1,GI0/2
|
Gi0/0,Gi0/1,GI0/2, GI0/3
|
Onboard WLAN
|
Wlan-ap0
|
not supported
|
not supported
|
not supported
|
not supported
|
Onboard WLAN GE connection to MGF2
|
Wlan-Gi0/0
|
not supported
|
not supported
|
not supported
|
not supported
|
Onboard ISM GE interface on the PCIe
|
service-module-name-ISM 0/0
|
service-module-
name-ISM 0/0 |
service-module-
name-ISM 0/0 |
service-module-
name-ISM 0/0 |
not supported
|
Onboard ISM GE connection to MGF
|
service-module-name-ISM 0/1
|
service-module-
name-ISM 0/1 |
service-module-
name-ISM 0/1 |
service-module-
name-ISM 0/1 |
not supported
|
USB
|
usbflash0, usbflash1
usbtoken0, usbtoken1
|
usbflash0, usbflash1
usbtoken0, usbtoken1
|
usbflash0, usbflash1
usbtoken0, usbtoken1
|
usbflash0, usbflash1
usbtoken0, usbtoken1
|
usbflash0, usbflash1
usbtoken0, usbtoken1
|
Interfaces on HWIC and VWIC
|
interface0/0/ port
interface0/1/ port |
interface0/0/port
interface0/1/port interface0/2/port interface0/3/port |
interface0/0/port
interface0/1/port interface0/2/port interface 0/3/port |
interface0/0/port
interface0/1/port interface0/2/port interface 0/3/port |
<int>0/0/<port>
<int>0/1/<port> <int>0/2/<port> |
Interfaces on Double Wide-HWIC
|
interface0/1
port |
interface0/1/port
interface0/3/port
|
interface0/1/port
interface0/3/port
|
interface0/1/port
interface0/3/port
|
<int>0/1/<port>
|
Interfaces on SM
|
not supported
|
not supported
|
interface1/port
|
interface1-2/port
interface1-4/port | |
Interfaces on Double Wide-SM
|
not supported
|
not supported
|
not supported
|
interface 2/port
interface 4/port | |
Interfaces HWIC on SM
Interfaces VWIC on SM
|
not supported
|
not supported
|
interface1wic-slot/port
|
interface1-2/wic-
slot/port7
interface1-4/wic-
slot/port8 |
interface1-2/wic-
slot/port interface1-4/wic- slot/port |
1 On the Cisco 2901 router, the numbering format for configuring an asynchronous interface is 0/slot/port. To configure the line associated with an asynchronous interface, simply use the interface number to specify the asynchronous line. For example, line 0/1/0 specifies the line associated with interface serial 0/1/0 on a WIC-2A/S in slot 1. Similarly, line 0/2/1 specifies the line associated with interface async 0/2/1 on a WIC-2AM in slot 2.
2 MGF = multi-gigabit fabric
3 Applies only to Cisco 2951, Cisco 3925, and Cisco 3925E routers.
4 Applies only to Cisco 3945 and Cisco 3945E routers.
5 Applies only to Cisco 2951, Cisco 3925, and Cisco 3925E routers.
6 Applies only to Cisco 3945 and Cisco 3945E routers.
7 Applies only to Cisco 2951, Cisco 3925, and Cisco 3925E routers.
8 Applies only to Cisco 3945 and Cisco 3945E routers.
|
Configuring Gigabit Ethernet Interfaces
To manually define onboard Gigabit Ethernet (GE) interfaces, follow these steps, beginning in global configuration mode.
SUMMARY STEPS
1. interface gigabitethernet slot/port
interface gigabitethernet slot/port
2. ip address ip-address mask
ip address ip-address mask
3. no shutdown
no shutdown
4. exit
exitDETAILED STEPS
Configuring Wireless LAN Interfaces
The wireless LAN interface on the Cisco 1941W router enables connection to the router through interface wlan-ap0. For more information about configuring a wireless connection, see the "Configuring the Wireless Device" section.
Configuring Interface Card and Module Interfaces
To configure interface cards and modules inserted in internal services module (ISM), enhanced high-speed WAN interface card (EHWIC), Ethernet WAN interface card (EWIC), and service module (SM) slots, see the appropriate interface card or module configuration documents on Cisco.com.
Configuring a Loopback Interface
The loopback interface acts as a placeholder for the static IP address and provides default routing information.
For complete information on the loopback commands, see the Cisco IOS Release configuration guide documentation set.
To configure a loopback interface, follow these steps, beginning in global configuration mode.
SUMMARY STEPS
1. interface type number
interface type number
2. ip address ip-address mask
ip address ip-address mask
3. exit
exitDETAILED STEPS
Example
The loopback interface in this sample configuration is used to support Network Address Translation (NAT) on the virtual-template interface. This configuration example shows the loopback interface configured on the gigabit ethernet interface with an IP address of 200.200.100.1/24, which acts as a static IP address. The loopback interface points back to virtual-template1, which has a negotiated IP address.
!
interface loopback 0
ip address 200.200.100.1 255.255.255.0 (static IP address)
ip nat outside
!
interface Virtual-Template1
ip unnumbered loopback0
no ip directed-broadcast
ip nat outside
!
Verifying Configuration
To verify that you have properly configured the loopback interface, enter the show interface loopback command. You should see verification output similar to the following example.
Router# show interface loopback 0
Loopback0 is up, line protocol is up
Hardware is Loopback
Internet address is 200.200.100.1/24
MTU 1514 bytes, BW 8000000 Kbit, DLY 5000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation LOOPBACK, loopback not set
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/0, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
Another way to verify the loopback interface is to ping it:
Router# ping 200.200.100.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 200.200.100.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
Configuring Command-Line Access
To configure parameters to control access to the router, follow these steps, beginning in global configuration mode.
SUMMARY STEPS
1. line [aux | console | tty | vty] line-number
line [aux | console | tty | vty] line-number
2. password password
password password
3. login
login
4. exec-timeout minutes [seconds]
exec-timeout minutes [seconds]
5. line [aux | console | tty | vty] line-number
line [aux | console | tty | vty] line-number
6. password password
password password
7. login
login
8. end
endDETAILED STEPS
Example
The following configuration shows the command-line access commands.
You do not need to input the commands marked "default." These commands appear automatically in the configuration file generated when you use theshow running-config command.
!
line con 0
exec-timeout 10 0
password 4youreyesonly
login
transport input none (default)
stopbits 1 (default)
line vty 0 4
password secret
login
!
Configuring Static Routes
Static routes provide fixed routing paths through the network. They are manually configured on the router. If the network topology changes, the static route must be updated with a new route. Static routes are private routes unless they are redistributed by a routing protocol.
To configure static routes, follow these steps, beginning in global configuration mode.
SUMMARY STEPS
1. ip route prefix mask {ip-address | interface-type interface-number [ip-address]}
ip route prefix mask {ip-address | interface-type interface-number [ip-address]}
2. end
endDETAILED STEPS
Command
|
Purpose
| |
|---|---|---|
Step 1
|
ip route prefix mask {ip-address | interface-typeinterface-number [ip-address]}
Example:
Router(config)# ip route 192.168.1.0 255.255.0.0 10.10.10.2
Router(config)#
|
Specifies the static route for the IP packets.
For details about this command and about additional parameters that can be set, see Cisco IOS IP Command Reference, Volume 2 of 4: Routing Protocols, Release 12.3
|
Step 2
|
end
Example:
Router(config)# end
Router#
|
Exits router configuration mode, and enters privileged EXEC mode.
|
Example
In the following configuration example, the static route sends out all IP packets with a destination IP address of 192.168.1.0 and a subnet mask of 255.255.255.0 on the Gigabit Ethernet interface to another device with an IP address of 10.10.10.2. Specifically, the packets are sent to the configured PVC.
You do not need to enter the command marked "(default)." This command appears automatically in the configuration file generated when you use theshow running-config command.
!
ip classless (default)
ip route 192.168.1.0 255.255.255.0 10.10.10.2!
Verifying Configuration
To verify that you have properly configured static routing, enter the show ip route command and look for static routes signified by the "S."
You should see verification output similar to the following:
Router# show ip route
Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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
10.0.0.0/24 is subnetted, 1 subnets
C 10.108.1.0 is directly connected, Loopback0
S* 0.0.0.0/0 is directly connected, FastEthernet0
Configuring Dynamic Routes
In dynamic routing, the network protocol adjusts the path automatically, based on network traffic or topology. Changes in dynamic routes are shared with other routers in the network.
The Cisco routers can use IP routing protocols, such as Routing Information Protocol (RIP) or Enhanced Interior Gateway Routing Protocol (EIGRP), to learn routes dynamically. You can configure either of these routing protocols on your router.
Configuring Routing Information Protocol
To configure the RIP routing protocol on the router, follow these steps, beginning in global configuration mode.
SUMMARY STEPS
1. router rip
router rip
2. version {1 | 2}
version {1 | 2}
3. network ip-address
network ip-address
4. no auto-summary
no auto-summary
5. end
endDETAILED STEPS
Example
The following configuration example shows RIP version 2 enabled in IP network 10.0.0.0 and 192.168.1.0.
To see this configuration, use the show running-config command from privileged EXEC mode.
!
Router# show running-config
router rip
version 2
network 10.0.0.0
network 192.168.1.0
no auto-summary
!
Verifying Configuration
To verify that you have properly configured RIP, enter the show ip route command and look for RIP routes signified by "R." You should see a verification output like the example shown below.
Router# show ip route
Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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
10.0.0.0/24 is subnetted, 1 subnets
C 10.108.1.0 is directly connected, Loopback0
R 3.0.0.0/8 [120/1] via 2.2.2.1, 00:00:02, Ethernet0/0
Configuring Enhanced Interior Gateway Routing Protocol
To configure Enhanced Interior Gateway Routing Protocol GRP (EGRP), follow these steps, beginning in global configuration mode.
SUMMARY STEPS
1. router eigrp as-number
router eigrp as-number
2. network ip-address
network ip-address
3. end
endDETAILED STEPS
Example
The following configuration example shows the EIGRP routing protocol enabled in IP networks 192.145.1.0 and 10.10.12.115. The EIGRP autonomous system number is 109.
To see this configuration use the show running-config command, beginning in privileged EXEC mode.
Router# show running-config
...
!
router eigrp 109
network 192.145.1.0
network 10.10.12.115
!
...
Verifying Configuration
To verify that you have properly configured IP EIGRP, enter the show ip route command, and look for EIGRP routes indicated by "D." You should see verification output similar to the following:
Router# show ip route
Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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
10.0.0.0/24 is subnetted, 1 subnets
C 10.108.1.0 is directly connected, Loopback0
D 3.0.0.0/8 [90/409600] via 2.2.2.1, 00:00:02, Ethernet0/0
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