IP address command directory

arp

arp timeout

clear arp-cache

ip address

ip directed-broadcast

ip forward-protocol udp

ip helper-address

ip host

ip proxy-arp

ip unnumbered

ping

show arp

show hosts

show ip interface

 

You can use command in this chapter to configure and check the addressing of IP network. If you want to know more information about the configuration of IP addressing, please refer to chapter “the configuration of IP addressing”.

arp

When configuring static ARP map, the static ARP map will be permanently saved in ARP cache. If you want to delete the configured static ARP map, use command “no arp”.

arp ip-address hardware-address [alias]

no arp ip-address

          

Parameter:

ip-address

IP address of local data link interface.

hardware-address

Physical address of local data link interface.

alias

(Optional) the router responds to the ARP request of this IP address, just like it owns this IP address.

 

Default:

Permanent ARP map does not exist in ARP cache.

Command mode:

global configuration mode

Explanation:

All general hosts can support dynamic ARP analysis, so generally user does not need to specifically configure static ARP map for the host.

Example:

The following command configures the MAC address of host with IP address of 1.1.1.1 as 00:12:34:56:78:90.

arp 1.1.1.1 00:12:34:56:78:90

 

Ralated command:

clear arp-cache

arp timeout

Configure the duration of dynamic ARP entry in ARP cache. If you want to reset it to default value, use command no arp timeout or default arp timeout.

arp timeout seconds

no arp timeout

default arp timeout

 

Parameter:

seconds

Duration (second) of dynamic ARP entry in ARP cache. 0 means that ARP cache dynamically resoluted from this interface will not be released timeout.

 

Default:

14400 seconds (4 hours)

Command mode:

Interface configuration mode

 

Explanation:   

If you do not configure on interface without (withARP, then the configuration will not be effective.

Command “show interface” will display the ARP entry timeout configured on this interface, it is shown as follows:

ARP type: ARPA, ARP timeout 04:00:00

 

Example:

The following command configures the duration of dynamic ARP map as 900 seconds on interface Ethernet 1/0, in order to more quickly refresh ARP cache.

interface ethernet 1/0

arp timeout 900

 

Ralated command:

show interface

clear arp-cache

Clear all dynamic ARP cache.

clear arp-cache

 

Parameter:

none

 

Command mode:

Supervisor mode

 

Example:

The following command clears all dynamic ARP caches.

clear arp-cache

 

Ralated command:

arp

ip address

Configure interface IP address, meanwhile configure network mask. Currently we do not classify A.B.C IP addresses seriously, yet do not use multicast address and broadcast address (all “1” for host part). Except Ethernet, various interfaces of other types can be on the same network. But, network configured on the Ethernet interface cannot be the same as any types of interfaces, except unnumbered interfaces . Normally you can configure one  primary address and infinite secondary addresses on one interface. Secondary  address can only be configured after the configuration of primary address, you can only delete primary address after delete all secondary address. IP address generated by the system itself, if the upper layer application does not designate the source address, the router will use the IP address on the same network as the gateway and configured on the outgoing interface, as the source address, if you are not sure about this IP address (such as interface router), then you can use the primary address of the outgoing interface. If one interface is not a configured IP address, and is not unnumbered interface, then this interface does not process IP packet.

If you want to delete an IP address, or stop the IP packet processing by a certain interface, you can use command “no ip address” to clear one or all IP addresses on the interface.

 

ip address ip-address mask [secondary]

no ip address ip-address mask

no ip address

 

Parameter:

ip-address

IP address

mask

IP network mask

secondary

(optional) Designate that it is a configured IP secondary address, if there is no designation,  it is a configured IP primary  address.

 

Default:

No configuration of any IP address on the interface

 

Command mode:

Interface configuration mode

 

Explanation:

If the router configures secondary IP address on certain physical segment, other systems on the same physical segment should also be configured the secondary address of the same logical network, or it will easily result in a route loop.

 

When using OSPFprotocol, you should guarantee that the secondary address and its primary address are in the same OSPF area.

 

 

Example:

The following command configures the primary address 202.0.0.1, network mask 255.255.255.0 on Ethernet 1/0 interface, in addition, configures two IP secondary address 203.0.0.1 and 204.0.0.1.

  interface ethernet1/0

ip address 202.0.0.1 255.255.255.0

ip address 203.0.0.1 255.255.255.0 secondary

ip address 204.0.0.1 255.255.255.0 secondary

ip directed-broadcast

Forward IP direct broadcast, and send the packet in physical broadcast form.

ip directed-broadcast [access-list-namer]

no ip directed-broadcast

 

Parameter:

access-list-name

(Optional) access list name. If the access list is defined, only the broadcast packet permits by the access list will be forwarded.

 

Default:

It does not forward IP direct broadcast by default.

 

Command mode:

Interface configuration mode

 

Example:

The following example configures forwarding of IP direct broadcast on interface ethernet1/0.

interface ethernet 1/0

ip directed-broadcast

ip forward-protocol

When the interface is configured ip helper-address, used to designate that which UDP protocol limited broadcast packets should be forwarded.

ip forward-protocol udp [port]

no ip forward-protocol udp [port]

default ip forward-protocol udp

 

Parameter:

port          (Optional) the destination port which needs forwarded UDP packets.

 

Default:

Forward the NETBIOS name service packet.

 

Command mode:

global configuration mode

 

Explanation:

Forward NETBIOS name service packet by default currently, if you do not want it to forward NETBIOS name service packet, you can use any of these commands:

no ip forward-protocol udp netbios-ns

no ip forward-protocol udp 137

Use the following command to stop all UDP limited broadcast packet:

no ip forward-protocol udp

 

Example:

Router_config#ip forward-protocol udp 137

 

相关命令:

ip helper-address

ip helper-address

Forward the IP directed broadcast packets to the IP helper address designated by the command, it can be unicast or broadcast address. Each interface can be configured many helper addresses.

ip helper-address address

no ip helper-address [address]

 

Parameter:

address              IP helper address

 

Default:

IP helper address not configured

 

Command mode:

Interface configuration mode

 

Explanation:

This command is not effective on X.25 interface, because the router can not discern physical broadcast.

 

Example:

The following command configures IP helper address 1.0.0.1 on interface Ethernet 1/0.

interface ethernet 1/0

ip helper-address 1.0.0.1

 

Ralated command:

ip forward-protocol udp

ip host

Define static host name-address map. If you want to delete host name-address map, use command “no ip host”.

ip host name address

no ip host name

 

Parameter:

name          Host name

Address           IP address.

 

Default:

No maps configured

 

Command mode:

global configuration mode

 

Example:

The following example configures the host name as dns-server with IP address 202.96.1.3.

ip host dns-server 202.96.1.3

ip proxy-arp

To enable Agent ARP on the interface. If you want to close this function, use command “no ip proxy arp”.

ip proxy-arp

no ip proxy-arp

 

Parameter:

none

 

Default:

Agent ARP.

 

Command mode:

Interface configuration mode

 

Explanation:

When the router receives ARP request, if the router has a route to the address requests IP, and the routing interface is different from the interface received request, the router will send ARP response from its own MAC address, then, when it receives actual data packets, it forwards. So, even a host does not fully realize the topological structure of the network, or it is not configured the correct(exact) route, and can communicate with the remote port. For it, remote host directly connects with it in the same physical subnetwork.

If the host requires the router to provide this service, it should be in the same IP network as the router is, or, at least its IP address should make the router consider them in the same IP subnetwork, that is to say, it can use different masks. Or, the router will not provide this service.

 

Example:

The following example turns on the function of agent ARP on interface ethernet1/0:

interface ethernet 1/0

ip proxy-arp

ip unnumbered

Configure an interface as an interface with unnumbered, you can start IP process function without configuration of IP address. In order to stop IP process on this interface, use command “no ip  unnumbered”.

ip unnumbered type number

no ip unnumbered

 

Parameter:

type number

The type and number of another interface configured IP address. This interface cannot be unnumbered interface using IP address of other interface.

 

Default:

This function not started.

Command mode:

Interface configuration mode

 

Explanation:

For point-to-point link interface, you can start IP process on this interface with this command instead of configuring the exclusive IP address, and designate valid IP address on other interfaces as the source address for this interface to send packet, in order to save IP address. This kind of point-to-point interface can be called unnumbered interface. The IP packet generated on unnumbered interface, such as routing refresh packet, will use the valid IP address configured on the designated interface in the command. It also uses this address to make sure that which routing processes send update packets on this interface. But, it has the following restrictions:

1.  Serial interface and tunnel interface encapsulated by HDLC, PPP, LAPB, SLIP and frame relay can be configured as unnumbered interface with this command. But, X.25 and SMDS interface cannot use this command.

2.  No way to check whether this interface could normally operating by command “ping”. You can use “SNMP” to check the mode of this interface remotely.

This command can be realized according to the restriction that the interface cannot configure valid IP address in RFC1195.

This command can be realized according to the restriction that the interface cannot configure valid IP address in RFC1195.

 

Example:

The following command configures interface serial1/0 as unnumbered interface, uses valid IP address 1.0.0.1 configured on interface ethernet1/1 as the source address to send packet on this interface:

interface ethernet 1/1

ip address 1.0.0.1 255.255.255.0

interface serial 1/0

ip unnumbered ethernet 1/0

ping

Check the availability of the host and the connectivity of the network. This is achieved by sending ICMP response request packet to the opposite port, and wait for ICMP response packet from opposite port.

ping [-f] [-i {source-ip-address ][-m {source-interface}] [-j host1 [host2 host3 …]] [–k host1 [host2, host3 …]] [-l length] [-n number] [-r hops] [-s tos] [-t ttl] [-v] [-w waittime] host

Parameter:

-f

Place DF (non-fragrant packet) position. If he packet the user wants to send is greater than path MTU, the packet will be scattered by the router on the path, and send ICMP error packet to source host. If you find a network performance problem, it may be caused by smaller MTU configured on one of the nodes. You can use this option to define the minimum MTU on the path.

default:Position not placed

-I

Set the source IP address default:

Send main IP address of the interface.

source-ip-address

The packet uses source-ip-address as source IP address

-m

Set the IP address of certain interface adopted by the packets

source-interface

The packet uses IP address on source-interface interface as the source address.

-j host1 [host2 host3…]

Set loose source router.

default:Not configured.

-k host1 [host2 host3…]

Set serious source router.

default:Not configured.

-l length

Set the length of ICMP data in the packet.

default:556 bytes.

-n number

Set the number of total packet sent

default:5 packets.

-r hops

Record routes, record hops routes maximum.

default:Do not record the route.

-s tos

Set IP TOS of packet as tos.

default:0

-t ttl

Set IP TTL of the packet as ttl.

default:255

-v

Detailed output.

default:Brief output.

-w waittime

Response time to wait for each packet.

default:2 seconds.

host  

Destination host.

 

Command mode:

Configure mode, global configuration mode and interface configuration mode

 

Explanation:

Command “ping” supports destination address of broadcast address and multicast address. If it is limited broadcast (255.255.255.255) or multicast address, it will send ICMP response request packet on all available interfaces support broadcast or multicast. The router will output addresses of all response hosts. The user can directly acquire all hosts support multicast convert on directly connected session by a ping of multicast address 224.0.0.1.

IF you want to stop the ping, press “q” or “Q”.

Brief output by default:

Character

Description

!

Receive a response packet.

.

It does not receive a response in the timeout.

U

It receives ICMP destination unreachable packet

Q

It receives ICMP source refrain packet.

R

It receives ICMP redirect packet.

T

It receives ICMP timeout packet.

P

It receives ICMP parameter problem packet.

Statistical information output:

Output

Description

packets transmitted

Packets sent.

packets received

Packets received, not including other ICMP packets.

packet loss

Packet percentage not responded.

round-trip min/avg/max

Minimum/average/maximum trip time (mille-second)

 

Example:

Router#ping -l 10000 -n 30 192.168.20.125

PING 192.168.20.125 (192.168.20.125): 10000 data bytes

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

--- 192.168.20.125 ping statistics ---

30 packets transmitted, 30 packets received, 0% packet loss

round-trip min/avg/max = 50/64/110 ms

show arp

Show all ARP entrys(entries), including ARP map of interface IP address, static ARP map, dynamic ARP map configured by the user.

show arp

 

Parameter:

none

          

Command mode:

Supervisor mode

 

Explanation:

Displayed information includes:

Protocol

Type of network address maps physical address, such as IP.

Address

Address, network address maps physical address, such as IP address.

Age

Survival time, the time between the generation and current of ARP entry, minute as the unit. The router use this ARP entry will not affect this value.

Hardware Address

Physical address, the physical address corresponds to the network address, for irresoluted entry the value is empty.

Type

Type, means the packet encapsulation type used by the interface, including ARPA, SNAP and etc…

Interface

Interface, the interface related to this network address.

 

Example:

The following command shows ARP cache

router#show arp

Protocol   IP Address      Age(min)  Hardware Address   Type  Interface

   IP     192.168.20.77         11   00:30:80:d5:37:e0  ARPA  Ethernet1/0

   IP     192.168.20.33          0     Incomplete

   IP     192.168.20.22          -   08:00:3e:33:33:8a  ARPA  Ethernet1/0

   IP     192.168.20.124         0   00:a0:24:9e:53:36  ARPA  Ethernet1/0

   IP     192.168.0.22           -   08:00:3e:33:33:8b  ARPA  Ethernet1/1

show hosts

Show host name—all entrys in address cache.

show hosts

 

Parameter:

This command has no parameter or keyword.

 

Command mode:

Configure mode

 

Example:

The following command displays all host name/address map

show hosts

 

Ralated command:

clear host

show ip interface

Show IP configuration on the interface.

show ip interface [type number]

 

Parameter:

type     

(Optional) interface type

number

(Optional) interface serial.

 

Command mode:

Configure mode

 

Explanation:

If the link layer of the interface can effectively send or receive data, it is a usable interface and the mode is “protocol up”. If you configure IP address on this interface, the router will add a directly connected route in the routing table. If the link layer protocol disconnects, which is “protocol down”, this directly connected route will be deleted. If you designate interface type and serial, it only displays interface information. Or, it displays IP configuration information of all interfaces.

Example:

The following command shows the IP configuration on interface f0/0:

Router#show ip interface e0/1

    Ethernet1/0 is up, line protocol is up

     IP address : 192.168.20.167/24
        Broadcast address : 192.168.20.255
        Helper address : not set
        MTU : 1500(byte)
        Forward Directed broadcast : OFF
        Multicast reserved groups joined:
          224.0.0.9 224.0.0.6 224.0.0.5 224.0.0.2
          224.0.0.1
        Outgoing ACL : not set
        Incoming ACL : not set
        IP fast switching : ON
        IP fast switching on the same interface : OFF
        ICMP unreachables : ON
        ICMP mask replies : OFF
        ICMP redirects : ON

 

   

Show description:

Domain

Description

FastEthernet0/0 is up

If the interface hardware is usable, the interface is tagged “up”. If the interface is usable, its hardware and line protocol must all be “up”.

line protocol is up

If the interface can provide intercommunication, its line protocol would be tagged “up”. If the interface is usable, both the interface hardware and line protocol must be “up”.

Internet address

Interface IP address and network mask.

Broadcast address

Show broadcast address.

MTU

Show IP MTU configured on the interface.

Helper address

Show helper address/

Directed broadcast forwarding

Whether to forward directed broadcast packet.

Multicast reserved groups joined

Reserved multicast group interface joined

Outgoing access list

Outgoing access control list used by the interface.

Inbound access list

Inbound access control list used by the interface.

Proxy ARP

Whether the interface supports proxy ARP

ICMP redirects

Whether to send ICMP redirect packet on the interface

ICMP unreachables

Whether to send ICMP unreachable packets on the interface

ICMP mask replies

Whether to send ICMP mask reply packets on the interface.