Table of Contents

Chapter 1 IP Address Configuration. 1-1

1.1 IP Address Overview. 1-1

1.1.1 IP Address Classification and Representation. 1-1

1.1.2 Subnet and Mask. 1-3

1.2 Configuring an IP Address. 1-3

1.3 Configuring an IP Address for a VLAN Interface. 1-4

1.4 Displaying IP Address Configuration. 1-4

1.5 IP Address Configuration Example. 1-5

1.6 Troubleshooting. 1-5

Chapter 2 IP Performance Configuration. 2-1

2.1 IP Performance Configuration. 2-1

2.1.1 Introduction to IP Performance Configuration. 2-1

2.1.2 Introduction to FIB. 2-1

2.1.3 TCP Attributes Configuration. 2-1

2.1.4 Subnet-Directed Broadcast Suppression Configuration. 2-2

2.2 Displaying and Maintaining IP Performance. 2-2

2.3 Troubleshooting. 2-4

 

Chapter 1  IP Address Configuration

1.1  IP Address Overview

1.1.1  IP Address Classification and Representation

An IP address is a 32-bit address allocated to a device connected to the Internet. It consists of two fields: net-id and host-id. To facilitate IP address management, IP addresses are divided into five classes, as shown in Figure 1-1.

Figure 1-1 Five classes of IP addresses

Class A, Class B, and Class C IP addresses are unicast addresses. Class D IP addresses are multicast addresses and Class E addresses are reserved for future special use. The first three types are commonly used.

IP addresses are in the dotted decimal notation. Each IP address contains four decimal integers, with each integer corresponding to one byte (for example,10.110.50.101).

Some IP addresses are reserved for special use. The IP address ranges that can be used by users are listed in Table 1-1.

Table 1-1 Classes and ranges of IP addresses

Network type	Address range	IP network range available for users	Description
A	0.0.0.0 to 127.255.255.255	1.0.0.0 to 126.0.0.0	l       An IP address with all 0s host ID is a network address and is used for network routing. l      An IP address with all 1s host ID is a broadcast address and is used for broadcast to all hosts on the network. l      The IP address 0.0.0.0 is used by hosts when they are booted but is not used afterward. l      An IP address with all 0s network ID represents a specific host on the local network and can be used as a source address but cannot be used as a destination address. l      All the IP addresses in the format of 127.X.Y.Z are reserved for loopback test and the packets sent to these addresses will not be output to lines; instead, they are processed internally and regarded as incoming packets.
B	128.0.0.0 to 191.255.255.255	128.0.0.0 to 191.254.0.0	l      An IP address with all 0s host ID is a network address and is used for network routing. l      An IP address with all 1s host ID is a broadcast address and is used for broadcast to all hosts on the network.
C	192.0.0.0 to 223.255.255.255	192.0.0.0 to 223.255.254.0	l      An IP address with all 0s host ID is a network address and is used for network routing. l      An IP address with all 1s host ID is a broadcast address and is used for broadcast to all hosts on the network.
D	224.0.0.0 to 239.255.255.255	None	Class D addresses are multicast addresses.
E	240.0.0.0 to 255.255.255.254	None	These IP addresses are reserved for future use.
Others	255.255.255.255	255.255.255.255	255.255.255.255 is used as a LAN broadcast address.

 

1.1.2  Subnet and Mask

The traditional IP address classification method wastes IP addresses greatly. In order to make full use of the available IP addresses, the concepts of mask and subnet were introduced.

A mask is a 32-bit number corresponding to an IP address. The number consists of 1s and 0s. These 1s and 0s can be arbitrarily combined in principle. However, a mask is usually defined as follows: the bits of the network number and subnet number are set to 1, and the bits of the host number are set to 0. The mask divides the IP address into two parts: subnet address and host address. In an IP address, the part corresponding to the "1" bits in the mask is the subnet address, and the part corresponding to the remaining "0" bits in the mask is the host address. If there is no subnet division, the subnet mask uses the default value. In this case, the length of 1s in the mask is equal to the net-id length. Therefore, for IP addresses of classes A, B and C, the default values of the corresponding subnet masks are 255.0.0.0, 255.255.0.0 and 255.255.255.0 respectively.

The mask can be used to divide a Class A network containing more than 16,000,000 hosts or a Class B network containing more than 60,000 hosts into multiple small networks. Each small network is called a subnet. For example, for the Class B network address 138.38.0.0, the mask 255.255.224.0 can be used to divide the network into eight subnets: 138.38.0.0, 138.38.32.0, 138.38.64.0, 138.38.96.0, 138.38.128.0, 138.38.160.0, 138.38.192.0 and 138.38.224.0 (see Figure 1-2). Each subnet can contain more than 8000 hosts.

Figure 1-2 Subnet division of the IP address

1.2  Configuring an IP Address

For a VLAN interface, an IP address can be obtained in one of the three ways:

l           Manually configured by using the IP address configuration command

l           Allocated by the BOOTP server

l           Allocated by the DHCP server

The three methods are mutually exclusive and the use of a new method will result in the IP address obtained by the old method being released. For example, if you obtain an IP address by using the IP address configuration command, and then use the ip address bootp-alloc command to apply for an IP address, the originally configured IP address is deleted and a new IP address will be allocated by BOOTP for the VLAN interface.

This chapter only introduces how to configure an IP address with the IP address configuration command. For the other two methods, refer to the “Management VLAN Configuration” module.

1.3  Configuring an IP Address for a VLAN Interface

Generally, it is enough to configure one IP address for a VLAN interface. However, you can configure up to five IP addresses for a VLAN interface so that the interface can be connected to several subnets. Among these IP addresses, one is the primary IP address and the others are secondary ones.

Table 1-2 Configure an IP address for a VLAN interface

Operation	Command	Description
Enter system view	system-view	—
Enter VLAN interface view	interface Vlan-interface vlan-id	—
Configure an IP address for a VLAN interface	ip address ip-address { mask | mask-length } [ sub ]	Required By default, a VLAN interface has no IP address. After an IP address is assigned to the VLAN interface through BOOTP or DHCP, you cannot configure a secondary IP address for the VLAN interface.

 

1.4  Displaying IP Address Configuration

After the above configuration, you can execute the display command in any view to display the operating status and configuration on the interface to verify your configuration.

Table 1-3 Display IP address configuration

Operation	Command	Description
Display VLAN interface information	display ip interface [ brief [ interface-type [ interface-number ] ] | [ interface-type interface-number ] ]	You can execute the display command in any view.

 

1.5  IP Address Configuration Example

I. Network requirements

Set the IP address and subnet mask of VLAN-interface1 to 129.2.2.1 and 255.255.255.0 respectively.

II. Network diagram

Figure 1-3 IP address configuration

III. Configuration procedure

# Configure an IP address for VLAN-interface1.

<H3C> system-view

[H3C] interface Vlan-interface 1

[H3C-Vlan-interface1] ip address 129.2.2.1 255.255.255.0

1.6  Troubleshooting

Symptom: The switch cannot ping the host directly-connected to a port.

Solution: You can perform troubleshooting as follows:

l           Check the configuration of the switch, and then use the display arp command to check whether the host has an corresponding ARP entry in the ARP table maintained by the Switch.

l           Check the VLAN that includes the switch port connecting the host. Check whether the VLAN has been configured with the VLAN interface. Then check whether the IP addresses of the VLAN interface and the host are on the same network segment.

l           If the configuration is correct, enable ARP debugging on the switch, and check whether the switch can correctly send and receive ARP packets. If it can only send but cannot receive ARP packets, errors may occur at the Ethernet physical layer.

 

Chapter 2  IP Performance Configuration

2.1  IP Performance Configuration

2.1.1  Introduction to IP Performance Configuration

IP performance configuration mainly refers to TCP attribute configuration. The TCP attributes that can be configured include:

l           synwait timer: This timer is started when TCP sends a syn packet. If no response packet is received before the timer times out, the TCP connection will be terminated. The timeout time of the synwait timer ranges from 2 to 600 seconds and is 75 seconds by default.

l           finwait timer: This timer is started when the TCP connection turns from the FIN_WAIT_1 state to the FIN_WAIT_2 state. If no FIN packet is received before the timer times out, the TCP connection will be terminated. The timeout time of the finwait timer ranges from 76 to 3,600 seconds and is 675 seconds by default.

l           The connection-oriented socket receive/send buffer size ranges from 1 to 32 KB and is 8 KB by default.

2.1.2  Introduction to FIB

Every switch stores a forwarding information base (FIB). FIB is used to store the forwarding information of the switch and guide Layer 3 packet forwarding.

You can know the forwarding information of the switch through the FIB table. Each FIB entry includes: destination address/mask length, next hop, current flag, timestamp, and outbound interface.

When the switch is running normally, the contents of the FIB and the routing table are the same. For routing and routing tables, refer to the “Routing Protocol” module of this manual.

2.1.3  TCP Attributes Configuration

Table 2-1 Configure TCP attributes

Operation	Command	Description
Enter system view	system-view	—
Configure timeout time for the synwait timer in TCP	tcp timer syn-timeout time-value	Required By default, the timeout time of the TCP synwait timer is 75 seconds.
Configure timeout time for the finwait timer in TCP	tcp timer fin-timeout time-value	Required By default, the timeout time of the TCP finwait timer is 675 seconds.
Configure the socket receive/send buffer size of TCP	tcp window window-size	Required By default, the receive/send buffer size is 8 KB.

 

2.1.4  Subnet-Directed Broadcast Suppression Configuration

Broadcast packets include the general broadcast packets and the subnet-directed broadcast packets. For a subnet-directed broadcast packet, its destination IP address is a sub network address, but its source IP address is not in this sub network segment.

You can perform the following configuration to determine whether to receive the subnet-directed broadcast packets.

Table 2-2 Configure to receive subnet-directed broadcast packets

Operation	Command	Description
Enter system view	system-view	—
Receive subnet-directed broadcast packets	ip forward-broadcast	Optional By default, the subnet-directed packets will be suppressed.

 

2.2  Displaying and Maintaining IP Performance

After the above configurations, you can execute the display command in any view to display the running status to verify your IP performance configuration.

Table 2-3 Display IP performance

Operation	Command	Description
Display TCP connection status	display tcp status	You can execute the display command in any view.
Display TCP connection statistics	display tcp statistics
Display UDP traffic statistics	display udp statistics
Display IP traffic statistics	display ip statistics
Display ICMP traffic statistics	display icmp statistics
Display the current socket information of the system	display ip socket [ socktype sock-type ] [ task-id socket-id ]
Display the forwarding information base (FIB) entries	display fib
Display the FIB entries matching the destination IP address	display fib ip_address1 [ { mask1 | mask-length1 } [ ip_address2 { mask2 | mask-length2 } | longer ] | longer ]
Display the FIB entries filtering through a specific ACL	display fib acl number
Display the FIB entries in the buffer which begin with, include or exclude the specified character string.	display fib | { begin | include | exclude } text
Display the FIB entries filtering through a specific prefix list	display fib ip-prefix listname
Display the total number of the FIB entries	display fib statistics

 

Use the reset command in user view to clear the IP, TCP, and UDP traffic statistics.

Table 2-4 Maintain IP performance

Configuration	Command	Description
Clear IP traffic statistics	reset ip statistics	You can execute the reset command in user view.
Clear TCP traffic statistics	reset tcp statistics
Clear UDP traffic statistics	reset udp statistics

 

2.3  Troubleshooting

Symptom: IP packets are forwarded normally, but TCP and UDP cannot work normally.

Solution: Enable the corresponding debugging information output to view the debugging information.

l           Use the display command to display the IP performance and check whether the PC runs normally.

l           Use the terminal debugging command to enable debugging information to be output to the console.

l           Use the debugging udp packet command to enable the UDP debugging to trace UDP packets.

<H3C> terminal debugging

<H3C> debugging udp packet

The UDP packets are shown in the following format:

UDP output packet:

Source IP address:202.38.160.1

Source port:1024

Destination IP Address 202.38.160.1

Destination port: 4296

l           Use the debugging tcp packet command to enable the TCP debugging to trace TCP packets.

<H3C> terminal debugging

<H3C> debugging tcp packet

Then the TCP packets received or sent will be displayed in the following format in real time:

TCP output packet:

Source IP address:202.38.160.1

Source port:1024

Destination IP Address 202.38.160.1

Destination port: 4296

Sequence number :4185089

Ack number: 0

Flag  :SYN

Packet length :60

Data offset: 10