H3C S3100-52P Operation Manual-Release 1602(V1.01)

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05-IP Address and Performance Operation
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Chapter 1  IP Addressing Configuration

When configuring IP addressing, go to these sections for information you are interested in:

l           IP Addressing Overview

l           Configuring IP Addresses

l           Displaying IP Addressing Configuration

l           IP Address Configuration Examples

1.1  IP Addressing Overview

1.1.1  IP Address Classes

IP addressing uses a 32-bit address to identify each host on a network. An example is 01010000100000001000000010000000 in binary. To make IP addresses in 32-bit form easier to read, they are written in dotted decimal notation, each being four octets in length, for example, 10.1.1.1 for the address just mentioned.

Each IP address breaks down into two parts:

l           Net ID: The first several bits of the IP address defining a network, also known as class bits.

l           Host ID: Identifies a host on a network.

For administration sake, IP addresses are divided into five classes, as shown in the following figure (in which the blue parts represent the address class).

Figure 1-1 IP address classes

Table 1-1 describes the address ranges of these five classes. Currently, the first three classes of IP addresses are used in quantity.

Table 1-1 IP address classes and ranges

Class

Address range

Description

A

0.0.0.0 to 127.255.255.255

Address 0.0.0.0 means this host no this network. This address is used by a host at bootstrap when it does not know its IP address. This address is never a valid destination address.

Addresses starting with 127 are reserved for loopback test. Packets destined to these addresses are processed locally as input packets rather than sent to the link.

B

128.0.0.0 to 191.255.255.255

––

C

192.0.0.0 to 223.255.255.255

––

D

224.0.0.0 to 239.255.255.255

Multicast address.

E

240.0.0.0 to 255.255.255.255

Reserved for future use except for the broadcast address 255.255.255.255.

 

1.1.2  Special Case IP Addresses

The following IP addresses are for special use, and they cannot be used as host IP addresses:

l           IP address with an all-zeros net ID: Identifies a host on the local network. For example, IP address 0.0.0.16 indicates the host with a host ID of 16 on the local network.

l           IP address with an all-zeros host ID: Identifies a network.

l           IP address with an all-ones host ID: Identifies a directed broadcast address. For example, a packet with the destination address of 192.168.1.255 will be broadcasted to all the hosts on the network 192.168.1.0.

1.1.3  Subnetting and Masking

Subnetting was developed to address the risk of IP address exhaustion resulting from fast expansion of the Internet. The idea is to break a network down into smaller networks called subnets by using some bits of the host ID to create a subnet ID. To identify the boundary between the host ID and the combination of net ID and subnet ID, masking is used.

Each subnet mask comprises 32 bits related to the corresponding bits in an IP address. In a subnet mask, the part containing consecutive ones identifies the combination of net ID and subnet ID whereas the part containing consecutive zeros identifies the host ID.

Figure 1-2 shows how a Class B network is subnetted.

Figure 1-2 Subnet a Class B network

While allowing you to create multiple logical networks within a single Class A, B, or C network, subnetting is transparent to the rest of the Internet. All these networks still appear as one. As subnetting adds an additional level, subnet ID, to the two-level hierarchy with IP addressing, IP routing now involves three steps: delivery to the site, delivery to the subnet, and delivery to the host.

In the absence of subnetting, some special addresses such as the addresses with the net ID of all zeros and the addresses with the host ID of all ones, are not assignable to hosts. The same is true of subnetting. When designing your network, you should note that subnetting is somewhat a tradeoff between subnets and accommodated hosts. For example, a Class B network can accommodate 65,534 (216 – 2. Of the two deducted Class B addresses, one with an all-ones host ID is the broadcast address and the other with an all-zeros host ID is the network address) hosts before being subnetted. After you break it down into 512 (29) subnets by using the first 9 bits of the host ID for the subnet, you have only 7 bits for the host ID and thus have only 126 (27 – 2) hosts in each subnet. The maximum number of hosts is thus 64,512 (512 × 126), 1022 less after the network is subnetted.

Class A, B, and C networks, before being subnetted, use these default masks (also called natural masks): 255.0.0.0, 255.255.0.0, and 255.255.255.0 respectively.

1.2  Configuring IP Addresses

An S3100-52P Ethernet Switch supports assigning IP addresses to VLAN interfaces and loopback interfaces. Besides directly assigning an IP address to a VLAN interface, you may configure a VLAN interface to obtain an IP address  through BOOTP or DHCP as alternatives. If you change the way an interface obtains an IP address, from manual assignment to BOOTP for example, the IP address obtained from BOOTP will overwrite the old one manually assigned.

 

&  Note:

This chapter only covers how to assign an IP address manually. For the other two approaches to IP address assignment, refer to the part discussing DHCP in this manual.

 

Follow these steps to configure an IP address to an interface:

To do…

Use the command…

Remarks

Enter system view

system-view

––

Enter interface view

interface interface-type interface-number

––

Assign an IP address to the Interface

ip address ip-address { mask | mask-length } [ sub ]

Required

No IP address is assigned by default.

 

&  Note:

l      You can assign at most two IP address to an interface, among which one is the primary IP address and the other is the secondary IP address. A newly specified primary IP address overwrites the previous one if there is any.

l      The primary and secondary IP addresses of an interface cannot reside on the same network segment; the IP address of a VLAN interface must not be on the same network segment as that of a loopback interface on a device.

l      A VLAN interface cannot be configured with a secondary IP address if the interface has been configured to obtain an IP address through BOOTP or DHCP.

 

1.3  Displaying IP Addressing Configuration

To do…

Use the command…

Remarks

Display information about a specified or all Layer 3 interfaces

display ip interface [ interface-type interface-number ]

Available in any view

Display brief configuration information about a specified or all Layer 3 interfaces

display ip interface brief [ interface-type [ interface-number ] ]

 

1.4  IP Address Configuration Examples

1.4.1  IP Address Configuration Example I

I. Network requirement

Assign IP address 129.2.2.1 with mask 255.255.255.0 to VLAN-interface 1 of the switch.

II. Network diagram

Figure 1-3 Network diagram for IP address configuration

III. Configuration procedure

# Configure an IP address for VLAN-interface 1.

<Switch> system-view

[Switch] interface Vlan-interface 1

[Switch-Vlan-interface1] ip address 129.2.2.1 255.255.255.0

1.4.2  IP Address Configuration Example II

I. Network requirements

As shown in Figure 1-4, VLAN-interface 1 on a switch is connected to a LAN comprising two segments: 172.16.1.0/24 and 172.16.2.0/24.

To enable the hosts on the two network segments to communicate with the external network through the switch, and the hosts on the LAN can communicate with each other, do the following:

l           Assign two IP addresses to VLAN-interface 1 on the switch.

l           Set the switch as the gateway on all PCs of the two networks.

II. Network diagram

Figure 1-4 Network diagram for IP address configuration

III. Configuration procedure

# Assign a primary IP address and a secondary IP address to VLAN-interface 1.

<Switch> system-view

[Switch] interface Vlan-interface 1

[Switch-Vlan-interface1] ip address 172.16.1.1 255.255.255.0

[Switch-Vlan-interface1] ip address 172.16.2.1 255.255.255.0 sub

# Set the gateway address to 172.16.1.1 on the PCs attached to the subnet 172.16.1.0/24, and to 172.16.2.1 on the PCs attached to the subnet 172.16.2.0/24.

# Ping a host on the subnet 172.16.1.0/24 from the switch to check the connectivity.

<Switch> ping 172.16.1.2

  PING 172.16.1.2: 56  data bytes, press CTRL_C to break

    Reply from 172.16.1.2: bytes=56 Sequence=1 ttl=255 time=25 ms

    Reply from 172.16.1.2: bytes=56 Sequence=2 ttl=255 time=27 ms

    Reply from 172.16.1.2: bytes=56 Sequence=3 ttl=255 time=26 ms

    Reply from 172.16.1.2: bytes=56 Sequence=4 ttl=255 time=26 ms

    Reply from 172.16.1.2: bytes=56 Sequence=5 ttl=255 time=26 ms

 

  --- 172.16.1.2 ping statistics ---

    5 packet(s) transmitted

    5 packet(s) received

    0.00% packet loss

    round-trip min/avg/max = 25/26/27 ms

The output information shows the switch can communicate with the hosts on the subnet 172.16.1.0/24.

# Ping a host on the subnet 172.16.2.0/24 from the switch to check the connectivity.

<Switch> ping 172.16.2.2

  PING 172.16.2.2: 56  data bytes, press CTRL_C to break

    Reply from 172.16.2.2: bytes=56 Sequence=1 ttl=255 time=25 ms

    Reply from 172.16.2.2: bytes=56 Sequence=2 ttl=255 time=26 ms

    Reply from 172.16.2.2: bytes=56 Sequence=3 ttl=255 time=26 ms

    Reply from 172.16.2.2: bytes=56 Sequence=4 ttl=255 time=26 ms

    Reply from 172.16.2.2: bytes=56 Sequence=5 ttl=255 time=26 ms

 

  --- 172.16.2.2 ping statistics ---

    5 packet(s) transmitted

    5 packet(s) received

    0.00% packet loss

    round-trip min/avg/max = 25/25/26 ms

The output information shows the switch can communicate with the hosts on the subnet 172.16.2.0/24.

 


Chapter 2  IP Performance Configuration

When configuring IP performance, go to these sections for information you are interested in:

l           IP Performance Overview

l           Configuring IP Performance

l           Displaying and Maintaining IP Performance Configuration

2.1  IP Performance Overview

2.1.1  Introduction to IP Performance Configuration

In some network environments, you need to adjust the IP parameters to achieve best network performance. The IP performance configuration supported by an S3100-52P Ethernet Switch includes:

l           Configuring TCP attributes

l           Enabling reception of directed broadcasts to a directly connected network

l           Disabling ICMP to send error packets

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.

2.2  Configuring IP Performance

2.2.1  IP Performance Configuration Task List

Complete the following tasks to configure IP performance:

Task

Remarks

Configuring TCP Attributes

Optional

Disabling ICMP to Send Error Packets

Optional

 

2.2.2  Configuring TCP Attributes

TCP optional parameters that can be configured include:

l           synwait timer: When sending a SYN packet, TCP starts the synwait timer. If no response packets are received before the synwait timer times out, the TCP connection is not successfully created.

l           finwait timer: When the TCP connection is changed into FIN_WAIT_2 state, finwait timer will be started. If no FIN packets are received within the timer timeout, the TCP connection will be terminated. If FIN packets are received, the TCP connection state changes to TIME_WAIT. If non-FIN packets are received, the system restarts the timer from receiving the last non-FIN packet. The connection is broken after the timer expires.

l           Size of TCP receive/send buffer

Follow these steps to configure TCP attributes:

To do…

Use the command…

Remarks

Enter system view

system-view

Configure TCP synwait timer’s timeout value

tcp timer syn-timeout time-value

Optional

75 seconds by default.

Configure TCP finwait timer’s timeout value

tcp timer fin-timeout time-value

Optional

675 seconds by default.

Configure the size of TCP receive/send buffer

tcp window window-size

Optional

8 kilobytes by default.

 

2.2.3  Disabling ICMP to Send Error Packets

Sending error packets is a major function of ICMP protocol. In case of network abnormalities, ICMP packets are usually sent by the network or transport layer protocols to notify corresponding devices so as to facilitate control and management.

Although sending ICMP error packets facilitate control and management, it still has the following disadvantages:

l           Sending a lot of ICMP packets will increase network traffic.

l           If receiving a lot of malicious packets that cause it to send ICMP error packets, the device’s performance will be reduced.

l           As the ICMP redirection function increases the routing table size of a host, the host’s performance will be reduced if its routing table becomes very large.

l           If a host sends malicious ICMP destination unreachable packets, end users may be affected.

You can disable the device from sending such ICMP error packets for reducing network traffic and preventing malicious attacks.

Follow these steps to disable sending ICMP error packets:

To do…

Use the command…

Remarks

Enter system view

system-view

Disable sending ICMP redirects

undo icmp redirect send

Required

Enabled by default.

Disable sending ICMP destination unreachable packets

undo icmp unreach send

Required

Enabled by default.

 

2.3  Displaying and Maintaining IP Performance Configuration

To do…

Use the command…

Remarks

Display TCP connection status

display tcp status

Available 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 } regular-expression

Display the total number of the FIB entries

display fib statistics

Clear IP traffic statistics

reset ip statistics

Available in user view

Clear TCP traffic statistics

reset tcp statistics

Clear UDP traffic statistics

reset udp statistics

 

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