Table of Contents

1 Static Routing Configuration· 1-1

Introduction· 1-1

Static Route· 1-1

Default Route· 1-1

Application Environment of Static Routing· 1-2

Configuring a Static Route· 1-2

Configuration Prerequisites· 1-2

Configuration Procedure· 1-2

Displaying and Maintaining Static Routes· 1-3

Static Route Configuration Example· 1-3

Basic Static Route Configuration Example· 1-3

 

When configuring a static route, go to these sections for information you are interested in:

l          Introduction

l          Configuring a Static Route

l          Displaying and Maintaining Static Routes

l          Static Route Configuration Example

 

 

Introduction

Static Route

A static route is a manually configured. If a network’s topology is simple, you only need to configure static routes for the network to work normally. The proper configuration and usage of static routes can improve network performance and ensure bandwidth for important network applications.

The disadvantage of using static routes is that they cannot adapt to network topology changes. If a fault or a topological change occurs in the network, the routes will be unreachable and the network breaks. In this case, the network administrator has to modify the static routes manually.

Default Route

If the destination address of a packet fails to match any entry in the routing table, the packet will be discarded.

After a default route is configured on a router, any packet whose destination IP address matches no entry in the routing table can be forwarded to a designated upstream router.

A router selects the default route only when it cannot find any matching entry in the routing table.

l          If the destination address of a packet fails to match any entry in the routing table, the router selects the default route to forward the packet.

l          If there is no default route and the destination address of the packet fails to match any entry in the routing table, the packet will be discarded and an ICMP packet will be sent to the source to report that the destination or the network is unreachable.

The network administrator can configure a default route with both destination and mask being 0.0.0.0. The router forwards any packet whose destination address fails to match any entry in the routing table to the next hop of the default static route.

Application Environment of Static Routing

Before configuring a static route, you need to know the following concepts:

1)        Destination address and mask

In the ip route-static command, an IPv4 address is in dotted decimal format and a mask can be either in dotted decimal format or in the form of mask length (the digits of consecutive 1s in the mask).

2)        Output interface and next hop address

While configuring a static route, you can specify either the output interface or the next hop address depending on the specific occasion. The next hop address can not be a local interface IP address; otherwise, the route configuration will not succeed.

In fact, all the route entries must have a next hop address. When forwarding a packet, a router first searches the routing table for the route to the destination address of the packet. The system can find the corresponding link layer address and forward the packet only after the next hop address is specified.

When specifying the output interface, note that:

l          If the output interface is a Null 0, there is no need to configure the next hop address.

l          If the output interface is a VLAN interface or a management Ethernet port (M-GigabitEthernet), you must specify the corresponding next hop for the output interface.

3)        Other attributes

You can configure different preferences for different static routes so that route management policies can be applied more flexibly. For example, specifying the same preference for different routes to the same destination enables load sharing, while specifying different preferences for these routes enables route backup.

Configuring a Static Route

Configuration Prerequisites

Before configuring a static route, you need to finish the following tasks:

l          Configure the physical parameters for related interfaces

l          Configure the link-layer attributes for related interfaces

l          Configure the IP addresses for related interfaces

Configuration Procedure

Follow these steps to configure a static route:

 

 

Displaying and Maintaining Static Routes

 

Static Route Configuration Example

Basic Static Route Configuration Example

Network requirements

The IP addresses and masks of the switches and hosts are shown in the following figure. Static routes are required for interconnection between any two hosts.

Figure 1-1 Network diagram for static route configuration

 

Configuration procedure

1)        Configuring IP addresses for interfaces (omitted)

2)        Configuring static routes

# Configure a default route on Switch A.

<SwitchA> system-view

[SwitchA] ip route-static 0.0.0.0 0.0.0.0 1.1.4.2

# Configure two static routes on Switch B.

<SwitchB> system-view

[SwitchB] ip route-static 1.1.2.0 255.255.255.0 1.1.4.1

[SwitchB] ip route-static 1.1.3.0 255.255.255.0 1.1.5.6

# Configure a default route on Switch C

<SwitchC> system-view

[SwitchC] ip route-static 0.0.0.0 0.0.0.0 1.1.5.5

3)        Configure the hosts.

The default gateways for the three hosts A, B and C are 1.1.2.3, 1.1.6.1 and 1.1.3.1 respectively. The configuration procedure is omitted.

4)        Display the configuration.

# Display the IP routing table of Switch A.

[SwitchA] display ip routing-table

Routing Tables: Public

         Destinations : 7       Routes : 7

 

Destination/Mask    Proto  Pre  Cost         NextHop         Interface

 

0.0.0.0/0           Static 60   0            1.1.4.2         Vlan500

1.1.2.0/24          Direct 0    0            1.1.2.3         Vlan300

1.1.2.3/32          Direct 0    0            127.0.0.1       InLoop0

1.1.4.0/30          Direct 0    0            1.1.4.1         Vlan500

1.1.4.1/32          Direct 0    0            127.0.0.1       InLoop0

127.0.0.0/8         Direct 0    0            127.0.0.1       InLoop0

127.0.0.1/32        Direct 0    0            127.0.0.1       InLoop0

# Display the IP routing table of Switch B.

[SwitchB] display ip routing-table

Routing Tables: Public

         Destinations : 10       Routes : 10

 

Destination/Mask    Proto  Pre  Cost         NextHop         Interface

 

1.1.2.0/24          Static 60   0            1.1.4.1         Vlan500

1.1.3.0/24          Static 60   0            1.1.5.6         Vlan600

1.1.4.0/30          Direct 0    0            1.1.4.2         Vlan500

1.1.4.2/32          Direct 0    0            127.0.0.1       InLoop0

1.1.5.4/30          Direct 0    0            1.1.5.5         Vlan600

1.1.5.5/32          Direct 0    0            127.0.0.1       InLoop0

127.0.0.0/8         Direct 0    0            127.0.0.1       InLoop0

127.0.0.1/32        Direct 0    0            127.0.0.1       InLoop0

1.1.6.0/24          Direct 0    0            192.168.1.47    Vlan100

1.1.6.1/32          Direct 0    0            127.0.0.1       InLoop0      

# Use the ping command on Host B to check reachability to Host A, assuming Windows XP runs on the two hosts.

C:\Documents and Settings\Administrator>ping 1.1.2.2

 

Pinging 1.1.2.2 with 32 bytes of data:

 

Reply from 1.1.2.2: bytes=32 time=1ms TTL=255

Reply from 1.1.2.2: bytes=32 time=1ms TTL=255

Reply from 1.1.2.2: bytes=32 time=1ms TTL=255

Reply from 1.1.2.2: bytes=32 time=1ms TTL=255

 

Ping statistics for 1.1.2.2:

    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

    Minimum = 1ms, Maximum = 1ms, Average = 1ms

# Use the tracert command on Host B to check reachability to Host A.

[HostB] tracert 1.1.2.2

 

Tracing route to 1.1.2.2 over a maximum of 30 hops

 

  1    <1 ms    <1 ms    <1 ms  1.1.6.1

  2    <1 ms    <1 ms    <1 ms  1.1.4.1

  3     1 ms    <1 ms    <1 ms  1.1.2.2

 

Trace complete.