H3C S5120-SI Series User manual

H3C S5120-SI Switch Series
Layer 3 - IP Routing Configuration Guide
Hangzhou H3C Technologies Co., Ltd.
http://www.h3c.com
Software version: Release 1513
Document version: 6W100-20130425

Copyright © 2013, Hangzhou H3C Technologies Co., Ltd. and its licensors
All rights reserved
No part of this manual may be reproduced or transmitted in any form or by any means without prior
written consent of Hangzhou H3C Technologies Co., Ltd.
Trademarks
H3C, , H3CS, H3CIE, H3CNE, Aolynk, , H3Care, , IRF, NetPilot, Netflow,
SecEngine, SecPath, SecCenter, SecBlade, Comware, ITCMM and HUASAN are trademarks of
Hangzhou H3C Technologies Co., Ltd.
All other trademarks that may be mentioned in this manual are the property of their respective owners
Notice
The information in this document is subject to change without notice. Every effort has been made in the
preparation of this document to ensure accuracy of the contents, but all statements, information, and
recommendations in this document do not constitute the warranty of any kind, express or implied.

Preface
The H3C S5120-SI documentation set includes 10 configuration guides, which describe the software
features for the H3C S5120-SI Switch Series Release 1513, and guide you through the software
configuration procedures. These configuration guides also provide configuration examples to help you
apply software features to different network scenarios.
The Layer 3—IP Routing Configuration Guide describes routing fundamentals and configuration.
This preface includes:
•Audience
•Added and modified features
•Conventions
•About the H3C S5120-SI documentation set
•Obtaining documentation
•Technical support
•Documentation feedback
Audience
This documentation is intended for:
•Network planners
•Field technical support and servicing engineers
•Network administrators working with the S5120-SI series
Added and modified features
None
Conventions
This section describes the conventions used in this documentation set.
Command conventions
Convention Descri
p
tion
Boldface Bold text represents commands and keywords that you enter literally as shown.
Italic Italic text represents arguments that you replace with actual values.

[ ] Square brackets enclose syntax choices (keywords or arguments) that are optional.
{ x | y | ... }
Braces enclose a set of required syntax choices separated by vertical bars, from which
you select one.
[ x | y | ... ]
Square brackets enclose a set of optional syntax choices separated by vertical bars, from
which you select one or none.
{ x | y | ... } *
Asterisk marked braces enclose a set of required syntax choices separated by vertical
bars, from which you select at least one.
[ x | y | ... ] *
Asterisk marked square brackets enclose optional syntax choices separated by vertical
bars, from which you select one choice, multiple choices, or none.
&<1-n> The argument or keyword and argument combination before the ampersand (&) sign can
be entered 1 to n times.
# A line that starts with a pound (#) sign is comments.
GUI conventions
Convention Descri
p
tion
Boldface Window names, button names, field names, and menu items are in Boldface. For
example, the New User window appears; click OK.
> Multi-level menus are separated by angle brackets. For example, File > Create > Folder.
Convention Descri
p
tion
< > Button names are inside angle brackets. For example, click <OK>.
[ ] Window names, menu items, data table and field names are inside square brackets. For
example, pop up the [New User] window.
/ Multi-level menus are separated by forward slashes. For example, [File/Create/Folder].
Symbols
Convention Descri
p
tion
WARNING An alert that calls attention to important information that if not understood or followed can
result in personal injury.
CAUTION An alert that calls attention to important information that if not understood or followed can
result in data loss, data corruption, or damage to hardware or software.
IMPORTANT An alert that calls attention to essential information.
NOTE An alert that contains additional or supplementary information.
TIP An alert that provides helpful information.
Network topology icons
Represents a generic network device, such as a router, switch, or firewall.
Represents a routing-capable device, such as a router or Layer 3 switch.

Represents a generic switch, such as a Layer 2 or Layer 3 switch, or a router that supports
Layer 2 forwarding and other Layer 2 features.
Port numbering in examples
The port numbers in this document are for illustration only and might be unavailable on your device.
About the H3C S5120-SI documentation set
The H3C S5120-SI documentation set includes:
Cate
g
or
y
Documents Pur
p
oses
Product
description and
specifications
Marketing brochures Describe product specifications and benefits.
RPS Ordering Information for H3C
Low-End Ethernet Switches
Provides the RPS and switch compatibility matrix and
RPS cable specifications.
H3C Low End Series Ethernet
Switches Pluggable Modules
Manual
Describes the models, appearances, and
specifications of the pluggable modules available for
the products.
Hardware
installation
Quick Start Guide Provides a quick guide to hardware installation.
Installation Manual
Provides a complete guide to hardware installation
and hardware specifications.
Provides regulatory information and the safety
instructions that must be followed during installation.
Pluggable SFP[SFP+][XFP]
Transceiver Modules Installation
Guide
Guides you through installing SFP/SFP+/XFP
transceiver modules.
Software
configuration
Configuration guides Describe software features and configuration
procedures.
Command references Provide a quick reference to all available commands.
Operations
and
maintenance
Release notes
Provide information about the product release,
including the version history, hardware and software
compatibility matrix, version upgrade information,
technical support information, and software
upgrading.
Obtaining documentation
You can access the most up-to-date H3C product documentation on the World Wide Web
at http://www.h3c.com.
Click the links on the top navigation bar to obtain different categories of product documentation:
[Technical Support & Documents > Technical Documents] – Provides hardware installation, software
upgrading, and software feature configuration and maintenance documentation.
[Products & Solutions] – Provides information about products and technologies, as well as solutions.

[Technical Support & Documents > Software Download] – Provides the documentation released with the
software version.
Technical support
servic[email protected]
http://www.h3c.com
Documentation feedback
You can e-mail your comments about product documentation to [email protected].
We appreciate your comments.

i
Contents
IP routing basics ··························································································································································· 1
IP routing overview ···························································································································································1
Routing·······································································································································································1
Routing table and FIB table ·····································································································································1
Routing protocol overview················································································································································3
Static routing and dynamic routing ························································································································3
Routing protocols and routing preference ·············································································································3
Displaying and maintaining a routing table ··················································································································4
Static routing configuration ········································································································································· 6
Introduction ········································································································································································6
Static route ································································································································································6
Default route······························································································································································6
Static route configuration items·······························································································································6
Configuring a static route·················································································································································7
Configuration prerequisites ·····································································································································7
Configuration procedure ·········································································································································7
Displaying and maintaining static routes ·······················································································································8
Static route configuration examples································································································································8
Basic static route configuration example ···············································································································8
IPv6 static routing configuration································································································································11
Introduction to IPv6 static routing ································································································································· 11
IPv6 static route features······································································································································· 11
Default IPv6 route ·················································································································································· 11
Configuring an IPv6 static route ··································································································································· 11
Configuration prerequisites ·································································································································· 11
Configuration procedure ······································································································································ 12
Displaying and maintaining IPv6 static routes············································································································ 12
IPv6 static routing configuration example ··················································································································· 12
Index ···········································································································································································15

1
IP routing basics
NOTE:
The term
router in this document refers to a routing-capable device.
IP routing overview
Routing
Routing in the Internet is achieved through routers. Upon receiving a packet, a router determines the
optimal path based on the destination address and forwards the packet to the next router in the path.
When the packet reaches the last router, it then forwards the packet to the intended destination host.
Routing provides the path information that guides the forwarding of packets.
Routing table and FIB table
The routing table plays a key role in route selection and the forwarding information base (FIB) table plays
a key role in packet forwarding. Each router maintains a routing table and a FIB table.
Routes in a routing table can be divided into the following categories by origin:
•Direct routes—Routes discovered by data link protocols, also known as "interface routes"
•Static routes—Routes that are manually configured
•Dynamic routes—Routes that are discovered dynamically by routing protocols
Each entry in the FIB table specifies a physical interface that packets destined for a certain address
should go out to reach the next hop—the next router—or the directly connected destination.
Introduction to routing table
Each router maintains a local routing table, and each routing protocol maintains a protocol routing table.
•Routing table of a protocol
A protocol routing table stores routes discovered by the routing protocol.
•Local routing table
A local routing table stores the routes found by all protocols and delivers the optimal routes to the FIB
table to guide packet forwarding. The optimal route selection is based on the routing protocol
preferences and route metrics.

2
Contents of a routing table
A route entry includes the following key items:
•Destination address—Destination IP address or destination network
•Network mask—Specifies, in company with the destination address, the address of the destination
network. A logical AND operation between the destination address and the network mask yields
the address of the destination network. For example, if the destination address is 129.102.8.10 and
the mask 255.255.0.0, the address of the destination network is 129.102.0.0. A network mask is
made up of a certain number of consecutive 1s. It can be expressed in dotted decimal format or by
the number of the 1s.
•Outbound interface—Specifies the interface through which a matching IP packet is to be
forwarded.
•Next hop—Specifies the IP address of the next-hop router on the path. If only the outbound interface
is specified, its IP address will be the IP address of the next hop.
•Preference for the route—Routes to the same destination but having different next hops may have
different priorities and be found by various routing protocols or manually configured. The optimal
route is the one with the highest preference (with the smallest metric).
Routes can be divided into the following categories by destination:
•Subnet route—The destination is a subnet.
•Host route—The destination is a host.
Based on whether the destination is directly connected to the router, routes can be divided into:
•Direct routes—The destination is directly connected to the router.
•Indirect routes—The destination is not directly connected to the router.
To prevent the routing table from getting too large, configure a default route. Packets not matching any
specific entries in the routing table will be forwarded through the default route.
In Figure 1, Router A is connected to three networks. Its routing table is shown under the network
topology.

3
Figure 1 A sample routing table
Destination Network Nexthop
Interface
11.1.1.0 1.1.1.2 Vlan1
12.1.1.0 2.2.2.1
Vlan2
13.1.1.0 3.3.3.1
Vlan3
Routing protocol overview
Static routing and dynamic routing
Static routing is easy to configure and requires less system resources. It works well in small, stable
networks with simple topologies. Its major drawback is that you must perform routing configuration
again whenever the network topology changes; it cannot adjust to network changes by itself.
Based on dynamic routing protocols, dynamic routing can detect network topology changes and
recalculate the routes, so it is suitable for large networks. However, dynamic routing is difficult to
configure. It not only imposes higher requirements on the system, but also consumes a certain amount of
network resources.
Routing protocols and routing preference
Different routing protocols may find different routes to the same destination. However, not all of those
routes are optimal. In fact, at a particular moment, only one protocol can uniquely determine the current
optimal route to the destination. For route selection, each routing protocol—including static routes—is
assigned a preference. The route found by the routing protocol with the highest preference is preferred.
11.1.1.0/24
13.1.1.0/2412.1.1.0/24
Router A
Router B
Router C Router D
Vlan1
1.1.1.1/24
Vlan2
2.2.2.2/24 Vlan3
3.3.3.3/24
1.1.1.2/24
2.2.2.1/24 3.3.3.1/24