H3C S5120-EI Series User manual

H3C S5120-EI Series Ethernet Switches
Layer 3 IP Routing Configuration Guide
Hangzhou H3C Technologies Co., Ltd.
http://www.h3c.com

Copyright © 2003-2010, 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.
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Preface
The H3C S5120-EI documentation set includes 13 configuration guides, which describe the software
features for the H3C S5120-EI Series Ethernet Switches 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.
This preface includes:
•Audience
•Conventions
•About the H3C S5120-EI Documentation Set
•Obtaining Documentation
•Documentation Feedback
Audience
This documentation is intended for:
Network planners
Field technical support and servicing engineers
Network administrators working with the S5120-EI series

4
Conventions
This section describes the conventions used in this documentation set.
Command conventions
Con
v
ention 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 may select 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
< > 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
Means reader be extremely careful. Improper operation may cause bodily
injury.
Means reader be careful. Improper operation may cause data loss or damage
to equipment.
Means an action or information that needs special attention to ensure successful
configuration or good performance.
Means a complementary description.
Means techniques helpful for you to make configuration with ease.

5
Network topology icons
Convention Descri
p
tion
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.

6
About the H3C S5120-EI documentation set
Cate
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or
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Guides you through installing and remodeling H3C
cabinets.
H3C Pluggable SFP
[SFP+][XFP] Transceiver
Modules Installation
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Guides you through installing SFP/SFP+/XFP
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Adjustable Slider Rail
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Guides you through installing adjustable slider rails to
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upgrading.
Error code reference Explains the error codes.

7
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
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[Technical Support & Documents > Software Download] – Provides the documentation released with the
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Documentation feedback
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We appreciate your comments.

8
Table of Contents
Preface ·········································································································································································· 3
Audience············································································································································································3
Conventions ·······································································································································································4
About the H3C S5120-EI documentation set ·················································································································6
IP routing overview······················································································································································· 9
Routing ···············································································································································································9
Routing table and FIB table ·····································································································································9
Routing protocol overview············································································································································· 11
Static routing and dynamic routing ····················································································································· 11
Routing protocols and routing priority ················································································································ 11
Displaying and maintaining a routing table ··············································································································· 12
Static routing configuration ·······································································································································14
Introduction ····································································································································································· 14
Static route ····························································································································································· 14
Default route··························································································································································· 14
Application environment of static routing ··········································································································· 14
Configuring a static route·············································································································································· 15
Configuration prerequisites ·································································································································· 15
Configuration procedure ······································································································································ 15
Detecting reachability of the static route’s nexthop···································································································· 16
Detecting nexthop reachability through track ···································································································· 16
Displaying and maintaining static routes ···················································································································· 16
Static route configuration example ······························································································································ 17
Basic static route configuration example ············································································································ 17
IPv6 static routing configuration································································································································20
Introduction to IPv6 static routing ································································································································· 20
Features of IPv6 static routes ································································································································ 20
Default IPv6 route ·················································································································································· 20
Configuring an IPv6 static route ··································································································································· 20
Configuration prerequisites ·································································································································· 20
Configuring an IPv6 static route ·························································································································· 20
Displaying and maintaining IPv6 static routes············································································································ 21
IPv6 static routing configuration example ··················································································································· 21
Obtaining support for your product··························································································································24
Register your product····················································································································································· 24
Purchase value-added services····································································································································· 24
Troubleshoot online························································································································································ 24
Access software downloads·········································································································································· 25
Telephone technical support and repair······················································································································ 25
Contact us ······································································································································································· 25
Acronyms····································································································································································26
Index ···········································································································································································42

9
IP routing overview
Routing
Routers are responsible for forwarding data packets along networks. Upon receiving a packet, a router
determines the optimal path based on the destination address. When the packet reaches the last router in
the path, it then forwards the packet to the intended destination host.
Routing provides the path information for guiding the forwarded packets.
The term router in this document refers to a router in a generic sense or a Layer 3 switch.
Routing table and FIB table
Routing table
The routing table plays a key role in route selection while the 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.
Dynamic routing protocol is not supported on the S5120-EI Series Ethernet Switches.
Each entry in the FIB table specifies the physical interface to which a packet should travel: the next hop
(the next router), or directly to its intended destination.
Introduction to routing table
Each router maintains a local routing table, and each routing protocol maintains a protocol routing table.
•Protocol routing table:
A protocol routing table stores routes discovered by the routing protocol.
A routing protocol can redistribute and advertise routes generated by other protocols. For example,
OSPF can redistribute direct routes, static routes, and IS-IS routes to the OSPF routing table, and then
advertise those routes.
•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.

10
Contents of a routing table
A routing table 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
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 the IP packets are to be forwarded.
•IP address of the next hop: Specifies the address of the next router on the path. If only the outbound
interface is configured, its address will be the IP address of the next hop.
•Priority for the route: Routes to the same destination but having different nexthops may have different
priorities and be found by various routing protocols or manually configured. The optimal route is the
one with the highest priority (with the smallest metric).
Routes can be divided into two categories by destination:
•Subnet routes: The destination is a subnet.
•Host routes: The destination is a host.
Based on whether the destination is directly connected to a given 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, you can configure a default route. All packets without
matching any entry in the routing table will be forwarded through the default route.
In Figure 1, the IP address on each cloud represents the address of the network. Router G is connected to
three networks and therefore has three IP addresses for its three physical interfaces. Its routing table is
shown under the network topology.
Figure 1 A sample routing table

11
Router A
Router B
Router H
Router E
16.0.0.2
17.0.0.3
15.0.0.0 12.0.0.0
17.0.0.0
11.0.0.016.0.0.0
13.0.0.0
14.0.0.0
Router C
Router D
Router F
Router G
11.0.0.1
12.0.0.1
12.0.0.2
15.0.0.1
15.0.0.2
17.0.0.1
16.0.0.1
13.0.0.1
13.0.0.2
14.0.0.1
14.0.0.2
14.0.0.3
14.0.0.4
17.0.0.2
11.0.0.2
13.0.0.3
Destination Network Nexthop Interface
11.0.0.0 11.0.0.1 2
12.0.0.0 12.0.0.1 1
13.0.0.0 12.0.0.2 1
14.0.0.0 14.0.0.4 3
15.0.0.0 14.0.0.2 3
16.0.0.0 14.0.0.2 3
17.0.0.0 11.0.0.2 2
Routing protocol overview
Static routing and dynamic routing
Static routing is easier to configure and requires fewer system resources. It works well in small, stable
networks with simple topologies. Its major drawback is that you must reconfigure it whenever the network
topology changes; it cannot self-adjust to network changes.
Dynamic routing is based on dynamic routing protocols, which can detect network topology changes and
recalculate the routes accordingly; therefore, dynamic routing is suitable for large networks. Its
disadvantages are that it is difficult to configure, imposes higher requirements on the system, and
consumes network resources.
Routing protocols and routing priority
Different routing protocols may find different routes to the same destination. However, not all of those
routes are optimal. At a particular moment, only one protocol can uniquely determine the current optimal
route to the destination. For the purpose of route selection, each routing protocol (including static routes) is
assigned a priority. The route found by the routing protocol with the highest priority is preferred.

12
The following table lists some routing protocols and the default priorities for routes found by them:
Routing approach Priority
DIRECT 0
STATIC 60
UNKNOWN 256
•The smaller the priority value, the higher the priority.
•The priority for a direct route is always 0, which you cannot change. Any other type of routes can have their
priorities manually configured.
•Each static route can be configured with a different priority.
•IPv4 and IPv6 routes have their own respective routing tables.
Displaying and maintaining a routing table
To do… Use the command… Remarks
Display brief information about the
active routes in the routing table
display ip routing-table [ verbose || { begin
|exclude |include } regular-expression ]
Available in
any view
Display information about routes to the
specified destination
display ip routing-table ip-address [ mask-length
| mask ] [ longer-match ] [ verbose ]
Available in
any view
Display information about routes with
destination addresses in the specified
range
display ip routing-table ip-address1 { mask-
length | mask } ip-address2 { mask-length | mask } [
verbose ]
Available in
any view
Display routes of a routing protocol display ip routing-table protocol protocol [
inactive | verbose ]
Available in
any view
Display statistics about the network
routing table display ip routing-table statistics Available in any view
Clear statistics for the routing table reset ip routing-table statistics protocol {all
|protocol }
Available in
user view
Display brief IPv6 routing table
information display ipv6 routing-table Available in any view
Display verbose IPv6 routing table
information display ipv6 routing-table verbose Available in any view
Display routing information for a
specified destination IPv6 address
display ipv6 routing-table ipv6-address prefix-
length [ longer-match ] [ verbose ]
Available in
any view
Display IPv6 routing information of a
routing protocol
display ipv6 routing-table protocol protocol [
inactive | verbose ]
Available in
any view
Display IPv6 routing statistics display ipv6 routing-table statistics Available in
any view
Display IPv6 routing information for an
IPv6 address range
display ipv6 routing-table ipv6-address1 prefix-
length1 ipv6-address2 prefix-length2 [ verbose ]
Available in
any view
Clear specified IPv6 routing table reset ipv6 routing-table statistics protocol { Available in

13
To do… Use the command… Remarks
statistics all | protocol } user view

14
Static routing configuration
Introduction
Static route
A static route is manually configured, but if a network’s topology is simple, you only need to configure
static routes for the network to function. 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
the event of a fault or topological change, the network administrator has to modify the static routes
manually.
The term router in this document refers to a router in a generic sense or a Layer 3 switch.
Default route
If the packet’s destination address fails to match any entry in the routing table, the packet is 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.
•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.
•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.
You can configure a default route with both the 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:
•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 number of consecutive 1s in the
mask).
•Output interface and next hop address:

15
While configuring a static route, you can specify either the output interface or the next hop address
depending on the specific occasion. For a NULL0 interface, if the output interface has already been
configured, there is no need to configure the next hop address
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. The next hop address can not be a local interface IP address; otherwise, the route
configuration will not take effect.
•Other attributes:
You can configure different preferences for different static routes so that route management policies
can be applied more flexibly.
Configuring a static route
Configuration prerequisites
Before configuring a static route, complete the following tasks:
•Configure the physical parameters for related interfaces
•Configure the link-layer attributes for related interfaces
•Configure the IP addresses for related interfaces
Configuration procedure
Follow these steps to configure a static route:
To do… Use the command… Remarks
1. Enter system view system-view —
2. Configure a static
route
ip route-static dest-address { mask | mask-
length } { next-hop-address |interface-type
interface-number [ next-hop-address ] } [
preference preference-value ] [ description
description-text ]
Required
By default, preference for static
routes is 60 and no description
information is configured.
3. Configure the
default preference
for static routes
ip route-static default-preference
default-preference-value
Optional
60 by default
•When configuring a static route, the static route does not take effect if you specify the next hop address first and
then configure it as the IP address of a local interface.
•If you do not specify the preference when configuring a static route, the default preference will be used.
Reconfiguring the default preference applies only to newly created static routes.
•If the destination IP address and mask are both configured as 0.0.0.0 with the ip route-static command, the
route is the default route.

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Detecting reachability of the static route’s nexthop
If a static route fails due to a topology change or a fault, the connection will be interrupted. To improve
network stability, the system needs to detect reachability of the static route’s next hop and switch to a
backup route once the next hop is unreachable.
Following method can be used to detect reachability of the static route’s next hop.
Detecting nexthop reachability through track
If you specify the nexthop, but not the outgoing interface when configuring a static route, you can
associate the static route with a track entry to check the static route validity:
•When the track entry is positive, the static route's nexthop is reachable and the static route takes
effect.
•When the track entry is negative, the static route's nexthop is unreachable and the static route is
invalid. For details about track, refer to Track Configuration in the High Availability Configuration
Guide.
Network requirements
To detect the reachability of a static route's nexthop through a Track entry, you need to create a Track
first. For detailed Track configuration procedure, refer to Track Configuration in the High Availability
Configuration Guide.
Configuration procedure
Follow these steps to detect the reachability of a static route's nexthop through Track:
To do… Use the command… Remarks
1. Enter system view system-view —
2. Associate the static
route with a track entry
ip route-static dest-address {mask | mask-length }next-
hop-address track track-entry-number [ preference
preference-value ] [ description description-text ]
Required
Not configured
by default
•To configure this feature for an existing static route, associate the static route with a track entry. For a non-existent
static route, configure it and associate it with a Track entry.
•If a static route needs route recursion, the associated track entry must monitor the nexthop of the recursive route
instead of that of the static route; otherwise, a valid route may be mistakenly considered invalid.
Displaying and maintaining static routes
To do… Use the command… Remarks
Display the current configuration information display current-configuration
Available in
any view
Display the brief information of the IP routing
table display ip routing-table
Display the detailed information of the IP
routing table display ip routing-table verbose

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To do… Use the command… Remarks
View information of static routes display ip routing-table protocol static
[ inactive | verbose ]
Delete all the static routes delete static-routes all Available In
system view
Static route configuration example
Basic static route configuration example
Network requirements
The IP addresses and masks of the switches and hosts are shown in Figure 2. Static routes are required for
interconnection between any two hosts.
Figure 2 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

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[SwitchC] ip route-static 0.0.0.0 0.0.0.0 1.1.5.5
3. Configure the hosts.
The default gateways for 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 1.1.6.1 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

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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.

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IPv6 static routing configuration
Introduction to IPv6 static routing
A static route is manually configured and works well in simple networks. Proper configuration and use
can improve network performance and ensure enough bandwidth for high priority applications.
Unfortunately, static routes also have shortcomings. Any topology changes require manual configuration
and modification to the corresponding static routes.
The term router in this document refers to either a router in a generic sense or a Layer 3 switch running routing
protocols.
Features of IPv6 static routes
Similar to IPv4 static routes, IPv6 static routes work well in simple IPv6 network environments.
The major difference between these two resides in the destination and next hop addresses. IPv6 static
routes use IPv6 addresses whereas IPv4 static routes use IPv4 addresses.
Default IPv6 route
An IPv6 static route with a destination prefix of ::/0 is a default IPv6 route. The default route is used to
forward packets that match no specific routes in the routing table.
Configuring an IPv6 static route
In small IPv6 networks, IPv6 static routes can be used to forward packets. In comparison to dynamic
routes, it helps to save network bandwidth.
Configuration prerequisites
•Configuring parameters for the related interfaces
•Configuring link layer attributes for the related interfaces
•Enabling IPv6 packet forwarding
•Ensuring that the neighboring nodes are IPv6 reachable
Configuring an IPv6 static route
To do… Use the commands… Remarks
1. Enter system view system-view —
2. Configure an IPv6
static route
ipv6 route-static ipv6-address prefix-length [
interface-type interface-number ] nexthop-address [
Required
The default preference of