When configuring a static route, go to
these sections for information you are interested in:
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Introduction
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Configuring
a Static Route
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Application
Environment of Static Routing
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Displaying
and Maintaining Static Routes
l
Configuration
Example
The term
“router” in this document refers to a router in a generic sense or
a Layer 3 switch.
1.1 Introduction
A static route is a special route that is
manually configured by the network administrator. 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.
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
create the default route with both destination and mask being 0.0.0.0, and some
dynamic routing protocols, such as OSPF, RIP and IS-IS, can also generate the
default route.
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 take effect.
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:
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If the output interface is a NULL 0 interface,
there is no need to configure the next hop address.
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You are not recommended to specify a broadcast
interface (such as VLAN interface) as the output interface, because a broadcast
interface may have multiple next hops. If you have to do so, 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.
1.2 Configuring a Static Route
Before configuring a static route, you need
to configure the IP addresses for related interfaces.
Follow these steps to configure a static
route:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
—
|
|
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 ] [ tag tag-value ]
[ description description-text ]
|
Required
By default, preference for static
routes is 60, tag is 0, and no description information is configured.
|
|
Configure the default preference for
static routes
|
ip route-static default-preference default-preference-value
|
Optional
60 by default
|
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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, such as a VLAN interface.
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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.
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You can flexibly control static routes by
configuring tag values and using the tag values in the routing policy.
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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.
1.3 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.
If you specify the nexthop but not outgoing
interface when configuring a static route, you can associate the static route
with a track entry to check the static route validity:
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When the track entry is positive, the static
route's nexthop is reachable and the static route takes effect.
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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.
I. 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.
Follow these steps to detect the
reachability of a static route's nexthop through Track:
|
To do…
|
Use the command…
|
Remarks
|
|
Enter system view
|
system-view
|
—
|
|
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 ] [ tag tag-value ] [
description description-text ]
|
Required
Not configured by default
|
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To configure this feature for an existing static
route, simply associate the static route with a track entry. For a non-existent
static route, configure it and associate it with a Track entry.
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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.
|
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
|
|
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
|
1.5 Configuration Example
I. 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.
II. Network diagram
Figure
1-1 Network diagram for static route configuration
III. 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 result
# 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
1.1.5.0/30 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
# From Host A, use the ping command
to verify the network layer reachability to Host B and Host C.
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The term “router” in this document
refers to a router in a generic sense or a Layer 3 switch.
l
The S5500-EI series only support single RIP
process.
When configuring RIP, go to these sections
for information you are interested in:
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RIP Overview
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Configuring RIP Basic Functions
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Configuring RIP Route Control
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Configuring RIP Network
Optimization
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Displaying and Maintaining
RIP
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RIP Configuration Examples
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Troubleshooting RIP
2.1 RIP Overview
RIP is a simple Interior Gateway Protocol
(IGP), mainly used in small-sized networks, such as academic networks and
simple LANs. RIP is not applicable to complex networks.
RIP is still widely used in practical
networking due to easier implementation, configuration and maintenance than
OSPF and IS-IS.
I. Basic concepts
RIP is a distance vector routing protocol,
using UDP packets for exchanging information through port 520.
RIP uses a hop count to measure the
distance to a destination. The hop count is known as the metric. The hop count
from a router to a directly connected network is 0. The hop count from one
router to a directly connected router is 1. To limit convergence time, the
range of RIP metric value is from 0 to 15. A metric value of 16 (or bigger) is
considered infinite, which means the destination network is unreachable. That
is why RIP is not suitable for large-scaled networks.
RIP prevents
routing loops by implementing the split horizon and poison reverse functions.
II. RIP routing table
A RIP router
has a routing table containing routing entries of all reachable destinations,
and each routing entry contains:
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Destination address: IP address of a host or a
network.
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Next hop: IP address of the adjacent
router’s interface to reach the destination.
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Egress interface: Packet outgoing interface.
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Metric: Cost from the local router to the
destination.
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Route time: Time elapsed since the routing entry
was last updated. The time is reset to 0 every time the routing entry is
updated.
l &nb
