Login
- Table of Contents
-
- 06-Layer 3 - IP Routing Configuration Guides
- 00-Preface
- 01-Basic IP routing configuration
- 02-Static routing configuration
- 03-RIP configuration
- 04-OSPF configuration
- 05-IS-IS configuration
- 06-BGP configuration
- 07-Policy-based routing configuration
- 08-IPv6 static routing configuration
- 09-RIPng configuration
- 10-OSPFv3 configuration
- 11-IPv6 policy-based routing configuration
- 12-Routing policy configuration
- 13-DCN configuration
- 14-Dual-stack PBR configuration
- Related Documents
-
| Title | Size | Download |
|---|---|---|
| 02-Static routing configuration | 223.05 KB |
Configuring a static route group
Configuring floating static routes
Configuring BFD for static routes
Configuring BFD control packet mode
Configuring BFD echo packet mode
Configuration restrictions and guidelines
Configuring static route FRR by specifying a backup next hop
Configuring static route FRR to automatically select a backup next hop
Enabling BFD echo packet mode for static route FRR
Displaying and maintaining static routes
Static route configuration examples
Basic static route configuration example
BFD for static routes configuration example (direct next hop)
BFD for static routes configuration example (indirect next hop)
Static route FRR configuration example
Configuring static routing
Static routes are manually configured. If a network's topology is simple, you only need to configure static routes for the network to work correctly.
Static routes cannot adapt to network topology changes. If a fault or a topological change occurs in the network, the network administrator must modify the static routes manually.
Configuring a static route
Before you configure 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.
You can associate Track with a static route to monitor the reachability of the next hops. For more information about Track, see High Availability Configuration Guide.
If you configure only VPN instance settings without specifying a next hop for a static route, you must also configure service loopback group settings for the static route to take effect.
To configure service loopback group settings for a static route:
1. Create a service loopback group of the inter-VPN forwarding service type.
2. Add any Layer 2 Ethernet interface to the service loopback group. To ensure that the static route can correctly guide traffic forwarding, do not add the Layer 2 Ethernet interfaces on the following cards to the service loopback group:
¡ SF interface modules.
¡ EC interface modules.
¡ SA interface modules.
¡ SC interface modules.
For more information about service loopback group configuration, see Layer 2—LAN Switching Configuration Guide.
To configure a static route:
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Configure a static route. |
· Method 1: · Method 2: |
By default, no static route is configured. The recursive-lookup host-route and recursive-lookup keywords are mutually exclusive. If you specify a destination VPN instance without specifying a next hop address, the destination VPN instance cannot be the same as the source VPN instance. |
|
3. (Optional.) Enable periodic sending of ARP requests to the next hops of static routes. |
ip route-static arp-request interval interval |
By default, the device does not send ARP requests to the next hops of static routes. |
|
4. (Optional.) Configure the default preference for static routes. |
ip route-static default-preference default-preference |
The default setting is 60. |
|
5. (Optional.) Delete all static routes, including the default route. |
delete [ vpn-instance vpn-instance-name ] static-routes all |
To delete one static route, use the undo ip route-static command. |
Configuring a static route group
This task allows you to batch create static routes with different prefixes but the same output interface and next hop.
You can associate Track with a static route to monitor the reachability of the next hops. For more information about Track, see High Availability Configuration Guide.
If you configure only VPN instance settings without specifying a next hop for a static route, you must also configure service loopback group settings for the static route to take effect.
To configure service loopback group settings for a static route:
1. Create a service loopback group of the inter-VPN forwarding service type.
2. Add any Layer 2 Ethernet interface to the service loopback group. To ensure that the static route can correctly guide traffic forwarding, do not add the Layer 2 Ethernet interfaces on the following cards to the service loopback group:
¡ SF interface modules.
¡ EC interface modules.
¡ SA interface modules.
¡ SC interface modules.
For more information about service loopback group configuration, see Layer 2—LAN Switching Configuration Guide.
To configure a static route group:
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Create a static route group and enter its view. |
ip route-static-group group-name |
By default, no static route group is configured. |
|
3. Add a static route prefix to the static route group. |
prefix dest-address { mask-length | mask } |
By default, no static route prefix is added to the static route group. |
|
4. (Optional.) Return to system view. |
quit |
N/A |
|
5. Configure a static route. |
· Method 1: · Method 2: |
By default, no static route is configured. The recursive-lookup host-route and recursive-lookup keywords are mutually exclusive. If you specify a destination VPN instance without specifying a next hop address, the destination VPN instance cannot be the same as the source VPN instance. |
|
6. (Optional.) Enable periodic sending of ARP requests to the next hops of static routes. |
ip route-static arp-request interval interval |
By default, the device does not send ARP requests to the next hops of static routes. |
|
7. (Optional.) Configure the default preference for static routes. |
ip route-static default-preference default-preference |
The default setting is 60. |
|
8. (Optional.) Delete all static routes, including the default route. |
delete [ vpn-instance vpn-instance-name ] static-routes all |
To delete one static route, use the undo ip route-static command. |
Configuring floating static routes
Perform this task to configure route backup to improve network reliability.
When a static or dynamic route to a destination address already exists on the device, you configure another static route with a lower priority as the backup route to improve the network reliability. This backup static route is called a floating static route and is activated only when the primary route fails. After the primary route recovers from failure, the floating static route becomes inactive and data forwarding switches back to the primary route.
A floating static route can be configured in either of the following ways
· Configure different priorities for multiple static routes to the same destination address. The route with the lower priority automatically becomes the floating static route.
· When a route to a destination address already exists on the device, configure a static route with a lower priority to the same destination address.
When you configure a floating static route, the priority value of the route must be larger than then priority value of the primary route. For more information, see "Configuring a static route."
Configuring BFD for static routes
|
|
IMPORTANT: Enabling BFD for a flapping route could worsen the situation. |
BFD provides a general-purpose, standard, medium-, and protocol-independent fast failure detection mechanism. It can uniformly and quickly detect the failures of the bidirectional forwarding paths between two routers for protocols, such as routing protocols and MPLS.
For more information about BFD, see High Availability Configuration Guide.
Configuring BFD control packet mode
This mode uses BFD control packets to detect the status of a link bidirectionally at a millisecond level.
BFD control packet mode can be applied to static routes with a direct next hop or with an indirect next hop.
If you use BFD control packet mode at the local end, you must use this mode also at the peer end.
To configure BFD control packet mode for a static route (direct next hop):
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Configure BFD control packet mode for a static route. |
· Method 1: · Method 2: |
By default, BFD control packet mode for a static route is not configured. |
To configure BFD control packet mode for a static route (indirect next hop):
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Configure BFD control packet mode for a static route. |
· Method 1: · Method 2: |
By default, BFD control packet mode for a static route is not configured. |
Configuring BFD echo packet mode
With BFD echo packet mode enabled for a static route, the output interface sends BFD echo packets to the destination device, which loops the packets back to test the link reachability.
You do not need to configure BFD echo packet mode at the peer end.
Do not use BFD for a static route with the output interface in spoofing state.
To configure BFD echo packet mode for a static route:
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Configure the source address of echo packets. |
bfd echo-source-ip ip-address |
By default, the source address of echo packets is not configured. For more information about this command, see High Availability Command Reference. |
|
3. Configure BFD echo packet mode for a static route. |
· Method 1: · Method 2: |
By default, BFD echo packet mode for a static route is not configured. |
Configuring static route FRR
A link or router failure on a path can cause packet loss. Static route fast reroute (FRR) enables fast rerouting to minimize the impact of link or node failures.
As shown in Figure 1, upon a link failure, packets are directed to the backup next hop to avoid traffic interruption. You can either specify a backup next hop for FRR or enable FRR to automatically select a backup next hop (which must be configured in advance).
Configuration restrictions and guidelines
When you configure static route FRR, follow these restrictions and guidelines:
· Do not use static route FRR and BFD (for a static route) at the same time.
· Static route does not take effect when the backup output interface is unavailable.
· Equal-cost routes do not support static route FRR.
· The backup output interface and next hop must be different from the primary output interface and next hop.
· To change the backup output interface or next hop, you must first remove the current setting.
· Besides the configured static route for FRR, the device must have another route to reach the destination.
When the state of the primary link (with Layer 3 interfaces staying up) changes from bidirectional to unidirectional or down, static route FRR quickly redirects traffic to the backup next hop. When the Layer 3 interfaces of the primary link are down, static route FRR temporarily redirects traffic to the backup next hop. In addition, the device searches for another route to reach the destination and redirects traffic to the new path if a route is found. If no route is found, traffic interruption occurs.
Configuring static route FRR by specifying a backup next hop
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Configure static route FRR. |
· Method 1: · Method 2: |
By default, static route FRR is disabled. |
Configuring static route FRR to automatically select a backup next hop
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Configure static route FRR to automatically select a backup next hop. |
ip route-static fast-reroute auto |
By default, static route FRR is disabled from automatically selecting a backup next hop. |
Enabling BFD echo packet mode for static route FRR
By default, static route FRR uses ARP to detect primary link failures. Perform this task to enable static route FRR to use BFD echo packet mode for fast failure detection on the primary link.
To enable BFD echo packet mode for static route FRR:
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Configure the source IP address of BFD echo packets. |
bfd echo-source-ip ip-address |
By default, the source IP address of BFD echo packets is not configured. The source IP address cannot be on the same network segment as any local interface's IP address. For more information about this command, see High Availability Command Reference. |
|
3. Enable BFD echo packet mode for static route FRR. |
ip route-static primary-path-detect bfd echo |
By default, BFD echo packet mode for static route FRR is disabled. |
Displaying and maintaining static routes
Execute display commands in any view.
|
Task |
Command |
|
Display static route information. |
display ip routing-table protocol static [ inactive | verbose ] |
|
Display static route next hop information. |
display route-static nib [ nib-id ] [ verbose ] |
|
Display static routing table information. |
display route-static routing-table [ vpn-instance vpn-instance-name ] [ ip-address { mask-length | mask } ] |
Static route configuration examples
Basic static route configuration example
Network requirements
As shown in Figure 2, configure static routes on the switches for interconnections between any two hosts.
Configuration procedure
1. Configure IP addresses for interfaces. (Details not shown.)
2. Configure 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
Verifying the configuration
# Display static routes on Switch A.
[SwitchA] display ip routing-table protocol static
Summary count : 1
Static Routing table status : <Active>
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
0.0.0.0/0 Static 60 0 1.1.4.2 Vlan500
Static Routing table status : <Inactive>
Summary count : 0
# Display static routes on Switch B.
[SwitchB] display ip routing-table protocol static
Summary count : 2
Static Routing table status : <Active>
Summary count : 2
Destination/Mask Proto Pre Cost NextHop Interface
1.1.2.0/24 Static 60 0 1.1.4.1 Vlan500
Static Routing table status : <Inactive>
Summary count : 0
# Use the ping command on Host B to test the reachability of Host A (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=126
Reply from 1.1.2.2: bytes=32 time=1ms TTL=126
Reply from 1.1.2.2: bytes=32 time=1ms TTL=126
Reply from 1.1.2.2: bytes=32 time=1ms TTL=126
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 test the reachability of Host A.
C:\Documents and Settings\Administrator>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.
BFD for static routes configuration example (direct next hop)
Network requirements
Configure the following, as shown in Figure 3:
· Configure a static route to subnet 120.1.1.0/24 on Switch A.
· Configure a static route to subnet 121.1.1.0/24 on Switch B.
· Enable BFD for both routes.
· Configure a static route to subnet 120.1.1.0/24 and a static route to subnet 121.1.1.0/24 on Switch C.
When the link between Switch A and Switch B through the Layer 2 switch fails, BFD can detect the failure immediately. Switch A then communicates with Switch B through Switch C.
Figure 3 Network diagram
Table 1 Interface and IP address assignment
|
Device |
Interface |
IP address |
|
Switch A |
VLAN-interface 10 |
12.1.1.1/24 |
|
Switch A |
VLAN-interface 11 |
10.1.1.102/24 |
|
Switch B |
VLAN-interface 10 |
12.1.1.2/24 |
|
Switch B |
VLAN-interface 13 |
13.1.1.1/24 |
|
Switch C |
VLAN-interface 11 |
10.1.1.100/24 |
|
Switch C |
VLAN-interface 13 |
13.1.1.2/24 |
Configuration procedure
1. Configure IP addresses for the interfaces. (Details not shown.)
2. Configure static routes and BFD:
# Configure static routes on Switch A and enable BFD control packet mode for the static route that traverses the Layer 2 switch.
<SwitchA> system-view
[SwitchA] interface vlan-interface 10
[SwitchA-vlan-interface10] bfd min-transmit-interval 500
[SwitchA-vlan-interface10] bfd min-receive-interval 500
[SwitchA-vlan-interface10] bfd detect-multiplier 9
[SwitchA-vlan-interface10] quit
[SwitchA] ip route-static 120.1.1.0 24 vlan-interface 10 12.1.1.2 bfd control-packet
[SwitchA] ip route-static 120.1.1.0 24 vlan-interface 11 10.1.1.100 preference 65
[SwitchA] quit
# Configure static routes on Switch B and enable BFD control packet mode for the static route that traverses the Layer 2 switch.
<SwitchB> system-view
[SwitchB] interface vlan-interface 10
[SwitchB-vlan-interface10] bfd min-transmit-interval 500
[SwitchB-vlan-interface10] bfd min-receive-interval 500
[SwitchB-vlan-interface10] bfd detect-multiplier 9
[SwitchB-vlan-interface10] quit
[SwitchB] ip route-static 121.1.1.0 24 vlan-interface 10 12.1.1.1 bfd control-packet
[SwitchB] ip route-static 121.1.1.0 24 vlan-interface 13 13.1.1.2 preference 65
[SwitchB] quit
# Configure static routes on Switch C.
<SwitchC> system-view
[SwitchC] ip route-static 120.1.1.0 24 13.1.1.1
[SwitchC] ip route-static 121.1.1.0 24 10.1.1.102
Verifying the configuration
# Display BFD sessions on Switch A.
<SwitchA> display bfd session
Total Session Num: 1 Up Session Num: 1 Init Mode: Active
IPv4 session working in control packet mode:
LD/RD SourceAddr DestAddr State Holdtime Interface
4/7 12.1.1.1 12.1.1.2 Up 2000ms Vlan10
The output shows that the BFD session has been created.
# Display the static routes on Switch A.
<SwitchA> display ip routing-table protocol static
Summary count : 1
Static Routing table status : <Active>
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
120.1.1.0/24 Static 60 0 12.1.1.2 Vlan10
Static Routing table status : <Inactive>
Summary count : 0
The output shows that Switch A communicates with Switch B through VLAN-interface 10. Then the link over VLAN-interface 10 fails.
# Display static routes on Switch A.
<SwitchA> display ip routing-table protocol static
Summary count : 1
Static Routing table status : <Active>
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
120.1.1.0/24 Static 65 0 10.1.1.100 Vlan11
Static Routing table status : <Inactive>
Summary count : 0
The output shows that Switch A communicates with Switch B through VLAN-interface 11.
BFD for static routes configuration example (indirect next hop)
Network requirements
Figure 4 shows the network topology as follows:
· Switch A has a route to interface Loopback 1 (2.2.2.9/32) on Switch B, with the output interface VLAN-interface 10.
· Switch B has a route to interface Loopback 1 (1.1.1.9/32) on Switch A, with the output interface VLAN-interface 12.
· Switch D has a route to 1.1.1.9/32, with the output interface VLAN-interface 10, and a route to 2.2.2.9/32, with the output interface VLAN-interface 12.
Configure the following:
· Configure a static route to subnet 120.1.1.0/24 on Switch A.
· Configure a static route to subnet 121.1.1.0/24 on Switch B.
· Enable BFD for both routes.
· Configure a static route to subnet 120.1.1.0/24 and a static route to subnet 121.1.1.0/24 on both Switch C and Switch D.
When the link between Switch A and Switch B through Switch D fails, BFD can detect the failure immediately. Switch A then communicates with Switch B through Switch C.
Table 2 Interface and IP address assignment
|
Device |
Interface |
IP address |
|
Switch A |
VLAN-interface 10 |
12.1.1.1/24 |
|
Switch A |
VLAN-interface 11 |
10.1.1.102/24 |
|
Switch A |
Loopback 1 |
1.1.1.9/32 |
|
Switch B |
VLAN-interface 12 |
11.1.1.1/24 |
|
Switch B |
VLAN-interface 13 |
13.1.1.1/24 |
|
Switch B |
Loopback 1 |
2.2.2.9/32 |
|
Switch C |
VLAN-interface 11 |
10.1.1.100/24 |
|
Switch C |
VLAN-interface 13 |
13.1.1.2/24 |
|
Switch D |
VLAN-interface 10 |
12.1.1.2/24 |
|
Switch D |
VLAN-interface 12 |
11.1.1.2/24 |
Configuration procedure
1. Configure IP addresses for interfaces. (Details not shown.)
2. Configure static routes and BFD:
# Configure static routes on Switch A and enable BFD control packet mode for the static route that traverses Switch D.
<SwitchA> system-view
[SwitchA] bfd multi-hop min-transmit-interval 500
[SwitchA] bfd multi-hop min-receive-interval 500
[SwitchA] bfd multi-hop detect-multiplier 9
[SwitchA] ip route-static 120.1.1.0 24 2.2.2.9 bfd control-packet bfd-source 1.1.1.9
[SwitchA] ip route-static 120.1.1.0 24 vlan-interface 11 10.1.1.100 preference 65
[SwitchA] quit
# Configure static routes on Switch B and enable BFD control packet mode for the static route that traverses Switch D.
<SwitchB> system-view
[SwitchB] bfd multi-hop min-transmit-interval 500
[SwitchB] bfd multi-hop min-receive-interval 500
[SwitchB] bfd multi-hop detect-multiplier 9
[SwitchB] ip route-static 121.1.1.0 24 1.1.1.9 bfd control-packet bfd-source 2.2.2.9
[SwitchB] ip route-static 121.1.1.0 24 vlan-interface 13 13.1.1.2 preference 65
[SwitchB] quit
# Configure static routes on Switch C.
<SwitchC> system-view
[SwitchC] ip route-static 120.1.1.0 24 13.1.1.1
[SwitchC] ip route-static 121.1.1.0 24 10.1.1.102
# Configure static routes on Switch D.
<SwitchD> system-view
[SwitchD] ip route-static 120.1.1.0 24 11.1.1.1
[SwitchD] ip route-static 121.1.1.0 24 12.1.1.1
Verifying the configuration
# Display BFD sessions on Switch A.
<SwitchA> display bfd session
Total Session Num: 1 Up Session Num: 1 Init Mode: Active
IPv4 session working in control packet mode:
LD/RD SourceAddr DestAddr State Holdtime Interface
4/7 1.1.1.9 2.2.2.9 Up 2000ms N/A
The output shows that the BFD session has been created.
# Display the static routes on Switch A.
<SwitchA> display ip routing-table protocol static
Summary count : 1
Static Routing table status : <Active>
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
120.1.1.0/24 Static 60 0 12.1.1.2 Vlan10
Static Routing table status : <Inactive>
Summary count : 0
The output shows that Switch A communicates with Switch B through VLAN-interface 10. Then the link over VLAN-interface 10 fails.
# Display static routes on Switch A.
<SwitchA> display ip routing-table protocol static
Summary count : 1
Static Routing table status : <Active>
Summary count : 1
Destination/Mask Proto Pre Cost NextHop Interface
120.1.1.0/24 Static 65 0 10.1.1.100 Vlan11
Static Routing table status : <Inactive>
Summary count : 0
The output shows that Switch A communicates with Switch B through VLAN-interface 11.
Static route FRR configuration example
Network requirements
As shown in Figure 5, configure static routes on Switch A, Switch B, and Switch C, and configure static route FRR. When Link A becomes unidirectional, traffic can be switched to Link B immediately.
Table 3 Interface and IP address assignment
|
Device |
Interface |
IP address |
|
Switch A |
VLAN-interface 100 |
12.12.12.1/24 |
|
Switch A |
VLAN-interface 200 |
13.13.13.1/24 |
|
Switch A |
Loopback 0 |
1.1.1.1/32 |
|
Switch B |
VLAN-interface 101 |
24.24.24.4/24 |
|
Switch B |
VLAN-interface 200 |
13.13.13.2/24 |
|
Switch B |
Loopback 0 |
4.4.4.4/32 |
|
Switch C |
VLAN-interface 100 |
12.12.12.2/24 |
|
Switch C |
VLAN-interface 101 |
24.24.24.2/24 |
Configuration procedure
1. Configure IP addresses for interfaces. (Details not shown.)
2. Configure static route FRR on link A by using one of the following methods:
¡ (Method 1.) Specify a backup next hop for static route FRR:
# Configure a static route on Switch A, and specify VLAN-interface 100 as the backup output interface and 12.12.12.2 as the backup next hop.
<SwitchA> system-view
[SwitchA] ip route-static 4.4.4.4 32 vlan-interface 200 13.13.13.2 backup-interface vlan-interface 100 backup-nexthop 12.12.12.2
# Configure a static route on Switch B, and specify VLAN-interface 101 as the backup output interface and 24.24.24.2 as the backup next hop.
<SwitchB> system-view
[SwitchB] ip route-static 1.1.1.1 32 vlan-interface 200 13.13.13.1 backup-interface vlan-interface 101 backup-nexthop 24.24.24.2
¡ (Method 2.) Configure static route FRR to automatically select a backup next hop:
# Configure static routes on Switch A, and enable static route FRR.
<SwitchA> system-view
[SwitchA] ip route-static 4.4.4.4 32 vlan-interface 200 13.13.13.2
[SwitchA] ip route-static 4.4.4.4 32 vlan-interface 100 12.12.12.2 preference 70
[SwitchA] ip route-static fast-reroute auto
# Configure static routes on Switch B, and enable static route FRR.
<SwitchB> system-view
[SwitchB] ip route-static 1.1.1.1 32 vlan-interface 200 13.13.13.1
[SwitchB] ip route-static 1.1.1.1 32 vlan-interface 101 24.24.24.2 preference 70
[SwitchB] ip route-static fast-reroute auto
3. Configure static routes on Switch C.
<SwitchC> system-view
[SwitchC] ip route-static 4.4.4.4 32 vlan-interface 101 24.24.24.4
[SwitchC] ip route-static 1.1.1.1 32 vlan-interface 100 12.12.12.1
Verifying the configuration
# Display route 4.4.4.4/32 on Switch A to view the backup next hop information.
[SwitchA] display ip routing-table 4.4.4.4 verbose
Summary count : 1
Destination: 4.4.4.4/32
Protocol: Static
Process ID: 0
SubProtID: 0x0 Age: 04h20m37s
Cost: 0 Preference: 60
IpPre: N/A QosLocalID: N/A
Tag: 0 State: Active Adv
OrigTblID: 0x0 OrigVrf: default-vrf
TableID: 0x2 OrigAs: 0
NibID: 0x26000002 LastAs: 0
AttrID: 0xffffffff Neighbor: 0.0.0.0
Flags: 0x1008c OrigNextHop: 13.13.13.2
Label: NULL RealNextHop: 13.13.13.2
BkLabel: NULL BkNextHop: 12.12.12.2
SRLabel: NULL BkSRLabel: NULL
SIDIndex: NULL InLabel: NULL
Tunnel ID: Invalid Interface: Vlan-interface200
BkTunnel ID: Invalid BkInterface: Vlan-interface100
FtnIndex: 0x0 TrafficIndex: N/A
Connector: N/A PathID: 0x0
LinkCost: 0 MicroSegID: 0
RealFIRType: Normal RealThres: 0
# Display route 1.1.1.1/32 on Switch B to view the backup next hop information.
[SwitchB] display ip routing-table 1.1.1.1 verbose
Summary count : 1
Destination: 1.1.1.1/32
Protocol: Static
Process ID: 0
SubProtID: 0x0 Age: 04h20m37s
Cost: 0 Preference: 60
IpPre: N/A QosLocalID: N/A
Tag: 0 State: Active Adv
OrigTblID: 0x0 OrigVrf: default-vrf
TableID: 0x2 OrigAs: 0
NibID: 0x26000002 LastAs: 0
AttrID: 0xffffffff Neighbor: 0.0.0.0
Flags: 0x1008c OrigNextHop: 13.13.13.1
Label: NULL RealNextHop: 13.13.13.1
BkLabel: NULL BkNextHop: 24.24.24.2
SRLabel: NULL BkSRLabel: NULL
SIDIndex: NULL InLabel: NULL
Tunnel ID: Invalid Interface: Vlan-interface200
BkTunnel ID: Invalid BkInterface: Vlan-interface101
FtnIndex: 0x0 TrafficIndex: N/A
Connector: N/A PathID: 0x0
LinkCost: 0 MicroSegID: 0
RealFIRType: Normal RealThres: 0
Configuring a default route
A default route is used to forward packets that do not match any specific routing entry in the routing table. Without a default route, packets that do not match any routing entries are discarded and an ICMP destination-unreachable packet is sent to the source.
A default route can be configured in either of the following ways:
· The network administrator can configure a default route with both destination and mask being 0.0.0.0. For more information, see "Configuring static routing."
· Some dynamic routing protocols, such as OSPF, RIP, and IS-IS, can generate a default route. For example, an upstream router running OSPF can generate a default route and advertise it to other routers. These routers install the default route with the next hop being the upstream router. For more information, see the respective chapters on these routing protocols in this configuration guide.
As shown in Figure 6, Device B is the next hop for packets from Device A to Device C, Device D, and Device E. You can configure a default route on Device A to replace the three static routes from Device A to Device C, Device D, and Device E, respectively. Then, packets that do not match any other routes will be forwarded based on the default route.
The next hop address, destination address, and subnet mask of the default route configured on Device A are 1.1.1.2, 0.0.0.0, and 0.0.0.0, respectively.
Figure 6 Configuring a default route
