Contents

Basic IP forwarding commands· 1

display fib· 1

forwarding arp-packet destination· 3

forwarding nd-packet destination· 4

forwarding hop-limit-exceeded destination· 4

forwarding hop-limit-unvaried destination· 5

forwarding split-horizon· 6

forwarding ttl-exceeded-packet destination· 7

forwarding ttl-unvaried destination· 7

ip forwarding· 8

ip forwarding ttl-unvaried· 9

 

Basic IP forwarding commands

display fib

Use display fib to display FIB entries.

Syntax

display fib [ vpn-instance vpn-instance-name ] [ ip-address [ mask | mask-length ] ]

Views

Any view

Predefined user roles

network-admin

network-operator

Parameters

vpn-instance vpn-instance-name: Specifies an MPLS L3VPN instance by its name, a case-sensitive string of 1 to 31 characters. To display the FIB entries for the public network, do not specify any VPN instance.

ip-address: Displays the FIB entry that matches the specified destination IP address.

mask: Specifies the mask for the IP address.

mask-length: Specifies the mask length for the IP address. The value range is 0 to 32.

Usage guidelines

If you specify an IP address without a mask or mask length, this command displays the longest matching FIB entry.

If you specify an IP address and a mask or mask length, this command displays the exactly matching FIB entry.

Examples

# Display all FIB entries of the public network.

<Sysname> display fib

Route destination count: 5

Directly-connected host count: 0

 

Flag:

  U:Usable    G:Gateway   H:Host   B:Blackhole   D:Dynamic   S:Static

  R:Relay     F:FRR

 

Destination/Mask   Nexthop         Flag     OutInterface/Token       Label

0.0.0.0/32         127.0.0.1       UH       InLoop0                  Null

1.1.1.0/24         192.168.126.1   USGF     M-GE0/0/0                Null

127.0.0.0/8        127.0.0.1       U        InLoop0                  Null

127.0.0.0/32       127.0.0.1       UH       InLoop0                  Null

127.0.0.1/32       127.0.0.1       UH       InLoop0                  Null

# Display the FIB entries for VPN vpn1.

<Sysname> display fib vpn-instance vpn1

Route destination count: 8

Directly-connected host count: 0

 

Flag:

  U:Usable   G:Gateway   H:Host   B:Blackhole   D:Dynamic   S:Static

  R:Relay     F:FRR

 

Destination/Mask   Nexthop         Flag     OutInterface/Token      Label

0.0.0.0/32         127.0.0.1       UH       InLoop0                  Null

20.20.20.0/24      20.20.20.25     U        M-GE0/0/0                Null

20.20.20.0/32      20.20.20.25     UBH      M-GE0/0/0                Null

20.20.20.25/32     127.0.0.1       UH       InLoop0                  Null

20.20.20.25/32     20.20.20.25     H        M-GE0/0/0                Null

20.20.20.255/32    20.20.20.25     UBH      M-GE0/0/0                Null

20.20.20.255/32    1000:2000:3000:4000:5000:6000:7000:8000 UBH      MGE0

/0/0                Null

# Display the FIB entries matching the destination IP address 10.2.1.1.

<Sysname> display fib 10.2.1.1

FIB entry count: 1

 

Flag:

  U:Usable   G:Gateway   H:Host   B:Blackhole   D:Dynamic   S:Static

  R:Relay     F:FRR

 

Destination/Mask   Nexthop         Flag     OutInterface/Token       Label

10.2.1.1/32        127.0.0.1       UH       InLoop0                  Null

Table 1 Command output

Field	Description
Route destination count	Number of route destination addresses.
Directly-connected host count	Number of directly connected hosts learned by features such as ARP.
FIB entry count	Total number of FIB entries.
Destination/Mask	Destination address and the mask length.
Nexthop	Next hop address.
Flag	Flags of routes: ·     U—Usable route. ·     G—Gateway route. ·     H—Host route. ·     B—Blackhole route. ·     D—Dynamic route. ·     S—Static route. ·     R—Relay route. ·     F—Fast reroute.
OutInterface/Token	Output interface/LSP index number.
Label	Inner label.

 

forwarding arp-packet destination

Use forwarding arp-packet destination to enable forwarding ARP packets with a specific destination address to a specific VXLAN tunnel.

Use undo forwarding arp-packet destination to restore the default.

Syntax

forwarding arp-packet destination [ vpn-instance vpn-instance-name ] ip-address interface tunnel number

undo forwarding arp-packet destination [ vpn-instance vpn-instance-name ] ip-address

Default

The device delivers ARP packets to CPU.

Views

System view

Predefined user roles

network-admin

Parameters

vpn-instance vpn-instance-name: Specifies the MPLS L3VPN instance to which the specified destination IP address belongs. The vpn-instance-name argument is a case-sensitive string of 1 to 31 characters. If the specified destination IPv6 address belongs to the public network and all VPN instances, do not specify this option.

ip-address: Specifies a destination IP address.

interface tunnel number: Specifies a tunnel interface by its number. The value range for the number argument is 1 to 13. The actual number of tunnel interfaces that can be created depend on memory usage and the total number of interfaces.

Usage guidelines

In a scenario where ARP flooding suppression is enabled, a device discards an ARP packet if the following conditions exist:

·     The ARP packet uses the device's MAC address as the destination MAC address.

·     The ARP packet uses another device's IPv4 address as the destination IPv4 address.

When the device is supposed to such packets to a specific VXLAN tunnel, perform this task for that device.

Make sure the specified tunnel interface is a manual created VXLAN over IPv4 tunnel.

Examples

# Forward ARP packets destined for 192.168.1.2 in VPN instance vpn1 to tunnel interface 1.

<Sysname> system-view

[Sysname] forwarding arp-packet destination vpn-instance vpn1 192.168.1.2 interface tunnel 1

forwarding nd-packet destination

Use forwarding nd-packet destination to enable forwarding ND packets with a specific destination address to a specific VXLAN tunnel.

Use undo forwarding nd-packet destination to restore the default.

Syntax

forwarding nd-packet destination [ vpn-instance vpn-instance-name ] ipv6-address interface tunnel number

undo forwarding nd-packet destination [ vpn-instance vpn-instance-name ] ipv6-address

Default

The device delivers ND packets to CPU.

Views

System view

Predefined user roles

network-admin

Parameters

vpn-instance vpn-instance-name: Specifies the MPLS L3VPN instance to which the specified destination IPv6 address belongs. The vpn-instance-name argument is a case-sensitive string of 1 to 31 characters. If the specified destination IPv6 address belongs to the public network and all VPN instances, do not specify this option.

ip-address: Specifies a destination IPv6 address.

interface tunnel number: Specifies a tunnel interface by its number. The value range for the number argument is 1 to 13. The actual number of tunnel interfaces that can be created depend on memory usage and the total number of interfaces.

Usage guidelines

In a scenario where ND flooding suppression is enabled, a device discards an ND packet if the following conditions exist:

·     The ND packet uses the device's MAC address as the destination MAC address.

·     The ND packet uses another device's IPv6 address as the destination IPv6 address.

When the device is supposed to such packets to a specific VXLAN tunnel, perform this task for that device.

Make sure the specified tunnel interface is a manual created VXLAN over IPv4 tunnel.

Examples

# Forward ND packets destined for 4001::1 in VPN instance vpn1 to tunnel interface 1.

<Sysname> system-view

[Sysname] forwarding nd-packet destination vpn-instance vpn1 4001::1 interface tunnel 1

forwarding hop-limit-exceeded destination

Use forwarding hop-limit-exceeded destination to enable the device to forward IPv6 packets with hop limit 1 if the packets are destined for a specific IPv6 address. These IPv6 packets are not processed by CPU.

Use undo forwarding hop-limit-exceeded destination to restore the default.

Syntax

forwarding hop-limit-exceeded destination [ vpn-instance vpn-instance-name ] ipv6-address

undo forwarding hop-limit-exceeded destination [ vpn-instance vpn-instance-name ] ipv6-address

Default

The device delivers IPv6 packets with hop limit 1 to CPU.

Views

System view

Predefined user roles

network-admin

Parameters

vpn-instance vpn-instance-name: Specifies the MPLS L3VPN instance to which the specified destination IPv6 address belongs. The vpn-instance-name argument is a case-sensitive string of 1 to 31 characters. If the specified destination IPv6 address belongs to the public network and all VPN instances, do not specify this option.

ipv6-address: Specifies a destination IPv6 address.

Usage guidelines

This feature is typically configured on a device that acts as the gateway in the following scenario:

·     The device directly connects to an internal device.

·     The internal device wishes to receive IPv6 packets destined for a specific IPv6 address, but it do not care about the HopLimit value in the packets.

Upon receiving an IPv6 packet with hop limit 1, the device forwards the packet directly if the packet is destined for the specified destination IPv6 address.

Examples

# Directly forward IPv6 packets with hop limit 1 if the packets are destined for IPv6 address 1::1.

<Sysname> system-view

[Sysname] forwarding hop-limit-exceeded destination 1::1

forwarding hop-limit-unvaried destination

Use forwarding hop-limit-unvaried destination to keep the value unchanged in the Hop Limit field of a received packet if the packet is destined for a specific IPv6 address.

Use undo forwarding hop-limit-unvaried destination to restore the default.

Syntax

forwarding hop-limit-unvaried destination [ vpn-instance vpn-instance-name ] ipv6-address

undo forwarding hop-limit-unvaried [ vpn-instance vpn-instance-name ] ipv6-address

Default

The device decrements the value in the Hop Limit field of a received packet by one.

Views

System view

Predefined user roles

network-admin

Parameters

vpn-instance vpn-instance-name: Specifies the MPLS L3VPN instance to which the specified destination IPv6 address belongs. The vpn-instance-name argument is a case-sensitive string of 1 to 31 characters. If the specified destination IPv6 address belongs to the public network and all VPN instances, do not specify this option.

ipv6-address: Specifies a destination IPv6 address.

Examples

# Enable the device to keep the value unchanged in the Hop Limit field of a received packet if the packet is destined for 1::1.

<Sysname> system-view

[Sysname] forwarding hop-limit-unvaried destination 1::1

[Sysname] forwarding hop-limit-unvaried destination vpn-instance vpn1 1::2

forwarding split-horizon

Use forwarding split-horizon to enable split horizon forwarding.

Use undo forwarding split-horizon to disable split horizon forwarding.

 

NOTE: Only the R5212 and later versions support this feature.

 

Syntax

forwarding split-horizon

undo forwarding split-horizon

Default

Split horizon forwarding is disabled.

Views

System view

Layer 2 interface view

Layer 3 interface view

Predefined user roles

network-admin

Usage guidelines

This feature prevents IPv4, IPv6, and MPLS packets from being forwarded out of the physical interface on which they were received, avoiding network loops.

You can enable this feature globally in system view or enable this feature for a specific interface in interface view. This feature takes effect on an interface if it is enabled for the interface or enabled globally.

To disable this feature, you must disable it in both system view and interface view.

Examples

# Enable split horizon forwarding globally.

<Sysname> system-view

[Sysname] forwarding split-horizon

forwarding ttl-exceeded-packet destination

Use forwarding ttl-exceeded-packet destination to enable the device to forward IPv4 packets with TTL 1 if the packets are destined for a specific IPv4 address. These IPv4 packets are not processed by CPU.

Use undo forwarding ttl-exceeded-packet destination to restore the default.

Syntax

forwarding ttl-exceeded-packet destination [ vpn-instance vpn-instance-name ] ip-address

undo forwarding ttl-exceeded-packet destination [ vpn-instance vpn-instance-name ] ip-address

Default

The device delivers IPv4 packets with TTL 1 to CPU.

Views

System view

Predefined user roles

network-admin

Parameters

vpn-instance vpn-instance-name: Specifies the MPLS L3VPN instance to which the destination IPv4 address belongs. The vpn-instance-name argument is a case-sensitive string of 1 to 31 characters. If the destination IPv4 address belongs to the public network and all VPN instances, do not specify this option.

ip-address: Specifies a destination IPv4 address.

Usage guidelines

This feature is typically configured on a device that acts as the gateway in the following scenario:

·     The device directly connects to an internal server.

·     The internal server wishes to receive IPv4 packets destined for a specific IPv4 address, but it does not care about the TTL value in the packets.

Upon receiving an IPv4 packet with TTL 1, the device forwards the packet directly if the packet is destined for the specified destination IPv4 address.

Examples

# Directly forward IPv4 packets with TTL 1 if the packets are destined for 10.1.1.2.

<Sysname> system-view

[Sysname] forwarding ttl-exceeded-packet destination 10.1.1.2

forwarding ttl-unvaried destination

Use forwarding ttl-unvaried destination to keep the value unchanged in the TTL field of a received packet if the packet is destined for a specific IPv4 address.

Use undo forwarding ttl-unvaried destination to restore the default.

Syntax

forwarding ttl-unvaried destination [ vpn-instance vpn-instance-name ] ip-address

undo forwarding ttl-unvaried destination [ vpn-instance vpn-instance-name ] ip-address

Default

The device decrements the value in the TTL field of a received packet by one.

Views

System view

Predefined user roles

network-admin

Parameters

vpn-instance vpn-instance-name: Specifies the MPLS L3VPN instance to which the specified destination IPv4 address belongs. The vpn-instance-name argument is a case-sensitive string of 1 to 31 characters. If the specified destination IPv4 address belongs to the public network and all VPN instances, do not specify this option.

ip-address: Specifies a destination IPv4 address.

Examples

# Enable the device to keep the value unchanged in the TTL field of a received packet if the packet is destined for 192.168.20.195.

<Sysname> system-view

[Sysname] forwarding ttl-unvaried destination 192.168.20.195

[Sysname] forwarding ttl-unvaried destination vpn-instance vpn1 192.168.20.195

ip forwarding

Use ip forwarding to enable IPv4 packet forwarding on an interface that has no IPv4 address configured.

Use undo ip forwarding to disable IPv4 packet forwarding on an interface that has no IPv4 address configured.

Syntax

ip forwarding

undo ip forwarding

Default

If an interface has no IPv4 address configured, it cannot forward IPv4 packets.

Views

Interface view

Predefined user roles

network-admin

Usage guidelines

On a device that supports both IPv4 and IPv6, the next hop of an IPv4 packet might be an IPv4 address or an IPv6 address. If the output interface has no IPv4 address configured, the interface cannot forward the IPv4 packet. To resolve this issue, execute this command on the interface. This feature allows the interface to forward IPv4 packets even though the interface has no IPv4 address configured.

Examples

# Enable IPv4 packet forwarding on HundredGigE 1/0/1 that has no IPv4 address configured.

<Sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] ip forwarding

ip forwarding ttl-unvaried

Use ip forwarding ttl-unvaried to keep the value unchanged in the TTL or Hop Limit field of packets passing through a Layer 3 forwarding device.

Use undo ip forwarding ttl-unvaried to restore the default.

Syntax

ip forwarding ttl-unvaried

undo ip forwarding ttl-unvaried

Default

The value in the TTL or Hop Limit field of a packet is decremented by one when the packet passes through a Layer 3 forwarding device.

Views

System view

Predefined user roles

network-admin

Usage guidelines

By default, upon receiving a packet, the forward device decrements the TTL or hop limit in the packet by one to avoid endless packet forwardings on the network. However, to ensure correct flow analysis for traffic division, the fields of a packet are supposed to be unchanged as many as possible before the packet reaches the data analyzer. To meet this requirement, use this command.

This feature does not take effect on Layer 3 packets in an Overlay network.

Examples

# Keep the value unchanged in the TTL or Hop Limit field of packets passing through a Layer 3 forwarding device.

<Sysname> system-view

[Sysname] ip forwarding ttl-unvaried