Displaying and Maintaining FIB Tables

Context

Unless otherwise stated, FIB tables in this document refer to unicast FIB tables.

A device selects routes according to its IP routing table and forwards packets according to FIB tables. If the number of entries in a FIB table reaches or exceeds the limit, that is, the FIB table is overloaded, new active routes cannot be delivered to the FIB table, affecting packet forwarding.

Procedure

Check FIB entries.
- Run the display fib [ slot-id ] [ vpn-instance vpn-instance-name ] [ verbose ] command to check IPv4 FIB entries.
- Run the display fib [ vpn-instance vpn-instance-name ] acl acl-number [ verbose ] command to check IPv4 FIB entries that match a specified ACL.
- Run the display fib [ vpn-instance vpn-instance-name ] ip-prefix prefix-name [ verbose ] command to check IPv4 FIB entries that match a specified IP prefix list.
- Run the display fib [ slot-id ] [ vpn-instance vpn-instance-name ] destination-address1 [ verbose ] command to check IPv4 FIB entries that match a specified destination IP address.
- Run the display fib [ slot-id ] [ vpn-instance vpn-instance-name ] destination-address1 destination-mask1 [ verbose ] command to check IPv4 FIB entries that exactly match a specified destination IP address and mask.
- Run the display fib [ slot-id ] [ vpn-instance vpn-instance-name ] destination-address1 longer [ verbose ] command to check all IPv4 FIB entries that match destination IP addresses in the natural mask range.
- Run the display fib [ slot-id ] [ vpn-instance vpn-instance-name ] destination-address1 destination-mask1 longer [ verbose ] command to check all IPv4 FIB entries that match destination IP addresses in a specified mask range.
- Run the display fib [ slot-id ] [ vpn-instance vpn-instance-name ] destination-address1 destination-mask1 destination-address2 destination-mask2 [ verbose ] command to check IPv4 FIB entries that match destination IP addresses in the range of destination-address1 destination-mask1 and destination-address2 destination-mask2.
- Run the display fib [ vpn-instance vpn-instance-name ] next-hop ip-address command to check IPv4 FIB entries that match a specified next-hop IP address.
- Run the display fib [ slot-id ] [ vpn-instance vpn-instance-name ] statistics command to check the total number of IPv4 FIB entries.
- Run the display fib [ slot-id ] statistics all command to check IPv4 FIB entry statistics.
- Run the display ipv6 fib [ slot-id ] [ vpn-instance vpn-instance-name ] [ verbose ] command to check IPv6 FIB entries.
- Run the display ipv6 fib [ slot-id ] [ vpn-instance vpn-instance-name ] ipv6-address [ verbose ] command to check IPv6 FIB entries that match a specified destination IPv6 address.
- Run the display ipv6 fib [ slot-id ] [ vpn-instance vpn-instance-name ] ipv6-address prefix-length [ verbose ] command to check IPv6 FIB entries that exactly match a specified destination IPv6 address and mask.
- Run the display ipv6 fib [ slot-id ] [ vpn-instance vpn-instance-name ] statistics command to check the total number of IPv6 FIB entries.
- Run the display ipv6 fib [ slot-id ] statistics all command to check IPv6 FIB entry statistics.
Maintain FIB tables.
- Enable the alarm function for the IPv4 route prefix usage and set the alarm threshold.
  1. Run system-view
    
    The system view is displayed.
  2. Run fib threshold-alarm upper-limit upper-limit-value lower-limit lower-limit-value
    
    The alarm function for the IPv4 route prefix usage is enabled and the alarm threshold is set.
    
    By default, the alarm function for IPv4 route prefix usage is enabled. The upper alarm threshold is 85% and the lower alarm threshold is 75%.
- Configure the resource mode of the extended entry space register to adjust the IPv4 and IPv6 FIB table sizes.
  1. (Optional) Run the display resource-mode configuration command to check the resource mode configuration of the extended entry space.
  2. Run the system-view command to enter the system view.
  3. Configure the resource allocation mode of the extended entry space.
    - On the S5720-EI, run the assign resource-mode { enhanced-mac | enhanced-ipv4 | enhanced-ipv6 } [ slot slot-id | all ] command to configure the resource mode.
    - On the S6720-EI and S6720S-EI, run the assign resource-mode { enhanced-mac | enhanced-arp | enhanced-ipv4 | ipv4-ipv6 6:1 | super-arp } [ slot slot-id | all ] command to configure the resource mode.
    By default, the resource allocation mode of the S5720-EI is enhanced-mac and that of the S5720-HI, S5730-HI, S5731-H, S5731S-H, S5732-H, S5731-S, S5731S-S, S6730-S, S6730S-S, S6730-H, S6730S-H, S6720-HI, S6720-EI, and S6720S-EI is enhanced-arp.
- Configure periodic refresh of FIB entries.
  1. Run system-view
    
    The system view is displayed.
  2. Run undo fib regularly-refresh disable
    
    Periodic refresh of FIB entries is enabled.
    
    By default, periodic refresh of FIB entries is enabled.
  3. Run fib regularly-refresh { interval interval [ entry-number entry-number ] | entry-number entry-number | cycle-interval cycle-interval }
    
    The entire FIB entry update interval, FIB entry update interval per cycle, and the number of FIB entries updated per cycle are configured.
    
    By default, the entire FIB entry update interval is 1 minute, the FIB entry update interval per cycle is 1 second, and the number of FIB entries updated per cycle is 50.
- Configure periodic refresh of IPv6 FIB entries.
  1. Run system-view
    
    The system view is displayed.
  2. Run undo ipv6 fib regularly-refresh disable
    
    Periodic refresh of IPv6 FIB entries is enabled.
  3. Run ipv6 fib regularly-refresh { interval interval | entry-number entry-number | cycle-interval cycle-interval }
    
    The entire IPv6 FIB entry update interval, IPv6 FIB entry update interval per cycle, and the number of IPv6 FIB entries updated per cycle are configured.
    
    By default, the entire IPv6 FIB entry update interval is 1 minute, the IPv6 FIB entry update interval per cycle is 1 second, and the number of IPv6 FIB entries updated per cycle is 50.