Out of Resource Handling of FIB Resources
The main function of the FIB within routers/line-cards is to map destination IP prefixes/labels to potential egress interfaces. In order to achieve this, the FIB maintains multiple databases or hardware tables, such as:
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Forward Equivalence Class (FEC) and the Equal Cost Multi-Path Forward Equivalence Class (ECMP FEC): This database mainly stores information related to the IPv4 and IPv6 prefixes that the router has learnt. When a traffic packet reaches the router, it performs a FIB lookup on the destination prefix of the incoming packet. This lookup results in the FEC or ECMP FEC object for that particular prefix and it provides information about the egress interface on the router through which the packet can reach its destination.
OOR Protection Mode
When the FIB resource usage exceeds the red threshold, the system enters OOR protection mode.
In FEC OOR protection mode, the router doesn’t allocate any FEC objects when it learns a new prefix, but assigns a pre-created drop FEC instead. The router drops incoming packets with destination IP addresses that were assigned the drop FEC.
In ECMP FEC OOR protection mode, the router chooses only the first path among multiple paths to forward traffic. When FEC or ECMP FEC usage drops below yellow threshold, the router reprograms the affected prefixes to normal FEC or ECMP FEC. Thereafter, the router resumes traffic flow.
Configuration Steps to Change OOR Threshold Levels
The following section shows how to change the default threshold levels for OOR handling.
Router# conf t
Router(config)# oor hw threshold red 90
Router(config)# oor hw threshold yellow 75
Router(config)# commitRelease Stale FEC Resources
To release the stale FEC resources, execute the following command:
Router# clear cefVerification of FEC Resources
Use the show controllers npu resources command to verify FIB resources.
The OOR State in the output of the show controllers npu resources command changes when the router reaches an OOR situation. The OOR State changes from Green to Yellow, and finally to Red depending on the utilization of FEC or ECMP FEC resources.
Router# show controllers npu resources fec location 0/0/CPU0
HW Resource Information
Name : fec
Asic Type : Qumran
NPU-0
OOR Summary
Estimated Max Entries : 126976
Red Threshold : 95 %
Yellow Threshold : 80 %
OOR State : Green
Bank Info : FEC
OFA Table Information
(May not match HW usage)
ipnhgroup : 43058
ip6nhgroup : 2
edpl : 0
limd : 0
punt : 19
iptunneldecap : 0
ipmcroute : 1
ip6mcroute : 0
ipnh : 0
ip6nh : 0
mplsmdtbud : 0
ipvrf : 2
ippbr : 0
redirectvrf : 0
l2protect : 0
l2bridgeport : 0
Current Hardware Usage
Name: fec
Estimated Max Entries : 126976
Total In-Use : 43082 (33 %)
OOR State : Green
Bank Info : FEC
Name: hier_0
Estimated Max Entries : 126976
Total In-Use : 43082 (33 %)
OOR State : Green
Bank Info : FECVerification of EEDB Resources
The router processes several entries and often stores these entries in the form of tables. These tables are further divided into smaller tables. These smaller tables are called as banks. The banks are often named as bank_0, bank_1, bank_2, and so on. Router segregates the entries through these banks.
 Note |
bank_0 will always be indicated as completely utilized and in Red OOR state on the following routers and line cards:
This complete utilization of bank_0 must be ignored since it is reserved for internal usage regardless of the router configuration. |
Use show controllers npu resources encap command to verify the usage of EEDB resources.
The OOR State in the output of the show controllers npu resources encap command changes when the router reaches an OOR situation. The OOR State changes from Green to Yellow, and finally to Red depending on the utilization of the EEDB resources.
Router# show controllers npu resources encap location 1/0/CPU0
HW Resource Information
Name : encap
Asic Type : Jericho
NPU-0
OOR Summary
Red Threshold : 95 %
Yellow Threshold : 80 %
OFA Table Information
(May not match HW usage)
ipnh : 13
ip6nh : 0
mplsnh : 0
llnh : 0
srv6nh : 0
ipvrf : 0
mplsmdtbud : 0
iptunnelencap : 0
tep : 0
Current Hardware Usage
Name: encap
Name: bank_0
Estimated Max Entries : 4096
Total In-Use : 4096 (100 %)
OOR State : Red
OOR State Change Time : 2022.Mar.15 05:33:14 UTC
Bank Info : phase=2 extended=no
Name: bank_1
Estimated Max Entries : 4096
Total In-Use : 4 (0 %)
OOR State : Green
Bank Info : phase=8 extended=no
Name: bank_2
Estimated Max Entries : 4096
Total In-Use : 0 (0 %)
OOR State : Green
Bank Info : phase=0 extended=no
Name: bank_3
Estimated Max Entries : 4096
Total In-Use : 0 (0 %)
OOR State : Green
Bank Info : phase=0 extended=no
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