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When S9306 Switches Are Deployed on a Ring Network, Exceed the Hardware Specifications

Publication Date:  2013-12-31 Views:  448 Downloads:  0
Issue Description
S9306 switches are deployed on a ring network and enabled with OSPF. Load balancing of OSPF equal-cost routes triggers established of two MPLS LSPs. As a result, the number of LSPs exceeds the hardware specification on LSPs, and an insufficient resource alarm is displayed.
Alarm Information
NA_SR_MAD_TOR01%%01LSPM/4/REACHLICENCELIMIT(l)[53]:LSRType=Ingress and LSPType=LSPM LSP reached the upper limit of the license.
Handling Process
1. Query logs. The following log is found:
LSPM/4/REACHLICENCELIMIT:LSRType=[LSRType1] and LSPType=[LSRType2] reached the upper limit of the license.

The upper limit of the license was reached.
A card on the S9300 supports a maximum of 8K MPLS LSPs. However, the number of LSPs established on TOR01 is much greater than 8K, most of which are transmit LSPs. The number of transmit LSPs is almost a double of that on switches on the ring network. Double transmit LSPs may have been established.

2. Check the MPLS label entries and routing entries on TOR01.
On the live network, LDP is used to distribute MPLS labels and establish LSPs to forward packets. Label distribution is triggered by an Interior Gateway Protocol (IGP). In this case, OSPF (an IGP) together with LDP triggers label distribution. Check the OSPF routing table on TOR01. A large number of OSPF equal-cost routes exist on TOR01. This triggers LDP label distribution, and LSPs are established for load balancing. The number of LSPs is doubled. However, MAT01, PRO01, and other devices do not have OSPF equal-cost routes.

3. Change the cost value on an interface enabled with OSPF. In this way, OSPF equal-cost routes in load balancing mode are changed to active and standby routes. The number of new transmit LSPs decreases a lot, and the alarm is cleared.
Root Cause
A large number of equal-cost routes exist in the OSPF routing table on TOR01. This triggers Label Distribution Protocol (LDP) label distribution, and LSPs are established for load balancing. The number of LSPs is doubled.
During network planning, pay attention to device performance indicators and specification limits, and focus on load balancing of routing protocols and potential impact on device performance.