Symptom
Dropping of ISIS packet type LSP of exactly size 270 bytes on ingress.
Missing ISIS prefixes in the routing table on a router.
Constant retransmitting of ISIS LSPs between routers.
Conditions
NCS platform family, linecard with Jericho 2 asics.These are linecard types starting with NC57.
Workaround
Increase the packet size of the ISIS LSP of the router by adding a dummy loopback on the originating router and advertise it in ISIS.
Further Problem Description
This is how you can check the ISIS LSP length on any ISIS router.
RP/0/RP0/CPU0:R1#show isis database internal
IS-IS CORE (Level-2) Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime/Rcvd ATT/P/OL LSP Length
R1.00-00 * 0x00000099 0x317e 11139/* 0/0/0 270 <<<<<<
R2.00-00 0x00000007 0x6dbf 11416/15000 0/0/0 182
Total Level-2 LSP count: 2 Local Level-2 LSP count: 1
