Hello,
I would like to understand why a network scan (nmap doing a ping scan) going to a L2VSN could cause control plane to exhibit high CPU.
Obviously we see a lot of ARPs here (broadcast) as the firewall interface toward destination LAN tries to resolve members of the scanned subnet (here: /21).
All switches which have an endpoint configured in that i-sid (flex-uni) experience high CPU in bcmINTR process and also messages about CPP Tx queue getting saturated.
We do use arp inspection but the NNI is explicity set to trusted. The fabric switches themselves do not have an IP interface in that VLAN, it's all L2VSN with flex-uni.
Why is this kind of traffic affecting the control plane so much? (tried on 5520 running FE 8.10.3.0 and 9.1.3.0)
Thx
1 2025-10-10T22:55:20.893+02:00 XXX CP1 - 0x0002474c - 00000000 GlobalRouter CPU INFO CPP: 60 percent of fbufs are in use: 1829 in Tx queue, 13 in RxQueue0 0 in RxQueue1 0 in RxQueue2 0 in RxQueue3 0 in RxQueue4 0 in RxQueue5 0 in RxQueue6 0 in RxQueue7 Pkts in Q0 (type): 13(10)
...
Sat Oct 11 2025 02:17:22.785013 1 cpp.c :6081[lcy-te][1154-1742]cbcp-main.x:cppProcRxFrame :CPP: cppProcRxFrame: dst=ff-ff-ff-ff-ff-ff src=00-09-0f-09-02-1e typ=0806 IP OR ARP len=56 arrived from 04-01:02:03:04:05:06 updated_port=TX-NNI vid=0x19d pid=2 code=0000 qos=0 PEH 0x019d0000, PktProcCode 0
Sat Oct 11 2025 02:17:22.785074 1 cpp.c :1595[lcy-ve][1154-1742]cbcp-main.x:cppTxFrame :CPP: cppTxFrame: dst=ff-ff-ff-ff-ff-ff src=00-09-0f-09-02-1e typ=0806 port 1/1 pid=2
Sat Oct 11 2025 02:17:22.785120 1 cpp.c :1595[lcy-ve][1154-1742]cbcp-main.x:cppTxFrame :CPP: cppTxFrame: dst=ff-ff-ff-ff-ff-ff src=00-09-0f-09-02-1e typ=0806 port 1/2 pid=2
Sat Oct 11 2025 02:17:22.785192 1 cpp.c :1595[lcy-ve][1154-1742]cbcp-main.x:cppTxFrame :CPP: cppTxFrame: dst=ff-ff-ff-ff-ff-ff src=00-09-0f-09-02-1e typ=0806 port 1/3 pid=2
Sat Oct 11 2025 02:17:22.785229 1 cpp.c :1595[lcy-ve][1154-1742]cbcp-main.x:cppTxFrame :CPP: cppTxFrame: dst=ff-ff-ff-ff-ff-ff src=00-09-0f-09-02-1e typ=0806 port 1/4 pid=2
Sat Oct 11 2025 02:17:22.785265 1 cpp.c :1595[lcy-ve][1154-1742]cbcp-main.x:cppTxFrame :CPP: cppTxFrame: dst=ff-ff-ff-ff-ff-ff src=00-09-0f-09-02-1e typ=0806 port 1/6 pid=2
