As shown above, accessing internet through USG2100 is slow.
1. cpu-usage of USG2100 is 99%
2. There are warning messages in logbuffer as below:
%Mar 22 10:36:23 2013 USG2120BSR SEC/4/ATCKDF:AttackType:Udp flood attack; Receive Interface: Ethernet0/0/0 ; proto:UDP ; from 184.108.40.206:33634 220.127.116.11:52701 18.104.22.168:44838 22.214.171.124:54497 126.96.36.199:61329 188.8.131.52:2527 184.108.40.206:14622 220.127.116.11:40696 18.104.22.168:26268 22.214.171.124:44076 126.96.36.199:25043 188.8.131.52:40963 ; to 184.108.40.206:53 ; begin time :2013/03/22 10:35:55; end time: 2013/03/22 10:36:20; total packets: 199; max speed: 1014(packet/s);
1. Check the bandwidth and sessions on USG2100, and they are in normal range.
2. There are UDP attacks to 220.127.116.11, checking route to this ip address and found the nexthop is uplink device
<USG2120BSR>display fib 18.104.22.168
Route Entry Count: 1
Destination/Mask Nexthop Flag TimeStamp Interface TunnelID
0.0.0.0/0 22.214.171.124 GSU t Eth0/0/0 -
3. Checking the configuration on USG2100, found 126.96.36.199 which belongs vlanif 5 should connect to interface Ethernet1/0/4 whose current state is down.
ip address 188.8.131.52 255.255.255.248
port access vlan 5
Ethernet1/0/4 current state : DOWN
Line protocol current state : DOWN
4. The route on uplink device to 184.108.40.206 is USG2100, but USG2100 forwards the packets back to uplink router via default route because the interface which connect 220.127.116.11 is down. So, there is a route loop between USG2100 and uplink device.
5. This problem is resolved by configuring black hole route to 18.104.22.168 on USG2100
CPU usage too high usually caused by performance insufficient:
1. bandwidth/sessions/acl rules overload
2. route loop
4. ip duplicate
CPU usage abnormal usually caused by bandwidth/sessions/acl rules overload, route loop, attack, ip address duplicate and so on. When troubleshooting, please check them one by one.