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 22.214.171.124:33634 126.96.36.199:52701 188.8.131.52:44838 184.108.40.206:54497 220.127.116.11:61329 18.104.22.168:2527 22.214.171.124:14622 126.96.36.199:40696 188.8.131.52:26268 184.108.40.206:44076 220.127.116.11:25043 18.104.22.168:40963 ; to 22.214.171.124:53 ; 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 126.96.36.199, checking route to this ip address and found the nexthop is uplink device
<USG2120BSR>display fib 188.8.131.52
Route Entry Count: 1
Destination/Mask Nexthop Flag TimeStamp Interface TunnelID
0.0.0.0/0 184.108.40.206 GSU t Eth0/0/0 -
3. Checking the configuration on USG2100, found 220.127.116.11 which belongs vlanif 5 should connect to interface Ethernet1/0/4 whose current state is down.
ip address 18.104.22.168 255.255.255.248
port access vlan 5
Ethernet1/0/4 current state : DOWN
Line protocol current state : DOWN
4. The route on uplink device to 22.214.171.124 is USG2100, but USG2100 forwards the packets back to uplink router via default route because the interface which connect 126.96.36.199 is down. So, there is a route loop between USG2100 and uplink device.
5. This problem is resolved by configuring black hole route to 188.8.131.52 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.