某局点F5000-M 防火墙转发丢包问题排查经验案例

当前业务运行正常，UPF服务器往外ping 也是正常的，但是如果从锐捷交换机快ping 服务器会出现丢包问题，怀疑是锐捷交换机快ping机制问题导致，为了进一步定位，在防火墙上通过流量统计，看看是否丢在设备上。

流统测试结果：

acl advanced 3990
 description liutong
 rule 0 permit icmp source x.x.x.2 0 destination x.x.x.40 0 counting
 rule 5 permit icmp source x.x.x.40 0 destination x.x.x.2 0 counting
#
traffic classifier liutong operator and
 if-match acl 3990
#
traffic behavior liutong
 filter permit
#
qos policy liutong
 classifier liutong behavior liutong
#
interface Route-Aggregation1.51
 description uT:Global:internet_untrust
 qos apply policy liutong inbound
 qos apply policy liutong outbound
 vlan-type dot1q vid 51
#
interface Route-Aggregation1.52
 description dT:Global:internet_trust
 qos apply policy liutong inbound
 qos apply policy liutong outbound
 vlan-type dot1q vid 52

 远程查看现场锐捷交换机ping的方式，发现是每个包都会更改参数，因此在防火墙上每个包都会建立一条会话。并且现场流量跨框。
 <SC-CD-4L&01-11A07&16U-FW-F5000M-01>dis session table ipv4 destination-ip x.x.x.40 p i v
Slot 1:
Initiator:
  Source      IP/port: x.x.x.2/36860
  Destination IP/port: x.x.x.40/2048
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.51
  Source security zone: internet_Untrust
Responder:
  Source      IP/port: x.x.x.40/36860
  Destination IP/port: x.x.x.2/0
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.52
  Source security zone: internet_trust
State: ICMP_REQUEST
Application: ICMP
Rule ID: 15
Rule name: icmp_any
Start time: 2021-08-30 12:51:53  TTL: 28s
Initiator->Responder:            1 packets        128 bytes
Responder->Initiator:            0 packets          0 bytes

Initiator:
  Source      IP/port: x.x.x.2/36710
  Destination IP/port: x.x.x.40/2048
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.51
  Source security zone: internet_Untrust
Responder:
  Source      IP/port: x.x.x.40/36710
  Destination IP/port: x.x.x.2/0
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.52
  Source security zone: internet_trust
State: ICMP_REQUEST
Application: ICMP
Rule ID: 15
Rule name: icmp_any
Start time: 2021-08-30 12:51:38  TTL: 12s
Initiator->Responder:            1 packets        128 bytes
Responder->Initiator:            0 packets          0 bytes

Initiator:
  Source      IP/port: x.x.x.2/36677
  Destination IP/port: x.x.x.40/2048
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.51
  Source security zone: internet_Untrust
Responder:
  Source      IP/port: x.x.x.40/36677
  Destination IP/port: x.x.x.2/0
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.52
  Source security zone: internet_trust
State: ICMP_REQUEST
Application: ICMP
Rule ID: 15
Rule name: icmp_any
Start time: 2021-08-30 12:51:35  TTL: 9s
Initiator->Responder:            1 packets        128 bytes
Responder->Initiator:            0 packets          0 bytes

在这种情况下，会出现热备会话慢于ICMP回包的情况，通过debugging和会话也能看出。如下操作记录是先debugging看到后，再看的会话，可以看到回报上送二框后被丢弃。而查看备份会话的状态是非激活的状态，收到的报文个数也为0。说明报文先上了CPU处理，备份会话滞后导致无法匹配会话正常转发。

*Aug 30 12:55:07:882 2021 SC-CD-4L&01-11A07&16U-FW-F5000M-01 ASPF/7/PACKET: -COntext=1-Slot=2; The first packet was dropped by ASPF for invalid status. Src-ZOne=internet_trust, Dst-ZOne=internet_Untrust;If-In=Route-Aggregation1.52(155), If-Out=Route-Aggregation1.51(153); Packet Info:Src-IP=x.x.x.40, Dst-IP=x.x.x.2, VPN-Instance=none, Src-Port=37973, Dst-Port=0. Protocol=ICMP(1).
Initiator:
  Source      IP/port: x.x.x.2/37973
  Destination IP/port: x.x.x.40/2048
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.51
  Source security zone: internet_Untrust
Responder:
  Source      IP/port: x.x.x.40/37973
  Destination IP/port: x.x.x.2/0
  DS-Lite tunnel peer: -
  VPN instance/VLAN ID/Inline ID: -/-/-
  Protocol: ICMP(1)
  Inbound interface: Route-Aggregation1.52
  Source security zone: internet_trust
State: INACTIVE
Application: ICMP
Rule ID: 15
Rule name: icmp_any
Start time: 2021-08-30 12:55:07  TTL: 284s
Initiator->Responder:            0 packets          0 bytes
Responder->Initiator:            0 packets          0 bytes
现场情况特殊，正常PCping是使用同一条流，同一条流只会建立一条会话，现场锐捷交换机快速ping的方式比较特殊导致。处理方式有两种。
1. 组网改为主备模式，减少流量跨框情况。
2. 开启会话宽松，并放通反向策略。//不建议这种方式，会导致无法进行会话状态检查，安全性下降