静态路由Track与NQA联动不生效经验案例

某家庭宽带用户同时从ISP1和ISP2购买了宽带接入服务，ISP1通过DHCP方式向用户分配IP地址，网关地址是114.243.224.1，ISP2通过静态方式向用户分配地址，网关地址是123.122.96.1，CPE与BRAS之间经过的都是二层接入交换机，网关都在BRAS上面。ISP1和ISP2都是按流量计费的，但是ISP1的流量价格低于ISP2，用户希望在ISP1没有故障时流量全部通过ISP1转发，ISP1发生故障时自动切换到ISP2转发，既能实现高可靠性，又能降低宽带接入服务价格。

CPE设备的配置如下：
#
 sysname CPE
#
nqa entry admin test
 type icmp-echo
  destination ip 114.243.224.1
  frequency 100
  reaction 1 checked-element probe-fail threshold-type consecutive 5 action-type trigger-only
  ttl 1
#
 nqa schedule admin test start-time now lifetime forever
#
interface GigabitEthernet0/0
 ip address dhcp-alloc
#
interface GigabitEthernet0/1
 ip address 123.122.96.2 255.255.255.0
#
 ip route-static 0.0.0.0 0 114.243.224.1 track 1
 ip route-static 0.0.0.0 0 123.122.96.1 preference 80
#
 track 1 nqa entry admin test reaction 1
#
return

在某一天ISP1的BRAS到二层接入交换机之间的链路发生故障时，发现静态路由Track与NQA联动不生效，导致用户无法上网。

在CPE上display track 1，可以看到Track 1现在是Negative状态，但是display ip routing-table看到的缺省路由下一跳仍然是ISP1的网关地址。
[CPE]display track 1
Track ID: 1
  State: Negative
  Duration: 8 days 4 hours 20 minutes 10 seconds
  Notification delay: Positive 0, Negative 0 (in seconds)
  Tracked object:
    NQA entry: admin test
    Reaction: 1
    Remote IP/URL: 114.243.224.1
    Local IP: --
    Interface: --
[CPE]display ip routing-table
Destinations : 17       Routes : 17
Destination/Mask   Proto   Pre Cost        NextHop         Interface
0.0.0.0/0          Static  70  0           114.243.224.1   GE0/0
0.0.0.0/32         Direct  0   0           127.0.0.1       InLoop0
114.243.224.0/24   Direct  0   0           114.243.224.2   GE0/0
114.243.224.0/32   Direct  0   0           114.243.224.2   GE0/0
114.243.224.2/32   Direct  0   0           127.0.0.1       InLoop0
114.243.224.255/32 Direct  0   0           114.243.224.2   GE0/0
123.122.96.0/24    Direct  0   0           123.122.96.2    GE0/1
123.122.96.0/32    Direct  0   0           123.122.96.2    GE0/1
123.122.96.2/32    Direct  0   0           127.0.0.1       InLoop0
123.122.96.255/32  Direct  0   0           123.122.96.2    GE0/1
127.0.0.0/8        Direct  0   0           127.0.0.1       InLoop0
127.0.0.0/32       Direct  0   0           127.0.0.1       InLoop0
127.0.0.1/32       Direct  0   0           127.0.0.1       InLoop0
127.255.255.255/32 Direct  0   0           127.0.0.1       InLoop0
224.0.0.0/4        Direct  0   0           0.0.0.0         NULL0
224.0.0.0/24       Direct  0   0           0.0.0.0         NULL0
255.255.255.255/32 Direct  0   0           127.0.0.1       InLoop0

注意到此处缺省路由的Preference是70，但是ip route-static 0.0.0.0 0 114.243.224.1 track 1没有配置Preference，正常情况下Preference应该是60。
[CPE]display ip routing-table 0.0.0.0 0 verbose
Summary count : 1
Destination: 0.0.0.0/0
   Protocol: Static
 Process ID: 0
  SubProtID: 0x2                    Age: 196h20m10s
       Cost: 0               Preference: 70
      IpPre: N/A             QosLocalID: N/A
        Tag: 0                    State: Active Adv
  OrigTblID: 0x0                OrigVrf: default-vrf
    TableID: 0x2                 OrigAs: 0
      NibID: 0x11000000          LastAs: 0
     AttrID: 0xffffffff        Neighbor: 0.0.0.0
      Flags: 0x10060        OrigNextHop: 114.243.224.1
      Label: NULL           RealNextHop: 114.243.224.1
    BkLabel: NULL             BkNextHop: N/A
  Tunnel ID: Invalid          Interface: GigabitEthernet0/0
BkTunnel ID: Invalid        BkInterface: N/A
   FtnIndex: 0x0           TrafficIndex: N/A
  Connector: N/A                 PathID: 0x0

在CPE上display ip routing-table 0.0.0.0 0 verbose，可以看到SubProtID是0x2，查资料可知这条缺省路由是通过DHCP协议学到的，通过DHCP学到的路由Preference是70，小于下一跳是ISP2的网关地址的缺省路由的Preference是80，所以这条缺省路由被添加到了路由表。

在CPE上将下一跳是ISP2网关地址的缺省路由的Preference修改为65。
[CPE]ip route-static 0.0.0.0 0 123.122.96.1 preference 65
Route has been modified.
[CPE]display ip routing-table
Destinations : 17       Routes : 17
Destination/Mask   Proto   Pre Cost        NextHop         Interface
0.0.0.0/0          Static  60  0           114.243.224.1   GE0/0
0.0.0.0/32         Direct  0   0           127.0.0.1       InLoop0
114.243.224.0/24   Direct  0   0           114.243.224.2   GE0/0
114.243.224.0/32   Direct  0   0           114.243.224.2   GE0/0
114.243.224.2/32   Direct  0   0           127.0.0.1       InLoop0
114.243.224.255/32 Direct  0   0           114.243.224.2   GE0/0
123.122.96.0/24    Direct  0   0           123.122.96.2    GE0/1
123.122.96.0/32    Direct  0   0           123.122.96.2    GE0/1
123.122.96.2/32    Direct  0   0           127.0.0.1       InLoop0
123.122.96.255/32  Direct  0   0           123.122.96.2    GE0/1
127.0.0.0/8        Direct  0   0           127.0.0.1       InLoop0
127.0.0.0/32       Direct  0   0           127.0.0.1       InLoop0
127.0.0.1/32       Direct  0   0           127.0.0.1       InLoop0
127.255.255.255/32 Direct  0   0           127.0.0.1       InLoop0
224.0.0.0/4        Direct  0   0           0.0.0.0         NULL0
224.0.0.0/24       Direct  0   0           0.0.0.0         NULL0
255.255.255.255/32 Direct  0   0           127.0.0.1       InLoop0
%Jan 01 00:00:00:000 2011 CPE NQA/6/NQA_ENTRY_PROBE_RESULT: Reaction entry 1 of NQA entry admin-name admin operation-tag test: probe-fail.
[CPE]display ip routing-table
Destinations : 17       Routes : 17
Destination/Mask   Proto   Pre Cost        NextHop         Interface
0.0.0.0/0          Static  65  0           123.122.96.1    GE0/1
0.0.0.0/32         Direct  0   0           127.0.0.1       InLoop0
114.243.224.0/24   Direct  0   0           114.243.224.2   GE0/0
114.243.224.0/32   Direct  0   0           114.243.224.2   GE0/0
114.243.224.2/32   Direct  0   0           127.0.0.1       InLoop0
114.243.224.255/32 Direct  0   0           114.243.224.2   GE0/0
123.122.96.0/24    Direct  0   0           123.122.96.2    GE0/1
123.122.96.0/32    Direct  0   0           123.122.96.2    GE0/1
123.122.96.2/32    Direct  0   0           127.0.0.1       InLoop0
123.122.96.255/32  Direct  0   0           123.122.96.2    GE0/1
127.0.0.0/8        Direct  0   0           127.0.0.1       InLoop0
127.0.0.0/32       Direct  0   0           127.0.0.1       InLoop0
127.0.0.1/32       Direct  0   0           127.0.0.1       InLoop0
127.255.255.255/32 Direct  0   0           127.0.0.1       InLoop0
224.0.0.0/4        Direct  0   0           0.0.0.0         NULL0
224.0.0.0/24       Direct  0   0           0.0.0.0         NULL0
255.255.255.255/32 Direct  0   0           127.0.0.1       InLoop0

经过测试，可以解决问题。