A user terminal obtains an IP address from an ME60 for Internet access through PPPoE dialup. The ME60 originally imports UNRs in OSPF and advertises the UNRs to an NE5000E. Services are normal in this situation. After the ME60 advertises routes using BGP, the terminal fails to access the Internet.
1. Check whether the BGP peer relationship is properly established on the ME60.
<ME60>display bgp peer
BGP local router ID : 126.96.36.199
Local AS number : 65003
Total number of peers : 1 Peers in established state : 1
Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv
10.138.172.1 4 65003 419308 33923 0 0565h17m Established 18958
2. Run the display bgp routing-table peer 10.138.172.1 advertised-routes command on the ME60 to check whether BGP routes are properly advertised to the NE5000E. It is found that the BGP routes are properly advertised to the NE5000E.
3. Run the display bgp routing-table peer 188.8.131.52 received-routes command on the NE5000E to check whether routes can be properly received from the ME60.
<HUAWEI> display bgp routing-table peer 184.108.40.206 received-routes 220.127.116.11 24
BGP Local router ID is 10.138.172.1
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 18.104.22.168/24 22.214.171.124 0 100 0 ?
4. On the NE5000E, check that the service route received from the ME60 is a blackhole route.
<HUAWEI> display ip routing-table 126.96.36.199 24
Route Flags: R - relay, D - download to fib
Routing Tables: Public
Summary Count: 1
Destination/Mask Proto Pre Cost Flags Nexthop Interface
188.8.131.52/24 Static 200 0 D 0.0.0.0 NUll0
5. Check that the NE5000E is configured with a static blackhole route with the priority of 200 and the same mask/prefix as that of the BGP routes learned from the ME60. The BGP priority of the NE5000E is by default 255. As a result, the NE5000E preferentially matches the blackhole route with the priority of 200 over the service routes received from the ME60.
The NE5000E is configured with a static blackhole route with the same mask/prefix as that of the BGP routes learned from the ME60 but a higher priority than that of BGP routes. As a result, the NE5000E preferentially matches the blackhole route over the BGP routes, causing service interruptions.
1. Delete the blackhole route on the NE5000E.
undo ip route-static 184.108.40.206 24 NULL 0
2. On the NE5000E, change the priority of BGP routes to be greater than that of blackhole routes.
preference 20 20 20