H3C Technologies H3C S12500 Series Switches - Manual (Page 408)

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currently active route; Switch C<—>Switch D<—>Switch A, which is the backup route. Then the
link Switch C<—>Switch B<—>Switch A fails.
# Enable BFD debugging on Switch C.
debugging bfd scm
debugging bfd event
debugging bgp bfd
terminal monitor
terminal debugging
%Nov 5 11:42:24:172 2009 SwitchC BFD/5/BFD_CHANGE_FSM: Sess[3001::3/3000::1,
13/17,VLAN101,Ctrl], Sta: UP->DOWN, Diag: 1
%Nov 5 11:42:24:172 2009 SwitchC BGP/5/BGP_STATE_CHANGED: 3000::1 state is changed
from ESTABLISHED to IDLE.
*Nov 5 11:42:24:187 2009 SwitchC RM/6/RMDEBUG: BGP_BFD: Recv BFD DOWN msg, Src IP
3001::3, Dst IP 3000::1, Instance ID 0.
*Nov 5 11:42:24:187 2009 SwitchC RM/6/RMDEBUG: BGP_BFD: Reset BGP session 3000::1
for BFD session down.
*Nov 5 11:42:24:187 2009 SwitchC RM/6/RMDEBUG: BGP_BFD: Send DELETE msg to BFD,
Connection type DIRECT, Src IP 3001::3, Dst IP 3000::1, Instance ID 0.
The output shows that Switch C can quickly detect the failure on Switch B.
# Display routes destined for 1200::0/64 on Switch C.
display ipv6 routing-table 1200::0 64 verbose
Routing Table :
Summary Count : 1
Destination : 1200:: PrefixLength : 64
NextHop : 2000::1 Preference : 255
RelayNextHop : 2001::2 Tag : 0H
Neighbor : 2000::1 ProcessID : 0
Interface : Vlan-interface201 Protocol : BGP4+
State : Active Adv Cost : 100
Tunnel ID : 0x0 Label : NULL
Age : 4635sec
The output shows that Switch A and Switch C communicate through Switch D, and Switch C has
one route to reach network 1200::0/64, that is, Switch C<—>Switch D<—>Switch A.
Troubleshooting IPv6 BGP configuration
IPv6 BGP peer relationship not established
Symptom
Display BGP peer information by using the display bgp ipv6 peer command. The state of the connection
to the peer cannot become established.
Analysis
To become IPv6 BGP peers, any two routers must establish a TCP session using port 179 and exchange
open messages successfully.