BFD for BGP configuration example
Network requirements
As shown in Figure 68,
Configure OSPF as the IGP in AS 200.
Establish two IBGP connections between Switch A and Switch C. When both paths are working, Switch C adopts the path Switch A<—>Switch B<—>Switch C to exchange packets with network 1.1.1.0/24. Configure BFD over the path. If the path fails, BFD can quickly detect the failure and notify it to BGP. Then the path Switch A<—>Switch D<—>Switch C takes effect immediately.
Figure 68: Network diagram
Device | Interface | IP address | Device | Interface | IP address |
Switch A | Vlan-int100 | 3.0.1.1/24 | Switch C | Vlan-int101 | 3.0.2.2/24 |
Vlan-int200 | 2.0.1.1/24 | Vlan-int201 | 2.0.2.2/24 | ||
Switch B | Vlan-int100 | 3.0.1.2/24 | Switch D | Vlan-int200 | 2.0.1.2/24 |
Vlan-int101 | 3.0.2.1/24 | Vlan-int201 | 2.0.2.1/24 |
Configuration procedure
Configure IP addresses for interfaces. (Details not shown.)
Configure OSPF to make sure that Switch A and Switch C are reachable to each other. (Details not shown.)
Configure BGP on Switch A:
# Establish two IBGP connections to Switch C.
<SwitchA> system-view [SwitchA] bgp 200 [SwitchA-bgp] peer 3.0.2.2 as-number 200 [SwitchA-bgp] peer 2.0.2.2 as-number 200 [SwitchA-bgp] address-family ipv4 unicast [SwitchA-bgp-ipv4] peer 3.0.2.2 enable [SwitchA-bgp-ipv4] peer 2.0.2.2 enable [SwitchA-bgp-ipv4] quit [SwitchA-bgp] quit
# Create ACL 2000 to permit 1.1.1.0/24 to pass.
[SwitchA] acl number 2000 [SwitchA-acl-basic-2000] rule permit source 1.1.1.0 0.0.0.255 [SwitchA-acl-basic-2000] quit
# Create two route policies, apply_med_50 and apply_med_100. Policy apply_med_50 sets the MED for route 1.1.1.0/24 to 50. Policy apply_med_100 sets that to 100.
[SwitchA] route-policy apply_med_50 permit node 10 [SwitchA-route-policy-apply_med_50-10] if-match ip address acl 2000 [SwitchA-route-policy-apply_med_50-10] apply cost 50 [SwitchA-route-policy-apply_med_50-10] quit [SwitchA] route-policy apply_med_100 permit node 10 [SwitchA-route-policy-apply_med_100-10] if-match ip address acl 2000 [SwitchA-route-policy-apply_med_100-10] apply cost 100 [SwitchA-route-policy-apply_med_100-10] quit
# Apply routing policy apply_med_50 to routes outgoing to peer 3.0.2.2, and apply routing policy apply_med_100 to routes outgoing to peer 2.0.2.2.
[SwitchA] bgp 200 [SwitchA-bgp] address-family ipv4 unicast [SwitchA-bgp-ipv4] peer 3.0.2.2 route-policy apply_med_50 export [SwitchA-bgp-ipv4] peer 2.0.2.2 route-policy apply_med_100 export [SwitchA-bgp-ipv4] quit
# Enable BFD for peer 3.0.2.2.
[SwitchA-bgp] peer 3.0.2.2 bfd [SwitchA-bgp] quit
Configure BGP on Switch C:
# Establish two IBGP connections to Switch A.
<SwitchC> system-view [SwitchC] bgp 200 [SwitchC-bgp] peer 3.0.1.1 as-number 200 [SwitchC-bgp] peer 2.0.1.1 as-number 200 [SwitchC-bgp] address-family ipv4 unicast [SwitchC-bgp-ipv4] peer 3.0.1.1 enable [SwitchC-bgp-ipv4] peer 2.0.1.1 enable [SwitchC-bgp-ipv4] quit [SwitchC-bgp] quit
# Enable BFD for peer 3.0.1.1.
[SwitchC-bgp] peer 3.0.1.1 bfd [SwitchC-bgp] quit [SwitchC] quit
# Display detailed BFD session information on Switch C.
<SwitchC> display bfd session verbose Total Session Num: 1 Up Session Num: 1 Init Mode: Active IPv4 Session Working Under Ctrl Mode: Local Discr: 513 Remote Discr: 513 Source IP: 3.0.2.2 Destination IP: 3.0.1.1 Session State: Up Interface: N/A Min Tx Inter: 500ms Act Tx Inter: 500ms Min Rx Inter: 500ms Detect Inter: 2500ms Rx Count: 135 Tx Count: 135 Connect Type: Indirect Running Up for: 00:00:58 Hold Time: 2457ms Auth mode: None Detect Mode: Async Slot: 0 Protocol: BGP Diag Info: No DiagnosticThe output shows that a BFD session has been established between Switch A and Switch C.
# Display BGP peer information on Switch C.
<SwitchC> display bgp peer ipv4 BGP local router ID: 3.3.3.3 Local AS number: 200 Total number of peers: 2 Peers in established state: 2 Peer AS MsgRcvd MsgSent OutQ PrefRcv Up/Down State 2.0.1.1 200 4 5 0 0 00:01:55 Established 3.0.1.1 200 4 5 0 0 00:01:52 Established
The output shows that Switch C has established two BGP connections with Switch A, and both connections are in Established state.
# Display route 1.1.1.0/24 on Switch C.
<SwitchC> display ip routing-table 1.1.1.0 24 verbose Summary Count : 1 Destination: 1.1.1.0/24 Protocol: BGP Process ID: 0 SubProtID: 0x1 Age: 00h00m09s Cost: 50 Preference: 255 Tag: 0 State: Active Adv OrigTblID: 0x1 OrigVrf: default-vrf TableID: 0x2 OrigAs: 0 NBRID: 0x15000001 LastAs: 0 AttrID: 0x1 Neighbor: 3.0.1.1 Flags: 0x10060 OrigNextHop: 3.0.1.1 Label: NULL RealNextHop: 3.0.2.1 BkLabel: NULL BkNextHop: N/A Tunnel ID: Invalid Interface: Vlan-interface101 BkTunnel ID: Invalid BkInterface: N/AThe output shows that Switch C communicates with network 1.1.1.0/24 through the path Switch C<—>Switch B<—>Switch A.
# Break down the path Switch C<—>Switch B<—>Switch A and then display route 1.1.1.0/24 on Switch C.
<SwitchC> display ip routing-table 1.1.1.0 24 verbose Summary Count : 1 Destination: 1.1.1.0/24 Protocol: BGP Process ID: 0 SubProtID: 0x1 Age: 00h03m08s Cost: 100 Preference: 255 Tag: 0 State: Active Adv OrigTblID: 0x1 OrigVrf: default-vrf TableID: 0x2 OrigAs: 0 NBRID: 0x15000000 LastAs: 0 AttrID: 0x0 Neighbor: 2.0.1.1 Flags: 0x10060 OrigNextHop: 2.0.1.1 Label: NULL RealNextHop: 2.0.2.1 BkLabel: NULL BkNextHop: N/A Tunnel ID: Invalid Interface: Vlan-interface201 BkTunnel ID: Invalid BkInterface: N/AThe output shows that Switch C communicates with network 1.1.1.0/24 through the path Switch C<—>Switch D<—>Switch A.