Example for Configuring BGP Auto FRR

As shown in Figure 1, Router A belongs to AS 100; Router B, Router C, and Router D belong to AS 200. BGP Auto FRR needs to be configure so that the route from Router A to Router D can have backup forwarding information.

Figure 1 Networking diagram of configuring BGP Auto FRR

Configuration Roadmap

The configuration roadmap is as follows:

Configure EBGP connections between Router A and Router B and between Router A and Router C. Configure IBGP connections between Router D and Router B, and between Router D and Router C.
Configure routing policies on Router B and Router C to change the MED values of routes to Router D to facilitate route selection.
Configure BGP Auto FRR on Router A.

Data Preparation

To complete the configuration, you need the following data:

Router IDs and AS numbers of Router A, Router B, Router C, and Router D
Names of routing policies and MED values of routes on Router B and Router C

Procedure

Configure IP addresses for interfaces. The configuration details are not mentioned here.
Configure EBGP connections between Router A and Router B, and between Router A and Router C. Configure IBGP connections between Router B and Router D, and between Router C and Router D. # Configure EBGP connections on Router A.
```
<RouterA> system-view
```
```
[RouterA] bgp 100
```
```
[RouterA-bgp] router-id 1.1.1.1
```
```
[RouterA-bgp] peer 10.1.1.2 as-number 200
```
```
[RouterA-bgp] peer 10.2.1.2 as-number 200
```
NOTE:

The configurations of Router B and Router C are the same as that of Router A, and the detailed configurations are not mentioned here.

# Configure IBGP connections on Router D.
```
<RouterD> system-view
```
```
[RouterD] bgp 200
```
```
[RouterD-bgp] router-id 4.4.4.4
```
```
[RouterD-bgp] peer 10.3.1.1 as-number 200
```
```
[RouterD-bgp] peer 10.4.1.1 as-number 200
```
NOTE:

The configurations on Router B and Router C are similar, and the detailed configurations are not mentioned here.

Configuring routing policies on Router B and Router C so that the MED values of routes to Router D are different # Configure a routing policy on Router B.

<RouterB> system-view

[RouterB] route-policy rtb permit node 10

[RouterB-route-policy] apply cost 80

[RouterB-route-policy] quit

[RouterB] bgp 200

[RouterB-bgp] ipv4-family unicast

[RouterB-bgp-af-ipv4] peer 10.1.1.1 route-policy rtb export

# Configure a routing policy on Router C.

<RouterC> system-view

[RouterC] route-policy rtc permit node 10

[RouterC-route-policy] apply cost 120

[RouterC-route-policy] quit

[RouterC] bgp 200

[RouterC-bgp] ipv4-family unicast

[RouterC-bgp-af-ipv4] peer 10.2.1.1 route-policy rtc export

# Advertise a route to 4.4.4.4/32 on Router D.

[RouterD] bgp 200

[RouterD-bgp] ipv4-family unicast

[RouterD-bgp] network 4.4.4.4 32

# Run the display ip routing-table verbose command on Router A to check detailed information about the learned route to 4.4.4.4/32.

<RouterA> display ip routing-table 4.4.4.4 32 verbose
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 1

Destination: 4.4.4.4/32
     Protocol: BGP             Process ID: 0
   Preference: 255                   Cost: 80
      NextHop: 10.1.1.2         Neighbour: 10.1.1.2
        State: Active Adv             Age: 00h00m12s
          Tag: 0                 Priority: low
        Label: NULL               QoSInfo: 0x0
   IndirectID: 0x4
 RelayNextHop: 0.0.0.0          Interface: Pos1/0/0
     TunnelID: 0x0                  Flags:  D

Because the MED value of the route learnt from Router B is smaller, on Router A, the route to 4.4.4.4/32 selects the path RouterA→RouterB→RouterD. Because FRR is not configured, no backup information is available.

Enabling BGP Auto FRR on Router A, and checking the routing information # Enable BGP Auto FRR on Router A.

<RouterA> system-view

[RouterA] bgp 100

[RouterA-bgp] ipv4-family unicast

[RouterA-bgp-af-ipv4] auto-frr

# After the configuration, run the display ip routing-table verbose command on Router A to check the routing information.

<RouterA> display ip routing-table 4.4.4.4 32 verbose
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 1

Destination: 4.4.4.4/32
     Protocol: BGP             Process ID: 0
   Preference: 255                   Cost: 80
      NextHop: 10.1.1.2         Neighbour: 10.1.1.2
        State: Active Adv             Age: 00h52m45s
          Tag: 0                 Priority: low
        Label: NULL               QoSInfo: 0x0
   IndirectID: 0x4
 RelayNextHop: 0.0.0.0          Interface: Pos1/0/0
     TunnelID: 0x0                  Flags:  D
    BkNextHop: 10.2.1.2       BkInterface: Pos2/0/0
      BkLabel: NULL           SecTunnelID: 0x0
 BkPETunnelID: 0x0        BkPESecTunnelID: 0x0
 BkIndirectID: 0x2

The preceding information shows that Router A has a backup next hop and a backup outbound interface to 4.4.4.4/32.

Configuration Files

Configuration file of Router A

#
 sysname RouterA
#
interface Pos1/0/0
 ip address 10.1.1.1 255.255.255.0
#
interface Pos2/0/0
  ip address 10.2.1.1 255.255.255.0
#
bgp 100
 router-id 1.1.1.1
 peer 10.1.1.2 as-number 200
 peer 10.2.1.2 as-number 200
#
 ipv4-family unicast
    auto-frr
#
return

Configuration file of Router B

#
 sysname RouterB
#
interface Pos1/0/0
 ip address 10.1.1.2 255.255.255.0
#
interface Pos2/0/0
  ip address 10.3.1.1 255.255.255.0
#
bgp 200
 router-id 2.2.2.2
 peer 10.1.1.1 as-number 100
 peer 10.3.1.2 as-number 200
#
 ipv4-family unicast 
    peer 10.1.1.1 route-policy rtb export
#
route-policy rtb permit node 10
 apply cost 80
#
return

Configuration file of Router C

#
 sysname RouterC
#
interface Pos1/0/0
 ip address 10.2.1.2 255.255.255.0
#
interface Pos2/0/0
 ip address 10.4.1.1 255.255.255.0
#
bgp 200
 router-id 3.3.3.3
 peer 10.2.1.1 as-number 100
 peer 10.4.1.2 as-number 200
 #
 ipv4-family unicast
    peer 10.2.1.1 route-policy rtc export
#
route-policy rtc permit node 10
 apply cost 120
#
return

Configuration file of Router D

#
 sysname RouterD
#
interface Pos1/0/0
 ip address 10.3.1.2 255.255.255.0
#
interface Pos2/0/0
  ip address 10.4.1.2 255.255.255.0
#
interface LoopBack1
 ip address 4.4.4.4 255.255.255.255
#
bgp 200
 router-id 4.4.4.4
 peer 10.3.1.1 as-number 200
 peer 10.4.1.1 as-number 200
 #
 ipv4-family unicast
  network 4.4.4.4 255.255.255.255
#
return

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