The configuration examples in this document were created and verified in a lab environment, and all the devices were started with the factory default configuration. When you are working on a live network, make sure you understand the potential impact of every command on your network.

This document assumes that you have basic knowledge of BGP.

Example: Configuring basic BGP

Network configuration

As shown in Figure 1, all routers run BGP. Run EBGP between Router A and Router B, and run IBGP between Router B and Router C so that Router C can access the network 8.1.1.0/24 connected to Router A.

Figure 1 Network diagram

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Analysis

To enable Router B to communicate with Router C through loopback interfaces, enable OSPF in AS 65009.

By default, BGP does not advertise local networks. To enable Router C to access the network 8.1.1.0/24 connected directly to Router A, perform the following tasks:

· Add network 8.1.1.0/24 to the BGP routing table of Router A.

· Add networks 3.1.1.0/24 and 9.1.1.0/24 to the BGP routing table of Router B.

Restrictions and guidelines

When you configure basic BGP, follow these restrictions and guidelines:

· Use loopback interfaces to establish IBGP connections to prevent route flapping caused by port state changes.

· Loopback interfaces are virtual interfaces. Use the peer connect-interface command to specify the loopback interface as the source interface for establishing BGP connections.

· The EBGP peers, Router A and Router B, are located in different ASs. Typically, their loopback interfaces are not reachable to each other, so the routers use directly connected interfaces to establish EBGP sessions.

Procedures

Configuring IP addresses for interfaces

1. Configure an IP address for Ten-GigabitEthernet 0/0/15.

<RouterA> system-view

[RouterA] interface ten-gigabitethernet 0/0/15

[RouterA-Ten-GigabitEthernet0/0/15] ip address 8.1.1.1 24

2. Configure IP addresses for other interfaces in the same way that Ten-GigabitEthernet 0/0/15 is configured. (Details not shown.)

Configuring IBGP connections

Configuring Router B

<RouterB> system-view

[RouterB] bgp 65009

[RouterB-bgp-default] router-id 2.2.2.2

[RouterB-bgp-default] peer 3.3.3.3 as-number 65009

[RouterB-bgp-default] peer 3.3.3.3 connect-interface Loopback 0

[RouterB-bgp-default] address-family ipv4 unicast

[RouterB-bgp-default-ipv4] peer 3.3.3.3 enable

[RouterB-bgp-default-ipv4] quit

[RouterB-bgp-default] quit

[RouterB] ospf 1

[RouterB-ospf-1] area 0

[RouterB-ospf-1-area-0.0.0.0] network 2.2.2.2 0.0.0.0

[RouterB-ospf-1-area-0.0.0.0] network 9.1.1.0 0.0.0.255

[RouterB-ospf-1-area-0.0.0.0] quit

[RouterB-ospf-1] quit

Configuring Router C

1. Configure IBGP settings on Router C.

<RouterC> system-view

[RouterC] bgp 65009

[RouterC-bgp-default] router-id 3.3.3.3

[RouterC-bgp-default] peer 2.2.2.2 as-number 65009

[RouterC-bgp-default] peer 2.2.2.2 connect-interface Loopback 0

[RouterC-bgp-default] address-family ipv4 unicast

[RouterC-bgp-default-ipv4] peer 2.2.2.2 enable

[RouterC-bgp-default-ipv4] quit

[RouterC-bgp-default] quit

[RouterC] ospf 1

[RouterC-ospf-1] area 0

[RouterC-ospf-1-area-0.0.0.0] network 3.3.3.3 0.0.0.0

[RouterC-ospf-1-area-0.0.0.0] network 9.1.1.0 0.0.0.255

[RouterC-ospf-1-area-0.0.0.0] quit

[RouterC-ospf-1] quit

2. Display BGP peer information on Router C.

[RouterC] display bgp peer ipv4

BGP local router ID : 3.3.3.3

Local AS number : 65009

Total number of peers : 1 Peers in established state : 1

Peer AS MsgRcvd MsgSent OutQ PrefRcv Up/Down State

2.2.2.2 65009 2 2 0 0 00:00:13 Established

The output shows that Router C has established an IBGP peer relationship with Router B.

Configuring EBGP connections

Configuring Router A

<RouterA> system-view

[RouterA] bgp 65008

[RouterA-bgp-default] router-id 1.1.1.1

[RouterA-bgp-default] peer 3.1.1.1 as-number 65009

[RouterA-bgp-default] address-family ipv4 unicast

[RouterA-bgp-default-ipv4] peer 3.1.1.1 enable

[RouterA-bgp-default-ipv4] network 8.1.1.0 24

[RouterA-bgp-default-ipv4] quit

[RouterA-bgp-default] quit

Configuring Router B

1. Configure EBGP settings on Router B.

[RouterB] bgp 65009

[RouterB-bgp-default] peer 3.1.1.2 as-number 65008

[RouterB-bgp-default] address-family ipv4 unicast

[RouterB-bgp-default-ipv4] peer 3.1.1.2 enable

[RouterB-bgp-default-ipv4] quit

[RouterB-bgp-default] quit

2. Display BGP peer information on Router B.

[RouterB] display bgp peer ipv4

BGP local router ID : 2.2.2.2

Local AS number : 65009

Total number of peers : 2 Peers in established state : 2

Peer AS MsgRcvd MsgSent OutQ PrefRcv Up/Down State

3.3.3.3 65009 4 4 0 0 00:02:49 Established

3.1.1.2 65008 2 2 0 0 00:00:05 Established

The output shows that Router B has established an IBGP peer relationship with Router C and an EBGP peer relationship with Router A.

3. Display the BGP routing table on Router A.

[RouterA] display bgp routing-table ipv4

Total number of routes: 1

BGP local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - dampened, h - history

s - suppressed, S - stale, i - internal, e – external

a - additional-path

Origin: i - IGP, e - EGP, ? – incomplete

Network NextHop MED LocPrf PrefVal Path/Ogn

* > 8.1.1.0/24 8.1.1.1 0 32768 i

4. Display the BGP routing table on Router B.

[RouterB] display bgp routing-table ipv4

Total number of routes: 1

BGP local router ID is 2.2.2.2

Status codes: * - valid, > - best, d - dampened, h - history

s - suppressed, S - stale, i - internal, e – external

a - additional-path

Origin: i - IGP, e - EGP, ? - incomplete

Network NextHop MED LocPrf PrefVal Path/Ogn

* >e 8.1.1.0/24 3.1.1.2 0 0 65008i

5. Display the BGP routing table on Router C.

[RouterC] display bgp routing-table ipv4

Total number of routes: 1

BGP local router ID is 3.3.3.3

Status codes: * - valid, > - best, d - dampened, h – history

s - suppressed, S - stale, i - internal, e – external

a - additional-path

Origin: i - IGP, e - EGP, ? - incomplete

Network NextHop MED LocPrf PrefVal Path/Ogn

i 8.1.1.0/24 3.1.1.2 0 100 0 65008i

The outputs show that Router A has learned no route to AS 65009, and Router C has learned network 8.1.1.0, but the next hop 3.1.1.2 is unreachable. As a result, the route is invalid.

Configuring BGP to redistribute direct routes on Router B

# Configure Router B.

[RouterB] bgp 65009

[RouterB-bgp-default] address-family ipv4 unicast

[RouterB-bgp-default-ipv4] network 3.1.1.0 24

[RouterB-bgp-default-ipv4] network 9.1.1.0 24

[RouterB-bgp-default-ipv4] quit

[RouterB-bgp-default] quit

# Display the BGP routing table on Router A.

[RouterA] display bgp routing-table ipv4

Total number of routes: 3

BGP local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - dampened, h - history

s - suppressed, S - stale, i - internal, e – external

a - additional-path

Origin: i - IGP, e - EGP, ? - incomplete

Network NextHop MED LocPrf PrefVal Path/Ogn

* >e 3.1.1.0/24 3.1.1.1 0 0 65009?

* > 8.1.1.0/24 8.1.1.1 0 32768 i

* >e 9.1.1.0/24 3.1.1.1 0 0 65009i

The output shows that route 9.1.1.0/24 has been added in Router A's routing table.

# Display the BGP routing table on Router C.

[RouterC] display bgp routing-table ipv4

Total number of routes: 3

BGP local router ID is 3.3.3.3

Status codes: * - valid, > - best, d - dampened, h - history

s - suppressed, S - stale, i - internal, e – external

a - additional-path

Origin: i - IGP, e - EGP, ? - incomplete

Network NextHop MED LocPrf PrefVal Path/Ogn

* >i 3.1.1.0/24 2.2.2.2 0 100 0 ?

* >i 8.1.1.0/24 3.1.1.2 0 100 0 65008i

* >i 9.1.1.0/24 2.2.2.2 0 100 0 i

The output shows that the route 8.1.1.0 becomes valid with the next hop as Router A.

Verifying the configuration

# Verify that Router C can ping 8.1.1.1.

[RouterC] ping 8.1.1.1

Ping 8.1.1.1 (8.1.1.1): 56 data bytes, press CTRL_C to break

56 bytes from 8.1.1.1: icmp_seq=0 ttl=254 time=10.000 ms

56 bytes from 8.1.1.1: icmp_seq=1 ttl=254 time=4.000 ms

56 bytes from 8.1.1.1: icmp_seq=2 ttl=254 time=4.000 ms

56 bytes from 8.1.1.1: icmp_seq=3 ttl=254 time=3.000 ms

56 bytes from 8.1.1.1: icmp_seq=4 ttl=254 time=3.000 ms

--- Ping statistics for 8.1.1.1 ---

5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss

round-trip min/avg/max/std-dev = 3.000/4.800/10.000/2.638 ms

Configuration files

Router A

interface Loopback0

ip address 1.1.1.1 255.255.255.255

interface ten-gigabitethernet 0/0/15

ip address 8.1.1.1 255.255.255.0

interface ten-gigabitethernet 0/0/16

ip address 3.1.1.2 255.255.255.0

bgp 65008

router-id 1.1.1.1

peer 3.1.1.1 as-number 65009

address-family ipv4 unicast

network 8.1.1.0 255.255.255.0

peer 3.1.1.1 enable

Router B

interface Loopback0

ip address 2.2.2.2 255.255.255.255

interface ten-gigabitethernet 0/0/15

ip address 3.1.1.1 255.255.255.0

interface ten-gigabitethernet 0/0/16

ip address 9.1.1.1 255.255.255.0

bgp 65009

router-id 2.2.2.2

peer 3.1.1.2 as-number 65008

peer 3.3.3.3 as-number 65009

peer 3.3.3.3 connect-interface Loopback0

address-family ipv4 unicast

network 3.1.1.0 24

network 9.1.1.0 24

peer 3.1.1.2 enable

peer 3.3.3.3 enable

ospf 1

area 0.0.0.0

network 2.2.2.2 0.0.0.0

network 9.1.1.0 0.0.0.255

Router C

interface Loopback0

ip address 3.3.3.3 255.255.255.255

interface ten-gigabitethernet 0/0/15

ip address 9.1.1.2 255.255.255.0

bgp 65009

router-id 3.3.3.3

peer 2.2.2.2 as-number 65009

peer 2.2.2.2 connect-interface Loopback0

address-family ipv4 unicast

peer 2.2.2.2 enable

ospf 1

area 0.0.0.0

network 3.3.3.3 0.0.0.0

network 9.1.1.0 0.0.0.255

Examples: Configuring BGP and IGP route redistribution

Network configuration

As shown in Figure 2, all devices of company A belong to AS 65008 and all devices of company B belong to AS 65009. Run EBGP between Router A and Router B, and run OSPF between Router B and Router C to allow communication only between networks 9.1.2.0/24 and 8.1.1.0/24.

Figure 2 Network diagram

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[RouterA] interface ten-gigabitethernet 0/0/15

[RouterA-Ten-GigabitEthernet0/0/15] ip address 8.1.1.1 255.255.255.0

2. Configure IP addresses for other interfaces in the same way that Ten-GigabitEthernet 0/0/15 is configured. (Details not shown.)

Enabling OSPF

Enable OSPF in AS 65009.

Configuring Router B

<RouterB> system-view

[RouterB] ospf 1

[RouterB-ospf-1] area 0

[RouterB-ospf-1-area-0.0.0.0] network 2.2.2.2 0.0.0.0

[RouterB-ospf-1-area-0.0.0.0] network 9.1.1.0 0.0.0.255

[RouterB-ospf-1-area-0.0.0.0] quit

[RouterB-ospf-1] quit

Configuring Router C

<RouterC> system-view

[RouterC] ospf 1

[RouterC-ospf-1] area 0

[RouterC-ospf-1-area-0.0.0.0] network 9.1.1.0 0.0.0.255

[RouterC-ospf-1-area-0.0.0.0] network 9.1.2.0 0.0.0.255

[RouterC-ospf-1-area-0.0.0.0] quit

[RouterC-ospf-1] quit

Configuring EBGP connections

Configure the EBGP connection and add network 8.1.1.0/24 to the BGP routing table of Router A.

Configuring Router A

<RouterA> system-view

[RouterA] bgp 65008

[RouterA-bgp-default] router-id 1.1.1.1

[RouterA-bgp-default] peer 3.1.1.1 as-number 65009

[RouterA-bgp-default] address-family ipv4 unicast

[RouterA-bgp-default-ipv4] peer 3.1.1.1 enable

[RouterA-bgp-default-ipv4] network 8.1.1.0 24

[RouterA-bgp-default-ipv4] quit

[RouterA-bgp-default] quit

Configuring Router B

[RouterB] bgp 65009

[RouterB-bgp-default] router-id 2.2.2.2

[RouterB-bgp-default] peer 3.1.1.2 as-number 65008

[RouterB-bgp-default] address-family ipv4 unicast

[RouterB-bgp-default-ipv4] peer 3.1.1.2 enable

Configuring BGP and IGP route redistribution

1. Configure route redistribution between BGP and OSPF on Router B.

[RouterB-bgp-default-ipv4] import-route ospf 1

[RouterB-bgp-default-ipv4] quit

[RouterB-bgp-default] quit

[RouterB] ospf 1

[RouterB-ospf-1] import-route bgp

[RouterB-ospf-1] quit

2. Display the BGP routing table on Router A.

[RouterA] display bgp routing-table ipv4

Total number of routes: 3

BGP local router ID is 1.1.1.1

Status codes: * - valid, > - best, d - dampened, h - history

s - suppressed, S - stale, i - internal, e – external

a - additional-path

Origin: i - IGP, e - EGP, ? - incomplete

Network NextHop MED LocPrf PrefVal Path/Ogn

* > 8.1.1.0/24 8.1.1.1 0 32768 i

* >e 9.1.2.0/24 3.1.1.1 1 0 65009?

The output shows that Router A has obtained the route to 9.1.2.0/24.

3. Display the OSPF routing table on Router C.

[RouterC] display ospf routing

OSPF Process 1 with Router ID 3.3.3.3

Routing Table

Topology base (MTID 0)

Routing for Network

Destination Cost Type NextHop AdvRouter Area

9.1.1.0/24 1 Transit 9.1.1.2 3.3.3.3 0.0.0.0

9.1.2.0/24 1 Stub 9.1.2.1 192.168.0.63 0.0.0.0

2.2.2.2/32 1 Stub 9.1.1.1 2.2.2.2 0.0.0.0

Routing for ASEs

Destination Cost Type Tag NextHop AdvRouter

8.1.1.0/24 1 Type2 1 9.1.1.1 2.2.2.2

Total Nets: 3

Intra Area: 2 Inter Area: 0 ASE: 1 NSSA: 0

The output shows that Router C has obtained the route to 8.1.1.0/24.

Verifying the configuration

# Verify that 8.1.1.1 can ping 9.1.2.1.

[RouterA] ping -a 8.1.1.1 9.1.2.1

Ping 9.1.2.1 (9.1.2.1) from 8.1.1.1: 56 data bytes, press CTRL_C to break

56 bytes from 9.1.2.1: icmp_seq=0 ttl=254 time=10.000 ms

56 bytes from 9.1.2.1: icmp_seq=1 ttl=254 time=12.000 ms

56 bytes from 9.1.2.1: icmp_seq=2 ttl=254 time=2.000 ms

56 bytes from 9.1.2.1: icmp_seq=3 ttl=254 time=7.000 ms

56 bytes from 9.1.2.1: icmp_seq=4 ttl=254 time=9.000 ms

--- Ping statistics for 9.1.2.1 ---

5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss

round-trip min/avg/max/std-dev = 2.000/8.000/12.000/3.406 ms

# Verify that 9.1.2.1 can ping 8.1.1.1.

[RouterC] ping -a 9.1.2.1 8.1.1.1

Ping 8.1.1.1 (8.1.1.1) from 9.1.2.1: 56 data bytes, press CTRL_C to break

56 bytes from 8.1.1.1: icmp_seq=0 ttl=254 time=9.000 ms

56 bytes from 8.1.1.1: icmp_seq=1 ttl=254 time=4.000 ms

56 bytes from 8.1.1.1: icmp_seq=2 ttl=254 time=3.000 ms

56 bytes from 8.1.1.1: icmp_seq=3 ttl=254 time=3.000 ms

56 bytes from 8.1.1.1: icmp_seq=4 ttl=254 time=3.000 ms

--- Ping statistics for 8.1.1.1 ---

5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss

round-trip min/avg/max/std-dev = 3.000/4.400/9.000/2.332 ms

# Verify that 8.1.2.1 cannot ping 9.1.2.1 or 9.1.3.1.

[RouterA] ping –a 8.1.2.1 9.1.2.1

Ping 9.1.2.1 (9.1.2.1) from 8.1.2.1: 56 data bytes, press CTRL_C to break

Request time out

--- Ping statistics for 9.1.2.1 ---

5 packet(s) transmitted, 0 packet(s) received, 100.0% packet loss

[RouterA] ping –a 8.1.2.1 9.1.3.1

Ping 9.1.3.1 (9.1.3.1) from 8.1.2.1: 56 data bytes, press CTRL_C to break

Request time out

--- Ping statistics for 9.1.3.1 ---

5 packet(s) transmitted, 0 packet(s) received, 100.0% packet loss

# Verify that 9.1.3.1 cannot ping 8.1.1.1 or 8.1.2.1.

[RouterC] ping –a 9.1.3.1 8.1.1.1

Ping 8.1.1.1 (8.1.1.1) from 9.1.3.1: 56 data bytes, press CTRL_C to break

Request time out

--- Ping statistics for 8.1.1.1 ---

5 packet(s) transmitted, 0 packet(s) received, 100.0% packet loss

[RouterC] ping –a 9.1.3.1 8.1.2.1

Ping 8.1.2.1 (8.1.2.1) from 9.1.3.1: 56 data bytes, press CTRL_C to break

Request time out

--- Ping statistics for 8.1.2.1 ---

5 packet(s) transmitted, 0 packet(s) received, 100.0% packet loss

Configuration files

Router A

interface Loopback0

ip address 1.1.1.1 255.255.255.255

interface ten-gigabitethernet 0/0/15

ip address 8.1.1.1 255.255.255.0

interface ten-gigabitethernet 0/0/16

ip address 3.1.1.2 255.255.255.0

interface ten-gigabitethernet 0/0/17

ip address 8.1.2.1 255.255.255.0

bgp 65008

router-id 1.1.1.1

peer 3.1.1.1 as-number 65009

address-family ipv4 unicast

network 8.1.1.0 255.255.255.0

peer 3.1.1.1 enable

Router B

interface Loopback0

ip address 2.2.2.2 255.255.255.255

interface ten-gigabitethernet 0/0/15

ip address 3.1.1.1 255.255.255.0

interface ten-gigabitethernet 0/0/16

ip address 9.1.1.1 255.255.255.0

bgp 65009

router-id 2.2.2.2

peer 3.1.1.2 as-number 65008

address-family ipv4 unicast

import-route ospf 1

peer 3.1.1.2 enable

ospf 1

import-route bgp

area 0.0.0.0

network 2.2.2.2 0.0.0.0

network 9.1.1.0 0.0.0.255

Router C

interface Loopback0

ip address 3.3.3.3 255.255.255.255

interface ten-gigabitethernet 0/0/15

ip address 9.1.1.2 255.255.255.0

interface ten-gigabitethernet 0/0/16

ip address 9.1.2.1 255.255.255.0

interface ten-gigabitethernet 0/0/17

ip address 9.1.3.1 255.255.255.0

ospf 1

area 0.0.0.0

network 9.1.1.0 0.0.0.255

network 9.1.2.0 0.0.0.255

02-Configuration Examples

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