Purpose
For BGP to run on a router in your network, you must define the local autonomous system (AS) number, configure at least one group, and include information about at least one peer in the group. If the peer is an EBGP peer, include the peer’s AS number. For all peers, include either the peer’s interface IP address or loopback (lo0) IP address. When configuring BGP on an interface, you must also include the family inet statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level.
Figure 14 illustrates the example configurations used in this topic.
Figure 14: BGP Configuration Topology
The network in Figure 14 consists of two directly connected ASs. IP addresses included in the network diagram are as follows:
All routers within each AS maintain an IBGP session between each router in that AS. R1 and R5 have an IBGP session through their loopback (lo0) interfaces: 10.0.0.1 and 10.0.05. R2, R3, R4, and R6 maintain IBGP sessions between each other through their loopback (lo0) interfaces: 10.0.0.2, 10.0.0.3, 10.0.0.4, and 10.0.0.6.
The two routers in AS 65001 each contain one EBGP link to AS 65002 (R2 and R4) over which they announce aggregated prefixes: 100.100/16. Routers at the edge of a network that communicate directly with routers in other networks are called border routers. Border routers use EBGP to exchange routing information between networks.
Adjacent BGP routers are referred to as neighbors or peers. Peers can be internal or external to the AS. Internal and external peers are configured slightly differently. In general, internal peers communicate using the loopback (lo0) interface, and external peers communicate through the shared interface. See Figure 14 for the loopback (lo0) and interface information.
To verify the BGP configuration of a router in your network, follow these steps:
To verify the BGP configuration of an internal router.
To verify the BGP configuration of an internal router, enter the following JUNOS command-line interface (CLI) command:
user@R3> show configuration
[...Output truncated...]
interfaces {
so-0/0/1 {
unit 0 {
family inet {
address 10.1.23.2/30;
}
family iso;
}
}
so-0/0/3 {
unit 0 {
family inet {
address 10.1.36.1/30;
}
family iso;
}
}
lo0 {
unit 0 {
family inet {
address 10.0.0.3/32;
}
family iso {
address 49.0002.1000.0000.0003.00;
}
}
}
}
routing-options {
[...Output truncated...]
router-id 10.0.0.3;
autonomous-system 65002;
}
protocols {
bgp {
group internal {
type internal;
local-address 10.0.0.3;
neighbor 10.0.0.2;
neighbor 10.0.0.4;
neighbor 10.0.0.6;
}
}
isis {
level 1 disable;
interface all {
level 2 metric 10;
}
interface lo0.0;
}
}
user@R6> show configuration |
[Output truncated...]
interfaces {
so-0/0/1 {
unit 0 {
family inet {
address 10.1.46.2/30;
}
family iso;
}
}
so-0/0/3 {
unit 0 {
family inet {
address 10.1.36.2/30;
}
family iso;
}
}
lo0 {
unit 0 {
family inet {
address 10.0.0.6/32;
}
family iso {
address 49.0003.1000.0000.0006.00;
}
}
}
}
routing-options {
[Output truncated...]
router-id 10.0.0.6;
autonomous-system 65002;
}
protocols {
bgp {
group internal {
type internal;
local-address 10.0.0.6;
neighbor 10.0.0.2;
neighbor 10.0.0.3;
neighbor 10.0.0.4;
}
}
isis {
level 1 disable;
interface all {
level 2 metric 10;
}
interface lo0.0;
}
}
The following sample output is for a BGP configuration on R3 in the network shown in Figure 14:
The sample output shows a basic BGP configuration on routers R3 and R6. The local AS (65002) and one group (internal) are configured on both routers. R3 has three internal peers—10.0.0.2, 10.0.0.4, and 10.0.0.6—included at the [protocols bgp group group] hierarchy level. R6 also has three internal peers: 10.0.0.2, 10.0.0.3, and 10.0.0.4. The underlying IGP protocol is Intermediate System-to-Intermediate System (IS-IS), and relevant interfaces are configured to run IS-IS.
Note that in this configuration the router ID is manually configured to avoid any duplicate router ID problems.
To verify the BGP configuration of a border router.
To verify the BGP configuration of a border router, enter the following JUNOS CLI operational mode command:
The following sample output is for a BGP configuration on two border routers from AS 65002 (R2 and R4) shown in Figure 14:
user@R2> show configuration
[...Output truncated...]
interfaces {
so-0/0/0 {
unit 0 {
family inet {
address 10.1.12.2/30;
}
family iso;
}
}
so-0/0/1 {
unit 0 {
family inet {
address 10.1.23.1/30;
}
family iso;
}
}
so-0/0/3 {
unit 0 {
family inet {
address 10.1.24.1/30;
}
family iso;
}
}
lo0 {
unit 0 {
family inet {
address 10.0.0.2/32;
}
family iso {
address 49.0002.1000.0000.0002.00;
}
}
}
}
routing-options {
[...Output truncated...]
router-id 10.0.0.2;
autonomous-system 65002;
}
protocols {
bgp {
group internal {
type internal;
export next-hop-self;
neighbor 10.0.0.3;
neighbor 10.0.0.4;
neighbor 10.0.0.6;
}
group toR1 {
type external;
import import-toR1;
peer-as 65001;
neighbor 10.1.12.1;
}
}
isis {
level 1 disable;
interface all {
level 2 metric 10;
}
interface lo0.0;
}
}
policy-options {
policy-statement next-hop-self {
term change-next-hop {
from neighbor 10.1.12.1;
then {
next-hop self;
}
}
}
policy-statement import-toR1 {
term 1 {
from {
route-filter 100.100.1.0/24 exact;
}
then {
local-preference 200;
}
}
}
user@R4> show configuration
[...Output truncated...]
interfaces {
so-0/0/1 {
unit 0 {
family inet {
address 10.1.46.1/30;
}
family iso;
}
}
so-0/0/2 {
unit 0 {
family inet {
address 10.1.45.1/30;
}
family iso;
}
}
so-0/0/3 {
unit 0 {
family inet {
address 10.1.24.2/30;
}
family iso;
}
}
lo0 {
unit 0 {
family inet {
address 10.0.0.4/32;
}
family iso {
address 49.0001.1000.0000.0004.00;
}
}
}
}
routing-options {
[...Output truncated...]
router-id 10.0.0.4;
autonomous-system 65002;
}
protocols {
bgp {
group internal {
type internal;
local-address 10.0.0.4;
export next-hop-self;
neighbor 10.0.0.2;
neighbor 10.0.0.3;
neighbor 10.0.0.6;
}
group toR5 {
type external;
peer-as 65001;
neighbor 10.1.45.2;
}
}
isis {
level 1 disable;
interface all {
level 2 metric 10;
}
interface lo0.0;
}
}
policy-options {
policy-statement next-hop-self {
term change-next-hop {
from neighbor 10.1.45.2;
then {
next-hop self;
}
}
}
The sample output shows a basic BGP configuration on border routers R2 and R4. Both routers have the AS (65002) included at the [routing-options] hierarchy level. Each router has two groups included at the [protocols bgp group group] hierarchy level. External peers are included in the external group, either toR1 or toR5, depending on the router. Internal peers are included in the internal group. The underlying IGP protocol is IS-IS on both routers, and relevant interfaces are configured to run IS-IS.
Note that in the configuration on both routers, the router ID is manually configured to avoid duplicate router ID problems, and the next-hop-self statement is included to avoid any BGP next-hop reachability problems.