Configure BGP ROUTE REFLECTOR on Cisco routers

How to configure BGP ROUTE REFLECTOR on Cisco routers?

SCALABILITY PROBLEMS WITH IBGP FULL MESH

When your network have grown and a full mesh isn't feasible n*(n-1)/2 where n = the number of iBGP speaking routers

If we have 200 routers in our network that would give us 19900 BGP sessions.

SOLUTIONS

Route Reflectors

Confederations

WHAT ARE BGP ROUTE REFLECTORS?

Using standard Internal Border Gateway Protocol (IBGP) configurations, all BGP systems within an Autonomous

System (AS) must peer with all other BGP systems, forming a full-mesh configuration. This presents scaling concerns, as all external information must be propagated/distributed to all BGP systems within the AS, resulting in far more

information being shared between the IBGP peers then is necessary. BGP Route Reflectors (RR) provides a mechanism for both minimizing the number of update messages transmitted within the AS, and reducing the amount of data that is

propagated in each message. The deployment of BGP Route Reflectors leads to much higher levels of network scalability.

A ROUTE REFLECTOR REFLECTS IBGP ROUTING INFORMATION

From clients to iBGP peers and other clients

From iBGP peers to clients

Never from iBGP peers to iBGP peers (as before)

Should not change the attributes

NEXT_HOP

AS_PATH

LOCAL_PREF

MED

CONFEDERATIONS

Another way of solving iBGP full mesh.

The idea behind confederations is to take one large AS and divide it into several smaller ones.

Non-members of the confederation see one AS, members of the confederation are divided into sub-AS's

One IGP must usually be run in the whole confederation to support connectivity.

LOCAL-PREF and NEXTHOP is preserved through the confederation.

BASIC CONFIGURATION OF ROUTER-A

A(config)# interface serial 1/0

A(config-if)# ip address 1.1.1.1 255.0.0.0

A(config-if)# no shutdown

A(config-if)# interface ethernet 2/0

A(config-if)# ip address 200.100.50.1 255.0.0.0

A(config-if)# no shutdown

BASIC CONFIGURATION OF ROUTER-B

B(config)# interface serial 1/0

B(config-if)# ip address 1.1.1.2 255.0.0.0

B(config-if)# no shutdown

B(config-if)# clock rate 64000

B(config)# interface serial 1/1

B(config-if)# ip address 2.1.1.1 255.0.0.0

B(config-if)# no shutdown

B(config-if)# clock rate 64000

BASIC CONFIGURATION OF ROUTER-C

C(config)# interface serial 1/1

C(config-if)# ip address 2.1.1.2 255.0.0.0

C(config-if)# no shutdown

C(config)# interface serial 1/0

C(config-if)# ip address 3.1.1.1 255.0.0.0

C(config-if)# no shutdown

BASIC CONFIGURATION OF ROUTER-D

D(config)# interface serial 1/1

D(config-if)# ip address 3.1.1.2 255.0.0.0

D(config-if)# no shutdown

RUNNING EBGP ON ROUTER-A

A(config)# router bgp 10

A(config-router)# no synchronization

A(config-router)# neighbor 1.1.1.2 remote-as 20

A(config-router)# network 200.100.50.0

RUNNING EBGP ON ROUTER-B

B(config)# router bgp 20

B(config-router)# no synchronization

B(config-router)# neighbor 1.1.1.1 remote-as 10

RUNNING OSPF ON ROUTER-B

B(config)# router ospf 1

B(config-router)# network 2.0.0.0 0.255.255.255 area 0

B(config-router)# network 1.0.0.0 0.255.255.255 area 0

RUNNING OSPF ON ROUTER-C

C(config)# router ospf 1

C(config-router)# network 2.0.0.0 255.255.255 area 0

C(config-router)# network 3.0.0.0 255.255.255 area 0

RUNNING OSPF ON ROUTER-D

C(config)# router ospf 1

C(config-router)# network 3.0.0.0 255.255.255 area 0

RUNNING IBGP ON ROUTER-B

B(config)# router bgp 20

B(config-router)# no synchronization

B(config-router)# neighbor 1.1.1.1remote-as 20

B(config-router)# neighbor 2.1.1.2remote-as 20

RUNNING IBGP ON ROUTER-C

C(config)# router bgp 20

C(config-router)# no synchronization

C(config-router)# neighbor 2.1.1.1 remote-as 20

C(config-router)# neighbor 3.1.1.2 remote-as 20

RUNNING IBGP ON ROUTER-D

D(config)# router bgp 20

D(config-router)# no synchronization

D(config-router)# neighbor 3.1.1.1 remote-as 20

APPLYING ROUTE-REFLECTOR ON ROUTER-C

C(config)# router bgp 20

C(config-router)# neighbor 2.1.1.1 route-reflector-client

C(config-router)# neighbor 3.1.1.2 route-reflector-client

C# clear ip bgp *

D# show ip bgp

Related Articles

How to configure RIP v2 step by step? RIP short for "Routing Information Protocol" is a routing protocol used to select the suitable route for packets with in network.. Read More...

How to configure static routes on Cisco routers? You can configure two types of routing on the router- static and dynamic to send the traffic to destination. Read More...

How to configure VLAN on a Cisco Switch? VLAN stands for virtual LAN and technically we can say, a VLAN is a broadcast domain created by switch. When managing a switch, the management domain is always VLAN 1, the default VLAN. All ports of switch are assigned to VLAN 1 by default. VLAN increase the performance of a network because it divide a network logically in different parts and limit the broadcasts. Read More...

How to configure VTP Client and Server? VTP (VLAN Trunking Protocol) is the protocol that propagates the information about which VLANs exist from one switch to another switch. If VTP did not provide this information, VLANs would have to be created on all switches individually in the network. Read More..

How to configure Trunking between VLANs with 802.1q? Trunk link is used to carry the different VLANs traffic on a single link. There are two different protocols are used for Ethernet trunking, 802. 1q and ISL. Trunking change the formatting of the packets. Read More...

How to configure Trunking between VLANs with ISL? Trunking is a technique to carry different VLAN traffic using point to point link between two devices. ISL (InterSwitch Link) is a cisco proprietary protocol can work with Ethernet token ring and Fddi also. Trunking changes the formatting of the packets. Read More...