BGP – Confederations


Goal:

  • Configure BGP confederations on topology with preconfigured OSPF,RIP routing inside sub-ASes of the confederation AS.

Required time: 120 minutes

Theoretical background:

Theoretical introduction into BGP:

Configuration and command reference for BGP,OSPF and EIGRP:

Topology:

BGP-Confederations

Configuration:

1) Check pre-configured settings

Before starting the configuration of BGP, make sure that routers configuration and network operation are correct. Topology is pre-configured so that every sub-AS has its own interior routing protocol configured
(OSPF, RIP) with passive interface between sub-ASes to prevent IGP connection. Use pingcommand to test connectivity. You should be able to ping all networks inside particular BGP sub-AS.

<RA>
{WAIT 20}
{ENTER}
enable
conf t
hostname RA
interface #RA:RA-RB#
ip address 10.1.0.1 255.255.255.252
no shutdown
exit
interface #RA:RC-RA#
ip address 10.2.0.2 255.255.255.252
no shutdown
exit
router rip
version 2
no auto-summary
network 10.1.0.0
network 10.2.0.0
</RA>
<RB>
{WAIT 20}
{ENTER}
enable
conf t
hostname RB
interface #RB:RA-RB#
ip address 10.1.0.2 255.255.255.252

no shutdown
exit
interface #RB:RB-RD#
ip address 11.0.0.1 255.255.255.252
no shutdown
exit
router rip
version 2
no auto-summary
network 10.1.0.0
passive-interface #RB:RB-RD#
exit
</RB>

<RC>
{WAIT 20}
{ENTER}
enable
conf t
hostname RC
interface #RC:RC-RA#
ip address 10.2.0.1 255.255.255.252
no shutdown
exit
interface #RC:RG-RC#
ip address 10.3.0.2 255.255.255.252

no shutdown
exit
interface loop0
ip address 172.16.1.1 255.255.255.0
no shutdown
exit
router rip
version 2
no auto-summary
network 10.2.0.0
network 172.16.1.0
passive-interface #RC:RG-RC#
exit
</RC>

<RD>
{WAIT 20}
{ENTER}
enable
conf t
hostname RD
interface #RD:RB-RD#
ip address 11.0.0.2 255.255.255.252
no shutdown
exit
interface #RD:RD-RE#
ip address 100.23.0.1 255.255.255.252
no shutdown
exit
interface loop0
ip address 111.0.1.1 255.255.255.0
no shutdown
exit
interface loop1
ip address 111.0.2.1 255.255.255.0
no shutdown
exit
router ospf 1
network 111.0.2.0 0.0.0.255 area 0
network 111.0.1.0 0.0.0.255 area 0
passive-interface #RD:RB-RD#
passive-interface #RD:RD-RE#
exit
</RD>
<RE>
{WAIT 20}
{ENTER}
enable
conf t
hostname RE
interface #RE:RE-RF#
ip address 12.0.0.1 255.255.255.252
no shutdown
exit
interface #RE:RD-RE#
ip address 100.23.0.2 255.255.255.252
no shutdown
exit
interface loop0
ip address 192.168.101.1 255.255.255.0
no shutdown
exit
router ospf 1
network 192.168.101.0 0.0.0.255 area 0
passive-interface #RE:RE-RF#
passive-interface #RE:RD-RE#
exit
</RE>
 
<RF>
{WAIT 20}
{ENTER}
enable
conf t
hostname RF
interface #RF:RF-RG#
ip address 10.4.0.1 255.255.255.252
no shutdown
exit
interface #RF:RE-RF#
ip address 12.0.0.2 255.255.255.252
no shutdown
exit

router ospf 1
network 10.4.0.0 0.0.0.3 area 0
passive-interface #RF:RE-RF#
exit
</RF>

<RG>
{WAIT 20}
{ENTER}
enable
conf t
hostname RG
interface #RG:RF-RG#
ip address 10.4.0.2 255.255.255.252
no shutdown
exit

interface #RG:RG-RC#
ip address 10.3.0.1 255.255.255.252
no shutdown
exit
interface loop0
ip address 192.168.1.1 255.255.255.0
no shutdown
exit
router ospf 1
network 192.168.1.0 0.0.0.255 area 0
network 10.3.0.0 0.0.0.3 area 0
passive-interface #RG:RG-RC#
exit
</RG>

2) Perform step 1 of function test

3) Configure BGP

Router RA:

Pay attention! BGP sessions must be full-meshed inside sub-AS, as shown in sub-AS 65101 configuration.

RA(config)#router bgp 65101; set confederation sub-AS number and start BGP processRA(config-router)#no synchronization ; disable synchronization between BGP and IGPRA(config-router)#bgp router-id 2.0.0.3; set unique BGP router IDRA(config-router)#bgp log-neighbor-changes; log neighbor changes

RA(config-router)#redistribute connected; redistribute interior networks via BGP to other ASes

RA(config-router)#bgp confederation identifier 100; set sub-AS 65101 as part of confederation 100

RA(config-router)#bgp confederation peers 65102; set another sub AS 65102 to be a peer in confederation 100

RA(config-router)#neighbor 10.1.0.2 remote-as 65101; set BGP neighbor to be part of the same sub AS to fulfill full mesh requirement

RA(config-router)#neighbor 10.2.0.1 remote-as 65101; set BGP neighbor to be part of the same sub AS to fulfill full mesh requirement

RA(config-router)#no auto-summary; do not summarize networks

Router RB:

RB(config)#router bgp 65101RB(config-router)#no synchronizationRB(config-router)#bgp router-id 2.0.0.1RB(config-router)#bgp log-neighbor-changes

RB(config-router)#redistribute connected

RB(config-router)#bgp confederation identifier 100

RB(config-router)#bgp confederation peers 65102

RB(config-router)#neighbor 11.0.0.2 remote-as 200; set BGP neighbor in external AS 200

RB(config-router)#neighbor 10.1.0.1 remote-as 65101; set BGP neighbor to be part of the same sub AS to fulfill full mesh requirement

RB(config-router)#neighbor 10.2.0.1 remote-as 65101; set BGP neighbor to be part of the same sub AS to fulfill full mesh requirement

RB(config-router)#no auto-summary

Similarly RC:

RC(config)#router bgp 65101RC(config-router)#no synchronizationRC(config-router)#bgp router-id 2.0.0.2RC(config-router)#bgp log-neighbor-changes

RC(config-router)#redistribute connected

RC(config-router)#bgp confederation identifier 100

RC(config-router)#bgp confederation peers 65102

RC(config-router)#neighbor 10.3.0.1 remote-as 65102

RC(config-router)#neighbor 10.1.0.2 remote-as 65101

RC(config-router)#neighbor 10.2.0.2 remote-as 65101

RC(config-router)#no auto-summary

Similarly for AS65201

Router RD:

RD(config)#router bgp 65201RD(config-router)#no synchronizationRD(config-router)#bgp router-id 5.0.0.2RD(config-router)#bgp log-neighbor-changes

RD(config-router)#redistribute connected

RD(config-router)#bgp confederation identifier 200

RD(config-router)#bgp confederation peers 65202

RD(config-router)#neighbor 11.0.0.1 remote-as 100

RD(config-router)#neighbor 100.23.0.2 remote-as 65202

RD(config-router)#no auto-summary

Similarly for AS65202

Router RE:

RE(config)#router bgp 65202RE(config-router)#no synchronizationRE(config-router)#bgp router-id 6.0.0.2RE(config-router)#bgp log-neighbor-changes

RE(config-router)#redistribute connected

RE(config-router)#bgp confederation identifier 200

RE(config-router)#bgp confederation peers 65201

RE(config-router)#neighbor 12.0.0.2 remote-as 100

RE(config-router)#neighbor 100.23.0.1 remote-as 65201

RE(config-router)#no auto-summary

Similarly for AS65102

Router RF:

RF(config)#router bgp 65102RF(config-router)#no synchronizationRF(config-router)#bgp router-id 4.0.0.1RF(config-router)#bgp log-neighbor-changes

RF(config-router)#redistribute connected

RF(config-router)#bgp confederation identifier 100

RF(config-router)#bgp confederation peers 65101

RF(config-router)#neighbor 12.0.0.1 remote-as 200

RF(config-router)#neighbor 10.4.0.2 remote-as 65102

RF(config-router)#no auto-summary

Router RG:

RG(config)#router bgp 65102RG(config-router)#no synchronizationRG(config-router)#bgp router-id 4.0.0.2RG(config-router)#bgp log-neighbor-changes

RG(config-router)#bgp confederation identifier 100

RG(config-router)#bgp confederation peers 65101

RG(config-router)#redistribute connected

RG(config-router)#neighbor 10.3.0.2 remote-as 65101

RG(config-router)#neighbor 10.4.0.1 remote-as 65102

RG(config-router)# auto-summary

Function test:

1) Display routing information before you configure BGP

Verify routing tables on all routers of the network using sh ip route command.
Verify BGP using sh ip bgp neighbor and sh ip bgp on RA and RD.

Rx# sh ip route

2) Display routing information with BGP configured

Verify routing tables on all routers of the network using sh ip route command.
Verify BGP using sh ip bgp neighbor and sh ip bgp on RA and RD.

Rx# sh ip route; x represents every router in topologyRx# sh ip bgp summaryRx# sh ip bgp neighborRx# sh ip bgp

Rx# sh ip ospf neighbors

3) Test connectivity

Test connectivity between AS100 and AS200. For example use ping command from RA to one of the interfaces on router RG. Also test connectivity to other routers.

RA# ping 100.23.0.2RA# traceroute 100.23.0.2

4) Compare routing tables in AS100 and AS200

BGP path in routing table will show confederation AS number instead of sub-AS numbers.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s